Knowledge of migratory bird requirements is critical to developing conservation plans for vulnerable migratory species. This study aimed to determine the migration routes, wintering areas, habitat uses, and mortalities of adult Chinese Egrets (Egretta eulophotata). Sixty adult Chinese Egrets (31 females and 29 males) on an uninhabited offshore breeding island in Dalian, China were tracked using GPS satellite transmitters. GPS locations recorded at 2 h intervals from June 2019 to August 2020 were used for analysis. A total of 44 and 17 tracked adults completed their autumn and spring migrations, respectively. Compared with autumn migration, tracked adults displayed more diverse routes, higher number of stopover sites, slower migration speed, and longer migration duration in the spring. Results indicated that migrant birds had different behavioral strategies during the two migratory seasons. The spring migration duration and stopover duration for females were significantly longer than those for males. A positive correlation existed between the spring arrival and spring departure dates, as well as between the spring arrival date and stopover duration. This finding indicated that the egrets that arrived early at the breeding grounds left the wintering areas early and had a shorter stopover duration. Adult birds preferred intertidal wetlands, woodlands, and aquaculture ponds during migration. During the wintering period, adults preferred offshore islands, intertidal wetlands, and aquaculture ponds. Adult Chinese Egrets showed a relatively low survival rate compared with most other common ardeid species. Dead specimens were found in aquaculture ponds, indicating human disturbance as the main cause of death of this vulnerable species. These results highlighted the importance of resolving conflicts between egrets and human-made aquaculture wetlands and protecting intertidal flats and offshore islands in natural wetlands through international cooperation. Our results contributed to the hitherto unknown annual spatiotemporal migration patterns of adult Chinese Egrets, thereby providing an important basis for the conservation of this vulnerable species.
Reintroduction has become a common conservation management tool to restore endangered species in their historical range. However, many attempts have failed to establish self-sustaining populations in the wild. The success of reintroductions could be improved by varying release strategies. Therefore, it is vital to determine the factors influencing reintroduction outcomes. To better understand the post-release settlement and to optimize the release strategy of the Crested Ibis (Nipponia nippon), we quantified the effects of age, sex, acclimation duration, and the timing of release events on post-release survival and dispersal distance for the released Crested Ibis in Tongchuan City, Shaanxi Province, using a generalized linear mixed effect modeling approach. Our results indicate that 40–56.3% of the released individuals survived the first year following release. Mortality was attributable to flight collisions, starvation, disease, and unknown reasons. The post-release survival probability of ibises showed a negative association with age (estimate = −0.186; 95% CI: −0.350 to −0.022; P = 0.026), and post-release dispersal distance was affected by the timing of release event (estimate = 0.718; 95% CI: 0.025 to 1.253; P = 0.042). However, sex and acclimation period duration did not cause detectable differences in post-release survival probability and dispersal distance. Based on our results, optimal release strategies for establishing a reintroduced population of the Crested Ibis include: (1) release of sub-adults biased and sex ratio balanced initial groups; (2) release during the non-breeding season; and (3) food supplementation immediately after release.
Raptors share a common predatory lifestyle, but are different in food preferences and hunting behavior. The grip force and talons' grasping capabilities are fundamentally crucial for subduing and killing their prey to feed, but the abilities and differences to generate force are less known. In this study, the entire pelvic muscles were dissected with the muscle mass and fibre length measured and physiological cross-sectional area counted in the Common Kestrel (Falco tinnunculus), Eurasian Sparrowhawk (Accipiter nisus), and Long-eared Owl (Asio otus). Statistical tests were performed to explore the possible differences in architectural parameters among species. These species were same in distributing the greatest proportion of muscle mass to the shank region and the digital flexor functional group, allocating more than 60% muscle mass in relation to total single leg muscle mass to the same seven individual muscles including flexor digitorum longus (FDL), flexor hallucis longus (FHL), and tibialis cranialis (TC) which are three major muscles responsible for talon closure. Interspecies differentiations were most present in the shank and tarsus instead of other regions of the leg, which might reflect their difference in hunting mode and foot use. Greater force-generation capacity of FHL and some anatomical features suggest that digits 1 and 2 work together as an efficiently vise-like set, playing more critical role than digits 3–4 in foraging of diurnal raptors but to a different degree. In accordance with zygodactyl foot morphology, each digit of the Long-eared Owl plays a subequal role when hunting, evidenced by anatomical and architectural features. Because of its unique insertion to the base of the pygostyle, the striking numerical difference in the development of M. caudofemoralis was possibly related to raptors' flight behavior and feeding ecology. Concluded from anatomical and architectural aspects, the similarities and differences of the hindlimb musculature were correlated to common predatory lifestyle and different foraging behaviors in three raptor species. These results illustrated the underlying myological basis for the functional capacities of the leg muscles and may provide additional information useful in further biomechanical investigation and computer simulation.
Climate change impacts bird migration phenology, causing changes in departure and arrival dates, leading to potential mismatches between migration and other key seasonal constraints. While the impacts of climate change on arrival at breeding grounds have been relatively well documented, little is known about the impacts of climate change on post-breeding migration, especially at stopover sites. Here we use long-term (11 years) banding data (11,118 captures) from 7 species at Mai Po Marshes Nature Reserve in Hong Kong, a key stopover site for migratory birds along the East Asian–Australasian Flyway, to describe long-term changes in migration phenology and to compare observed changes to annual weather variation. We also examine changes in wing length over a longer time period (1985–2020) as wing length often correlates positively with migration distance. We found that observed changes in migratory phenology vary by species; three species had later estimated arrival (by 1.8 days per year), peak (by 2.6 days per year) or departure (by 2.5 days per year), one showed an earlier peak date (by 1.8 days per year) and two showed longer duration of passage (2.7 days longer and 3.2 days longer per year). Three species exhibited no long-term change in migration phenology. For two of the four species with shifting phenology, temperature was an important predictor of changing peak date, departure dates and duration of passage. Wing length was shorter in three species and longer in two species, but these changes did not correlate with observed phenological changes. The complex changes observed here are indicative of the challenges concerning the detection of climate change in migratory stopover sites. Continued monitoring and a better understanding of the dynamics of all sites in the migratory pathway will aid conservation of these species under global change.
Hummingbird species have closely evolved with the plants they feed on, which is confirmed by their often tight ecological relationships in natural settings. Hummingbird-plant interactions are of interest for research areas such as ecology, evolution, and even agriculture, as they usually inform on the conservation status of interacting species assemblages, and its disappearance may precede the population extinction of the species involved in the interaction. In Chile, there are nine hummingbird species, which interact with a large and diverse number of angiosperm species in forest, desert, and mountain range environments. The motivation to perform this review is to systematize the available information regarding the flowering plants visited by hummingbird species in Chile, to present some basic plant-hummingbird pollination network metrics, and on this basis to identify the components of the plant-hummingbird relationships in need of further research. A plant-hummingbird metanetwork revealed a low connectance value, low niche overlap, and strong modularity among species. However, the fact that most species present a strong allopatric distribution across Chile, suggests that network structure results mostly from the history of colonization rather than from ecological organization. Nowadays, the main threats to Chilean hummingbirds are anthropogenic disturbance and climate change, which disrupt hummingbird-plant interactions, leading to unpredictable ecological consequences at the community level. Long periods of drought may reduce the resource base for hummingbirds, with dramatic consequences for the maintenance of bird and plant populations.
Gut microbiota and host interactions co-evolve and develop into stably adapted microbial communities and play vital roles in maintaining the health of organisms. Diet is supposed to be an important driver of differences in gut microbiota, but previous studies would commonly use literature depictions, which are essential but inaccurate, to explain the effects of diet on the gut microbiota of wild birds. In this study, we collected intestinal samples from five sympatric flycatchers to compare the gut microbial differences using bacterial 16S rRNA genes from Illumina MiSeq platform. Over 1,642,482 quality-filtered sequences from 18 16S rRNA libraries were obtained and distinct compositions and diversities of gut microbiota were found in five flycatchers. Their gut microbiota is mainly from the four bacterial phyla of Proteobacteria, Firmicutes, Actinomycetes, and Bacteroidetes, but at the genus level showed a significant difference. Functional predictions revealed that the metabolic capacity of the gut microbiota of five flycatchers is greatly distinguished at KEGG level 3. And multiple food fragments showed a significant correlation with gut microbiota. Besides, the significant differences in the specific composition of the diets of the five insectivorous flycatchers indicated the differentiation of dietary niches. The study of the gut microbiota and feeding habits of sympatric flycatchers would increase the understanding of the gut microbial diversity of wild birds, and also improve our cognition of the co-evolution and co-adaptation within the host gut microbiota relations.
Nest predation is an essential factor affecting bird population density, reproductive ecology and life cycle. However, there are still contradictory results about how nest predation pressure changes with urbanization. One of the reasons for the controversy is that previous studies often use artificial nests to investigate nest predation, but the result of artificial nests is often biased and contrary to that of natural nests. Therefore, it is important to perform nest predation experiments simultaneously with both natural and artificial nests. In this study, we examined the change of nest predation pressure on the Chinese Bulbul (Pycnonotus sinensis) along the urbanization gradient in Hangzhou, China. We detected 148 natural nests of Chinese Bulbuls and continuously monitored them in two continuous breeding seasons from 2012 to 2013. After the breeding season, we placed artificial eggs in natural nests of Chinese Bulbuls to investigate the changes in nest predation pressure and used infrared cameras to record the predators. We then calculated the urbanization synthetic index (USI) as the measure of the degree of urbanization and examined its relationship with nest predation pressure. We found that no matter whether natural nests or artificial eggs were used, the nest predation pressure always decreased significantly with the degree of urbanization. The average height of shrubs within 10 m of the nest differed significantly between the predated and unpredated nests, which also affected the risk of nest predation. Our study highlights the importance of using natural and artificial nests simultaneously to conduct nest predation experiments, which can reduce the bias or errors caused by only using artificial nests. We also recommend the use of infrared cameras in future nest predation studies, which has obvious advantages in monitoring and identifying potential predators.
In addition to landscape changes, urbanization also brings about changes in environmental factors that can affect wildlife. Despite the common referral in the published literature to multiple environmental factors such as light and noise pollution, there is a gap in knowledge about their combined impact. We developed a multidimensional environmental framework to assess the effect of urbanization and multiple environmental factors (light, noise, and temperature) on life-history traits and breeding success of Barn Swallows (Hirundo rustica) across rural to urban gradients in four locations spanning over 2500 km from North to South China. Over a single breeding season, we measured these environmental factors nearby nests and quantified landscape urbanization over a 1 km2 radius. We then analysed the relationships between these multiple environmental factors through a principal component analysis and conducted spatially explicit linear-mixed effects models to assess their effect on life-history traits and breeding success. We were particularly interested in understanding whether and how Barn Swallows were able to adapt to such environmental conditions associated with urbanization. The results show that there is significant variation in the exposure to environmental conditions experienced by Barn Swallows breeding across urbanization gradients in China. These changes and their effects are complex due to the behavioural responses ameliorating potential negative effects by selecting nesting sites that minimize exposure to environmental factors. However, significant relationships between landscape urbanization, exposure to environmental factors, and life-history traits such as laying date and clutch size were pervasive. Still, the impact on breeding success was, at least in our sample, negligible, suggesting that Barn Swallows are extremely adaptable to a wide range of environmental features.
The responses of ground-dwelling birds to heat and cold stress encompass a variety of behavioural, physiological and even morphological mechanisms. However, the role of glabrous skin in this respect has been marginally addressed so far. The Helmeted Guineafowl (Numida meleagris) is a landfowl distributed across Sub-Saharan Africa with eight traditionally recognised extant subspecies. Among the most prominent morphological traits underlying intraspecific variability are size and pigmentation of the bare throat skin (or sack), which might be related to the different habitats and environmental conditions across its wide range. In order to explore the Helmeted Guineafowl range-wide sack variation and pigmentation in relation to thermoregulation and sexual signalling, we collected morphometric and environmental information for N. m. coronata integrating field data with the inspection of photographic material encompassing seven subspecies and environmental information from their habitats. Field data evidenced that sack size was significantly correlated with ambient temperature, thus pointing to a likely involvement of the throat sack in thermoregulation. When the pictorial data from all subspecies were pooled, sack size correlated negatively with biomass, rainfall and humidity, while a positive correlation was found with annual solar irradiation. Sack size correlated positively with monthly temperature variation among the blue-throated subspecies from southern Africa as opposed to the black-throated subspecies ranging north to Zambia and Mozambique. Still, in this latter group the sack was often larger during winter months, possibly to maximise solar radiation absorbance. Noteworthy, sack size was related to sex dimorphism in two subspecies. Sack morphology and colour in the Helmeted Guineafowl likely modulate body temperature by evaporative cooling or heating upon needs, but in some subspecies it is also seemingly related to sexual signalling. Additional studies are needed to fully understand the multifunctionality of this important morphological feature in this species.
Worldwide, tropical montane cloud forest is one of the most important and biodiverse ecosystems; however, it is also one of those most threatened by anthropic activities. These activities lead to a fragmented, deforested landscape with narrow riparian forest strips immersed in an agricultural matrix dominated by pastures. Here, we characterize the interaction network between frugivorous birds and zoochorous plants in riparian strips of cloud forest in deforested landscapes of Central Veracruz, Mexico. To characterize the network of this mutualistic interaction, we estimated network- and species-level metrics using the Bipartite R package. Nestedness, modularity and robustness were used to describe network structure. Centrality measures of degree, closeness, betweenness centrality and their relative contribution to nestedness were used to determine the importance of each bird/plant species to the network's structure. This interaction network has 24 species of birds and 30 species of plants, with low connectance (0.11), low nestedness (11.53), and intermediate but not significant modularity (0.49). The bird species most important to network stability were Chlorospingus flavopectus, Myadestes occidentalis, and Catharus mexicanus. The most important plants were Conostegia xalapensis, C. arborea, and Rubus ulmifolius. Network robustness varied from 0.36 to 0.86 and its stability is compromised when species of birds or plants with the highest values of centrality are removed, with plant removal more detrimental. Riparian strips of cloud forest crossing deforested areas maintain a relatively rich set of birds that disperse the seeds of many forest plants, thus they are crucial to the preservation of this mutualistic network in anthropic landscapes. Network stability is severely undermined by the loss of any of the few species — whether birds or plants — with high centrality values. The most important plants for this stability are pioneer tree and shrub species that provide food for several bird species, and they are also crucial to cloud forest regeneration. A worrisome finding is that some of the bird species most important to network stability are also among the most sought-after as ornamental birds by illegal collectors in the region.
An accurate and updated regional bird species checklist is the foundation for biodiversity research and conservation. However, with ongoing climate and landscape changes, tracking the distributions of bird species is challenging, and expert-curated species lists are often limited regarding survey area and timeliness. Birdwatching in China is becoming increasingly popular, and observations recorded by citizen birders are quickly increasing as well. Assessing the value of these data for improving regional species lists and studying bird distribution needs a detailed and quantitative comparison of citizen science data and expert-curated data. We collected observation reports from the China Bird Report Center, the largest online open platform for sharing bird sightings in China. We focused on reports from 2016 to 2019 in Shaanxi Province. For expert-curated species lists, we used three sources: the latest bird field guide published by local ornithologists, the province list from Avibase, and a list generated from overlaying distribution range from BirdLife International with the outline of Shaanxi Province. In addition, we also compared the bird sighting coordinates with the species distribution maps from BirdLife International. Surprisingly, species checklists from different sources have considerable discrepancies, even among lists based on expert knowledge. Including birdwatching data, there are 616 bird species in total, but less than half of the species (294) appear in all checklists, and 17.2% of species are unique to one list. One hundred sixty-three species lack birdwatching records, but birdwatching identified 39 species new to the province. One hundred thirty-six bird species have sighting locations outside the distribution ranges from BirdLife International, suggesting that updates might be needed. The data also showed a clear trend of bird species shifting to higher latitudes than their traditional distributions. While being inadequate for generating a regional species checklist on its own, birdwatching data in China can be a valuable source for complementing expert knowledge. In particular, the coordinate information of bird sighting can help track species distribution shifts. On the other hand, comparing expert-curated lists to birdwatching data can generate a species list for targeted birdwatching and monitoring, which will improve the quality of the birdwatching data in the future.
Begging brings benefits and costs for nestling birds: it can indicate their needs to their parents, but it can also be a cue used by predators to find the nest. The costs, like many variables related to nest predation, can be specific to what kinds of predators are present and their auditory capabilities. These costs and benefits could also be affected by human noise, as noise could disrupt communication to parents and eavesdropping by predators, although human-produced noise might be easily ignored if predators can hear high-frequency components of the begging. We studied nest predation on a generalist bird, the Red-whiskered Bulbul (Pycnonotus jocosus), in a tropical forest in which there are many kinds of nest predators, including birds, mammals and reptiles. In 20 natural nests in which artificial eggs were placed, and subsequently in 140 artificial nests, we broadcast recordings of begging nestlings, with and without traffic noise, at two volume levels. We hypothesized that playback would increase predation relative to a silent control, and that mixing in traffic noise with the begging would decrease predation, as the begging signal was masked. However, we hypothesized that some predators, particularly small mammals with sensitive high-frequency hearing, might ignore the traffic noise. We found that predation was lowest for the control treatment, and lower for treatments mixed with traffic noise than for those without it. Small mammals, however, showed an unexpected pattern, displaying less nest predation in the treatments with traffic noise. Our results demonstrate the human-associated noise can disturb nest predators and influence which kinds of predators use begging to locate nests.
Genetic diversity is one of the three dimensions of biodiversity and fundamental to various life forms on the Earth. Understanding the distribution pattern of genetic diversity and its driving forces has been an important topic in ecology, biogeography and conservation biology since the last decade. We investigated the genetic diversity pattern of passerine birds in the Mountains of Southwest China, a global biodiversity hotspot with the highest species richness of birds in the entire Eurasia, and explored the influencing forces of environmental variables on genetic diversity. We compiled 1189 Cytochrome b sequences of 27 passerine species from 152 geographic sites, covering the range of Mountains of Southwest China and its adjoining areas. We generated genetic diversity distribution maps using a grid-cell method based on nucleotide diversity and haplotype diversity indices. We further analyzed the variation pattern of the two indices along latitudinal, longitudinal, and elevational gradients. The correlations between the two indices and environmental variables were also evaluated. The nucleotide diversity hotspots were mostly located in the southern Hengduan Mountains, while for haplotype diversity, three hotspots were detected: the southeast edge of the Qinghai-Tibetan Plateau, the southern Hengduan Mountains and the Qinling Mountains. There was no monotonic increasing or decreasing pattern in nucleotide diversity or haplotype diversity along latitudinal, longitudinal or elevational gradients except for altitudinal range. Correlation and model selection analyses detected multiple environmental variables in driving genetic diversity patterns, including temperature, precipitation, vegetation, human influence, longitude and altitude range. Similar to the pattern of species richness, the nucleotide diversity pattern of passerine birds in the Mountains of Southwest China presents a decreasing trend from southwest to northeast, while the haplotype diversity pattern is more likely decreased from west to east. Our results indicate that the distribution pattern of genetic diversity may be derived from the complex topography and diverse microclimates in the Mountains of Southwest China.
Brood parasites, such as the Common Cuckoo (Cuculus canorus), rely on manipulating hosts from other species to raise their offspring. Selection should favor individuals that are able to identify and choose host nests that closely match the incubation stage of their own eggs. While intuitive, and supported by the findings of numerous long-term monitoring studies, experimental evidence of this remains sparse. By using video monitoring, we used three experimental groups to explore whether Common Cuckoos preferentially choose host Oriental Reed Warbler (Acrocephalus orientalis) nests that are early in their laying cycle. We found that Common Cuckoos preferentially parasitize nests of the host Oriental Reed Warbler that are earlier in their laying (less vs. more eggs) or nesting cycle (eggs vs. chicks), and videos of our experiments provide direct insights into their decision making process. Our results provide strong experimental evidence that Common Cuckoos are able to assess nesting stage and strategically choose nests that increase the likelihood of successful parasitism.
Biodiversity has been subjected to increasing anthropogenic pressures. It is critical to understand the different processes that govern community assembly and species coexistence under biogeographic processes and anthropogenic events. Pheasants (Aves: Phasianidae) are highly threatened birds and China supports the richest pheasant species worldwide. Unravelling the spatial patterns and underlying factors associated with multi-dimensional biodiversity of species richness (SR), functional diversity (FD), and phylogenetic diversity (PD) of pheasants in China is helpful to understand not only the processes that govern pheasant community assembly and species coexistence, but also pheasant biodiversity conservation. We used a total of 45 pheasant species in China and analyzed the SR, FD, PD, and functional and phylogenetic structures by integrating species distribution maps, functional traits and phylogenies based on 50 km × 50 km grid cells. We further used simultaneous autoregressive (SAR) models to explore the factors that determined these patterns. The southern Qinghai-Tibetan Plateau (QTP), Hengduan Mountains, southwestern Mountains, the east of the Qilian Mountains, the Qinling, southern China displayed higher SR, FD, and PD, which were determined by elevation, habitat heterogeneity, temperature seasonality, and vegetation cover. Elevation primarily determined the functional and phylogenetic structures of the pheasant communities. Assemblages in the highlands were marked by functional and phylogenetic clustering, particularly in the QTP, whereas the lowlands in eastern China comprised community overdispersion. Clustered pheasant assemblages were composed of young lineages. Patterns of functional and phylogenetic structures and richness-controlled functional and phylogenetic diversity differed between regions, suggesting that phylogenetic structures are not a good proxy for identifying functional structures. We revealed the significant role of elevation in pheasant community assemblages in China. Highlands interacted with community clustering, whereas lowlands interacted with overdispersion, supporting the environmental filtering hypothesis. Biogeographical drivers other than anthropogenic factor determined biodiversity of pheasants at the present scale of China. This study provides complementary background resources for multi-dimensional pheasant biodiversity and provides insights into avian biodiversity patterns in China.
Facing climate and land use change, a species' ability to successfully adapt to changing environments is crucial for its survival. Extensive drainage and intensification of agriculture and forestry set wetlands and associated species at risk of population declines. The population of Common Cranes (Grus grus) has experienced considerable fluctuations over the last century. Despite increasing population numbers, hatching success seemed to have decreased over the last years. The aim of this study was to identify factors influencing hatching success and nest survival of Common Cranes based on analyses of long-term individual-based monitoring data from northeastern Germany and evaluate the species ability to adapt to changing environments. Hatching success decreased over the course of the study period from 0.75 to 0.55. Surprisingly, nest survival and hatching success did not vary across different nesting habitats, whereas factors such as female age, timing of nest initiation and breeding pair density were found to have significant effects on hatching success. Older females showed higher hatching success, even though the proportion of unhatched eggs was highest in females aged 20 years or older. Early nest initiation had a positive effect on hatching success. Water levels are more favorable early in the nesting season, whereas increasing evaporation with time causes water levels to decrease, granting easier access for predators. Independently of female age, hatching success decreased with increasing numbers of breeding pairs within a 2-km radius around a nesting site. High population densities intensify competition for resources and promote intraspecific interactions, affecting reproductive outcome negatively. This study gives first insights into mechanisms behind population regulation in Common Cranes, highlighting the importance of population dynamics and individual features. We suggest to further investigate density dependent effects including landscape and habitat features as well as reproductive success in terms of chick survival, since successfully raising juveniles is crucial for a species survival.
Populations at the low latitude limits of a species range (rear-edge populations) are often considered more vulnerable to climate change. However, their ability to track different environmental settings at a regional scale has been widely overlooked, although this may be relevant to accurately assess their adaptive capacity to cope with ongoing changes. Here we tested whether the endemic African Chaffinch (Fringilla coelebs africana) tracks environmental changes (e.g. decreasing temperatures, snow cover) by rearranging their numbers between seasons (spring vs. winter) along the altitude gradients of its northwestern African range. We additionally tested whether these seasonal changes in abundance were paralleled by morphological variation, suggesting a process of population diversification. We assessed African Chaffinch abundance in tree covered farmland and woodland sites distributed along an altitude gradient in spring and winter. In addition, we captured and measured chaffinches within the study gradient to explore the patterns of morphological variation. Our results showed that chaffinches shifted to lowlands from snow covered highlands during winter. In addition, highland individuals showed longer and more concave wings than their lowland counterparts. These morphological traits are usually related to flight efficiency in migratory birds, which suggest the presence of altitudinal movements aimed to track the environmental seasonality caused by orography. These results suggest a potential role of altitudinal seasonality as a driver of regional diversification within the African Chaffinch populations, which could be occurring in other North African avian species given their relatively high endemicity in the region. The evolutionary and conservation implications of these displacements have been often overlooked despite they can shape the adaptive capacity of rear-edge bird populations to face the ongoing environmental changes in this peripheral area of the Palearctic.
Several ectoparasites parasitise nestlings decreasing their body condition, growth and survival. To minimise any loss of fitness due to ectoparasites, birds have developed a wide variety of defence mechanisms, potentially including hatching asynchrony. According to the Tasty Chick Hypothesis (TCH), the cost of parasitism would be reduced if ectoparasites tend to eat on less immunocompetent nestlings, typically the last-hatched chick in asynchronously hatched broods, as they are in poor body condition. Two predictions of the TCH are that immune capacity is lower in smaller nestlings than in larger ones and that parasites should provoke a more negative effect on smaller nestlings. Here, we test these predictions in a population of Blue Tits (Cyanistes caeruleus) whose broods are parasitised by Hen Fleas (Ceratophyllus gallinae) and Blowflies (Protocalliphora azurea). We recorded the presence of both ectoparasites and analysed the immunocompetence (number of leucocytes per 10,000 erythrocytes and cutaneous immune response to phytohaemagglutinin) and body condition of smaller and larger nestlings within individual broods. The leucocyte count was higher in smaller nestlings than in larger ones, whereas the cutaneous immune response did not differ between smaller and larger nestlings. Smaller nestlings, but not larger nestlings, had lower body mass when fleas were present. Blowflies, by contrast, had no detectable negative effect on nestlings. Overall, our findings provide partial support to the TCH. Lower immune capacity in smaller nestlings than in larger ones was not supported, but Hen Fleas seemed to negatively impact on smaller nestlings more than on larger ones.
The hypothalamic-pituitary-gonadal (HPG) axis ubiquitously regulates seasonal reproduction, following the rhythmicity of a suite of environmental cues. Birds display prominent seasonal variations in gonad size regulated by two hypothalamic peptides, gonadotropin-releasing hormone-1 (GnRH-I) and gonadotropin-inhibiting hormone (GnIH). How multi-brooded avian species adjust GnRH-I and GnIH to regulate gonadal morphology seasonally remains largely unknown. Here, we studied the variations in the hypothalamic immunoreactivity (ir) of GnRH-I and GnIH, gonadal proliferation, and apoptosis in a typical multi-brooded species, the Eurasian Tree Sparrow (Passer montanus), across the pre-breeding (PB), first breeding (FB), second breeding (SB), pre-basic molt (PM), and wintering stages (WS). Our results showed that both sexes had higher preoptic area (POA)-GnRH-I-ir but lower paraventricular nucleus (PVN)-GnIH-ir neurons during the breeding stages (FB and SB) relative to other life-history stages, with no significant differences between two broods. The testes and ovaries were significantly larger during the breeding stages. Testicular volume increased during the two broods due to anincreased diameter of seminiferous tubules. Furthermore, there were more testicular apoptotic cells in PB and WS stages than in breeding stages, and in PB stage than in PM stage. Males had higher POA-GnRH-I expression than females during the breeding stages, but both sexes had comparable PVN-GnIH expression throughout the annual cycle. Both sexes of the sparrows may undergo a similar pattern of life-history stage-dependent variation in the hypothalamic GnRH-I, GnIH, and gonadal morphology, except that during breeding stages, males may display higher expression of POA-GnRH-I relative to females. The higher expression of POA-GnRH-I-ir in breeding male sparrows may be critical for male-dependent parental care.
The taxonomy of the Blue-crowned Laughingthrush (Garrulax courtoisi) and its relationship with the Yellow-throated Laughingthrush (G. galbanus) and G. c. simaoensis, a range-restricted subspecies in China, has not been fully elucidated. So the taxonomic status and system evolution of the three taxa G.courtoisi, G. galbanus and G. c. simaoensis need to be reclarified. Two gene sequences myoglobin (MYO) and the mitochondrial cytochrome coxidase subunit I (COI) were combined to investigate the phylogenetic relationships among courtoisi, simaoensis and galbanus, genetic data, combining with morphological, ecological and acoustic data were used to comb out the classification status and divergence level of the three taxa. Significant genetic and morphological differentiations (body size and plumage coloration) were detected between courtoisi and galbanus. However, no notable and reliable differences between the courtoisi and simaoensis were detected. The courtoisi, simaoensis and galbanus are clearly isolated in geographical distribution as a result of differing altitudes, climate conditions and habitats. The courtoisi has characteristic preference for nest location compared with galbanus. In addition, the results of song analysis also indicated that there are differences in maximum frequency between courtoisi and galbanus. G. courtoisi was confirmed to be an independent species based on genetic, morphological, geographical, ecological and vocal characteristics, and the validity of simaoensis as a subspecies still need more evidence. This study further confirmed the high conservation value of Blue-crowned Laughingthrush. In addition, due to the genetic differences between Simao and Wuyuan populations, this should be fully considered in future protection strategies.
Bird photography is a popular and growing form of ecotourism that contributes to the economic growth of local communities, but its disturbance to bird reproduction remains understudied. We worked in a tropical forest of southern China, which has experienced a sharp increase in the number of photographers in recent years. We compared nests that were photographed and those that were not, in their nest predation and parental feeding rates. Including nests of 42 species, the results demonstrate that the predation rate of nests that were not photographed (incubation stage: 43.3% of 194 nests; nestling stage: 34.5% of 110 nests) was significantly higher than that of photographed ones (incubation: 2.4% of 83 nests; nestling: 11.1% of 81 nests). Among different nest types, open cup nests in shrub and trees were most affected by photography, in both incubation and nestling stages. Of five factors investigated, including three natural factors (nest stage, structure and position), and two anthropogenic factors (photography and distance to forest edge), only photographic disturbance and nest structure had significant effects (open nests had higher predation). The feeding frequency at nests when photographers were present was not strongly different from when they were not present. Human activity therefore had no negative effects on the birds, but showed a positive effect on their nesting success, in terms of reducing nest predation rates. However, there needs to be further assessment of other aspects of nesting (e.g., clutch size, duration of nestlings in nests), and other kinds of stress responses (e.g., hormonal changes), before the total effect of bird photography can be understood.
Natural hybridization, which often occurs between closely related species exhibiting sympatric or parapatric distributions, is an important source of genetic variation within populations. The closely related Jankowski's Bunting (Emberiza jankowskii) and Meadow Bunting (E. cioides) are similar in morphology and genetics, occupy overlapping niches, and are sympatric in eastern Inner Mongolia. Previous studies have reported trans-species polymorphisms of alleles between the two species, as well as an unexpectedly high genetic diversity of the endangered E. jankowskii. We speculate that introgressive hybridization has occurred between the two species and contributed to the additional unexpected variation to E. jankowskii. We used mitochondrial NADH dehydrogenase subunit 2 (ND2) gene and 15 nuclear microsatellite markers to compare the genetic diversity of E. jankowskii and E. cioides, and inferred the origin of trans-species polymorphisms between the two species by phylogenetic reconstruction and Bayesian cluster analysis. The two species could be clearly distinguished by population cluster analysis. Despite the large number of mutational differences, we still detected sharing of major haplotypes and the presence of hybrids between the two species. Our study confirmed that weak introgressive hybridization has occurred between sympatric E. jankowskii and E. cioides, which may be mediated by female E. cioides individuals, and that interspecific introgression has contributed to the maintenance of high genetic diversity in E. jankowskii. While being wary of the potential negative effects of introgressive hybridization, we suggest that expanding the habitat of E. jankowskii remains the most effective conservation strategy at present.
The Chinese Monal (Lophophorus lhuysii) is an alpine-obligate galliform species of global conservation priority. It has been listed as a first class protected wildlife species in China, requiring conservation actions during the 14th Five-Year Plan period. However, the diet composition of Chinese Monal and its seasonal variations have rarely been studied, constraining the effective conservation of the species. Here, we investigated the plant diet composition of the Chinese Monal and its seasonal variations using a DNA metabarcoding approach on fecal samples. We collected 190 fecal samples of the Chinese Monals from the central Qionglai Mountains located in China, and analyzed the plant diet of this species using a DNA metabarcoding approach. Taxonomic profiling of higher plants in the fecal samples was performed using the second internal transcribed spacer (ITS2) amplicon. Downstream analyses, including rarefaction curves, nonmetric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA), were used to explore the seasonal variations in diet composition. The Chinese Monal foraged a wide range of plant recipes composed of 35 families and 83 genera throughout the year, with Brassicaceae, Apiaceae, and Poaceae as the dominant families, and Cardamine as the dominant genus. The species consumed plants from 62 genera from 28 families during the breeding season (n = 81) and 66 genera from 31 families during the non-breeding season (n = 109). Further, the plant diet composition significantly varied between the breeding and non-breeding seasons, especially for the frequency of occurrence and relative read abundances at genus level. Our study analyzed the plant diet of the Chinese Monal at a high resolution for the first time, and the results revealed that the seasonal variations in its plant diet composition was adapted to plant phenology and foraging strategy. Fritillaria species, a previously confirmed important food resource for the Chinese Monal, were not detected in any fecal samples, potentially due to overharvesting of Fritillaria bulbs for Traditional Chinese Medicine. Therefore, we highly recommend further restriction of herb gathering in Chinese Monal habitats to facilitate the conservation of this endangered species. Altogether, our study enriches essential ecological information for the Chinese Monal and also provides insights into conservation management for this endangered species.
Sex differences in plumage color are common in bird species. Some bird species are regarded as sexually monochromatic in human visual systems, and in recent years, some species are found to be of cryptic (to human) sexual dichromatism by spectrophotometric techniques. However, the functions of plumage color are still less understood in these species. Here, we focused on plumage color traits in the Chestnut Thrush (Turdus rubrocanus), which is considered as a sexually monochromatic bird by human observers. We used spectrometer analyses and avian visual modeling to investigate the color traits of males and females, and whether these color traits are involved in assortative mating. We found that Chestnut Thrush showed sexual dichromatism in bill, throat and wing, and pairs mated assortatively with colorations of throat, chest, crown and wing. We also found that color of tarsus was different between two consecutive years. These results revealed that Chestnut Thrush is sexually dichromatic in the avian visual system, and plumage color traits play important roles in mate choice.
To avoid unnecessary energy expenditures in territorial defense, many species (e.g., insects, amphibians, birds, and mammals) have developed the capability to distinguish between different intruder types using visual, acoustic, and/or chemical signals. Determining the mechanism used for intruder recognition is key to understanding the dynamics of territorial behaviors. In birds that use vocalizations for territorial defense, the frequency and duration of vocalizations or the familiarity with the intruder may be the main mechanism used for intruder recognition. Here, we conducted a playback experiment with territorial White-eared Ground-sparrows (Melozone leucotis), to analyze if territorial pairs recognize intruders using frequency and duration characteristics (a bird's response is based on how structurally similar the intruders' duets are to their own) or by familiarity with the intruders (neighbors vs. non-neighbors). We focused on duets because this species uses duets exclusively for territorial defense. We broadcasted a duet from a territorial neighbor, two duets from non-neighbors (with different frequency and duration characteristics), and a duet from a control species in 39 territorial pair from three populations. During playback we measured five behavioral responses: latency of the first vocalization, latency of the approach to the speaker, time spent close the speaker (within 5 m), number of individuals that approached the speaker, and the number of vocalizations. We found that territorial White-eared Ground-sparrow pairs responded stronger to neighbors than non-neighbors, and this response is not influenced by duet duration or frequency characteristics. This result suggests that neighbors represent a greater territorial threat for White-eared Ground-sparrows than non-neighbors. Further work is necessary to understand how common this observation is for tropical species that defend small territories year-round.
Understanding speciation has long been a fundamental goal of evolutionary biology. It is widely accepted that speciation requires an interruption of gene flow to generate strong reproductive isolation between species. The mechanism of how speciation in sexually dichromatic species operates in the face of gene flow remains an open question. Two species in the genus Chrysolophus, the Golden Pheasant (C. pictus) and Lady Amherst's Pheasant (C. amherstiae), both of which exhibit significant plumage dichromatism, are currently parapatric in southwestern China with several hybrid recordings in field. In this study, we estimated the pattern of gene flow during the speciation of the two pheasants using the Approximate Bayesian Computation (ABC) method based on data from multiple genes. Using a newly assembled de novo genome of Lady Amherst's Pheasant and resequencing of widely distributed individuals, we reconstructed the demographic history of the two pheasants by the PSMC (pairwise sequentially Markovian coalescent) method. The results provide clear evidence that the gene flow between the two pheasants was consistent with the predictions of the isolation with migration model during divergence, indicating that there was long-term gene flow after the initial divergence (ca. 2.2 million years ago). The data further support the occurrence of secondary contact between the parapatric populations since around 30 kya with recurrent gene flow to the present, a pattern that may have been induced by the population expansion of the Golden Pheasant in the late Pleistocene. The results of the study support the scenario of speciation between the Golden Pheasant and Lady Amherst's Pheasant with cycles of mixing-isolation-mixing, possibly due to the dynamics of geographical context in the late Pleistocene. The two species provide a good research system as an evolutionary model for testing reinforcement selection in speciation.
Habitat transformation is identified as major threat to biodiversity loss globally, affecting threatened raptors. Changes in land use can alter the abundance and distribution of birds of prey by affecting habitat availability and quality. In this study, we used multivariate analyses to investigate the effect of habitat alteration on the demography of a declining Eastern Imperial Eagle (Aquila heliaca), making assumptions for future population trajectories. We used the Generalized Linear Mixed Models with Poisson distribution and Log link function, searching a relationship between the demographic parameters and the landscape structure and possible effects of fragmentation. In our study area, habitat change affected dramatically permanent grasslands, shrinking their availability. As we expected, the share of grasslands in eagles' territories significantly affected occupancy rate, but not productivity and breeding frequency. We found that occupancy rate decreased significantly, while productivity and breeding frequency showed no trend. Modeling the effect of habitat alteration on Eastern Imperial Eagle demography, we found out that territory quality was a more powerful factor driving the response of a top predator to the alteration of favorite foraging habitats. Only the habitat quality in source territories had a significant positive effect on eagle productivity. We found that simple rules to predict adverse agricultural impact on territory abandonment or breeding productivity of a top predator were not reliable. Our results could be used for planning conservation of other large territorial raptors, facing the same type of threat.
Many birds species breed in colonies. One of the species in the Corvidae family nesting in groups is the Rook (Corvus frugilegus). The construction of the nest is costly for birds and needs high energy expenditure. Therefore, birds should optimize the time of nest building in relation to environmental, especially weather, conditions. Furthermore, birds should adapt their breeding phenology, including the date of starting the construction of nests for climate change. We observed the dynamics of increasing numbers of nests in a colony of Rooks in relation to air temperature, wind, rainfall, snowfall and day-length (indirect indicator of photoperiodism). Observations were carried out during three breeding seasons (2015–2017) in a large rookery in a big city in north-eastern Poland. The increase in the number of nests was correlated only with day length and no effect of climatic factors on the number of nests in the colony was observed. Number of nests varied significantly between successive years of research. In the case of the Rook (predictable breeders), the photoperiod seems to be the most important factor influencing breeding behavior, especially nest construction. In the last three decades, increasing temperature and time of spring phases have advanced and have influenced changes in the phenology of the availability of food resources. Simultaneously, a rapid decline in the numbers of breeding pairs of the Rook in Poland has been observed, especially in the last three decades. Conservative attachment to the length of the day, which is the main factor responsible for the development of the breeding colony, makes the Rook appear to be a species with low plasticity in the face of rapid climate changes. Thus, we suggest that may indirectly influence the decrease in the breeding population of the Rook.
Generalist avian brood parasites vary considerably in their degree of host specialization (e.g., number of hosts); some parasitize the nests of just a few host species, whereas others exploit more than 100 species. Several factors, including habitat range, habitat type, and geographic location, have been suggested to account for these variations. However, inter-specific differences in individual attributes, such as personality and plasticity, have rarely been considered as potential factors of such variation, despite their potential relationship to, for example, range expansion. Using cage experiments, we tested the hypothesis that parasitic species exploiting more host species may be more active and exploratory. To this end, we quantified behaviors exhibited by two Cuculus cuckoos (Common Cuckoo C. canorus and Oriental Cuckoo C. optatus) that vary greatly in their number of host species. Specifically, we evaluated exploratory behavior displayed by birds in the cage, such as the number of movements, head-turning, wing-flapping, and stepping. The Common Cuckoo, which has a higher number of host species, tended to exhibit higher levels of exploratory behaviors than the Oriental Cuckoo. Our study showed that the two cuckoo species exhibited different exploratory levels, as predicted by the differences in their number of hosts. Further studies regarding the causality between individual attributes and host specialization with improved experimental methodology would greatly enhance our understanding of the role of individual characteristics in the coevolution of avian brood parasites and their hosts.
Knowledge of the higher-level phylogenetic relationships of birds has grown substantially during the past two decades due to the application of genomic data. However, the nomenclature of higher-level taxa has not become more stable, due to the lack of regulation of taxon names above the level of superfamily by the ICZN, and the usage of rank-based nomenclature, which is not tied to clades in a phylogeny. Lack of regulation and the instability of rank-based nomenclature impede effective communication among systematists. We review support for higher-level avian clades using a set of 10 phylogenomic data sets, and identify clades that are supported by congruency of at least four of these. We provide formal definitions of the names of these clades based on the rules of the recently published PhyloCode. The names of 25 clades are here defined using minimum-crown-clade (n = 23), minimum-clade (n = 1) and maximum-crown-clade (n = 1) definitions. Five new names are introduced here: Dinocrypturi, Pteroclimesites, Musophagotides, Phaethoquornithes and Pelecanes. We also review diagnostic apomorphies of the relevant clades, and identify known synonyms and homonyms. By establishing a formal link between higher-level taxon names and well-supported phylogenetic hypotheses, our phylogenetic definitions will provide a solid basis for the stabilization of avian higher-level nomenclature.
The avifauna in Tajikistan has been widely studied for the last century, but specific work on species richness pattern along elevation gradients in Tajikistan is rarely investigated. Here, we reported the first study of bird species richness (BSR) in the high-altitude mountain systems (Tien Shan and Pamir-Alay) of Tajikistan which are very sensitive to the recent climate changes. We aim to explore the relationship of BSR pattern with elevation gradient and to determine the potential drivers underlying the patterns. We collected occurrence data from field surveys, published articles, and open access websites to compile a list of bird species along elevational gradients across the whole country. The BSR was counted by 100 m elevational bands ranging from 294 m to 5146 m. The patterns of BSR were calculated separately for five groups: all breeding birds, Passeriformes, Non-Passeriformes, large elevational range species, and small elevational range species. We calculated ecological and climatic factors of planimetric area, mid-domain effect (MDE), habitat heterogeneity (HH), mean annual temperature (MAT), temperature annual range (TAR), annual precipitation (AP), normalized difference vegetation index (NDVI), human influence index (HII), and human disturbance (HD) in each elevational band. A combination of polynomial regression, Pearson's correlation, and general least squares model analyses were used to test the effects of these factors on the BSR. A unimodal distribution pattern with a peak at 750–1950 m was observed for all breeding birds. The similar pattern was explored for Passeriformes and Non-Passeriformes, while species with different elevational range sizes had different shapes and peak elevations. For all the breeding birds and Passeriformes, BSR was significantly related to spatial, climate and human influence factors, while BSR of Non-Passeriformes positively correlated with all the given factors. First, second and fourth range classes of birds were significantly correlated with human influence factors. Moreover, large-ranged species had positive correlations with the mid-domain effect and weakly with habitat heterogeneity. We found that area, MAT and AP were the main factors to explain the richness pattern of birds, and the species richness increases with these three factors increasing. Multiple factors such as area and climate explain 84% of the variation in richness. Bivariate and multiple regression analyses revealed a consistent influence of spatial and climate factors in shaping the richness pattern for nearly all bird groups.
Here we documented up-to-date information on breeding ecology of Buffy Laughingthrush (Garrulax berthemyi), an endemic species of China, and a sympatric coordinal Red-tailed Laughingthrush (Trochalopteron milnei), in southwestern China. Furthermore, we compared breeding ecology of these two sympatric species. No significant differences were found in clutch size, egg size, nest size, nest height, nest habitat and predation rate between these two species except nests depth, nests cover and eggs color. The Red-tailed Laughingthrush nestlings differed from those of the Buffy Laughingthrush in gape morphology and the extent of down. Observation of breeding behavior showed that cooperative breeding might exist in the population of Buffy Laughingthrush.
Birds have acute vision and many remarkable visual cognition abilities, due to their unique living environment. The underlying neural mechanisms have also attracted interests of researchers in neuroscience. Here, we firstly summarize the visual cognition abilities of birds, and make a comparison with mammals. Secondly, the underlying neural mechanisms are presented, including histological structure of avian brain and visual pathways, typical experimental results and conclusions in electrochemistry and electrophysiology. The latter mainly focuses on several higher brain areas related to visual cognition, including mesopallium ventrolaterale, entopallium, visual Wulst, and nidopallium caudolaterale. Finally, we make a conclusion and provide a suggestion about future studies on revealing the neural mechanisms of avian visual cognition. This review presents a detailed understanding of avian visual cognition and would be helpful in ornithology studies in the field of cognitive neuroscience.
Rear-edge populations of montane species are known to be vulnerable to environmental change, which could affect them by habitat reduction and isolation. Habitat requirements of two cold-adapted boreo-alpine owl species — Boreal Owl (Aegolius funereus) and Pygmy Owl (Glaucidium passerinum) — have been studied in refugial montane populations in the western Rhodopes, South Bulgaria. Data on owl presence and forest stand attributes recorded in situ have been used to identify significant predictors for owl occurrence. The results revealed Boreal Owl's preference for comparatively dense forests (high canopy closure values), big trees (diameter at breast height ≥50 cm) and large amount of fallen dead wood in penultimate stage of decay. For Pygmy Owl the only significant explanatory variable was the total amount of fallen dead wood. Results suggest preference of both owl species for forests with structural elements typical of old-growth forests (i.e., veteran trees, deadwood), the Pygmy Owl being less prone to inhabit managed forests. Being at the rear edge of their Palearctic breeding range in Europe both Boreal and Pygmy Owls are of high conservation value on the Balkan Peninsula. Hence, additional efforts are needed for their conservation in the light of climate change and resulting alteration of forest structural parameters. Current findings can be used for adjusting forest management practices in order to ensure both, sustainable profit from timber and continuous species survival.
The concept of foraging niche provides an insight into habitat use and dietary information of animals. Knowing intraspecific variation in foraging niche and trophic level is critical to the understanding of the species response to environmental changes during the process of range expansion, as well as the habitat management for conservation of threatened species. Using stable isotopic values of eggshell membranes (δ13C and δ15N), we examined whether there are differences in habitat use, trophic level, foraging niche width between the new and old breeding habitats (plains vs. mountains) of wild Crested Ibis (Nipponia nippon) in the early breeding season. Crested Ibis exhibited high variability in both δ13C and δ15N values, δ13C and δ15N varied as a function of habitat types. Birds breeding in plains had significantly higher δ13C but lower δ15N values compared to the birds breeding in mountains. Higher δ15N suggested that individuals in mountains consumed a great proportion of higher trophic level prey species in the early breeding season. Moreover, the isotopic niches were distinctly different in positions and showed small overlap between the two habitat types. The niche width was wider in old habitat than in the expanded new habitat. Our results demonstrated that the wild Crested Ibis had a high intraspecific variation in habitat uses and trophic levels in the early breeding season, and they could be divided into mountain and plain groups based on their different foraging niches. The difference in δ15N and niche width revealed that high trophic level food resources might be insufficient in plains. These findings stressed the importance of protecting foraging grounds in mountains and the necessity of improving foraging grounds in plains during winter and spring. Our study highlights the feasibility of investigating intraspecific variation in foraging ecology of birds through non-invasive isotopes of eggshell membranes. Understanding foraging niche variation gives us an insight into the food resource diversity in local areas and provides important information regarding particular foraging habitats that require protection.
Although Blakiston's Fish Owl (Bubo blakistoni) is widely treated as a single species, marked differences in the structure of pair duets between continental and insular populations have been documented. However, no study has quantitatively assessed these vocal differences. We obtained 192 duets from 22 pairs of Blakiston's Fish Owl: 15 pairs of B. b. blakistoni from the Japanese island of Hokkaido and the Russian Kuril island of Kunashir, and seven pairs of B. b. doerriesi from Primorye on the Russian mainland. This is a sizeable dataset for such a large, retiring, and rare owl. We conducted bioacoustic examinations of 14 vocal parameters using principal component analysis and the Isler criterion to quantitatively test species boundaries within the B. blakistoni complex. We found that the insular populations on Hokkaido and Kunashir emerged as vocally similar to each other but markedly different from the continental populations of B. blakistoni, corresponding closely with presently accepted subspecies limits. Bioacoustic differences in the duets of the insular and continental groups are greater than the pairwise comparisons of territorial vocalisations between other sympatric owl species. Based on the reproductive importance of vocal duets in owl biology, we propose the taxonomic elevation of the continental subspecies to species level as Northern Fish Owl B. doerriesi. Our study corroborates the importance of bioacoustics in ascertaining species boundaries in owls and has important implications for the management of the two newly delimited species, each likely to be assessed as Endangered. Both species should be managed independently to optimise conservation outcomes.
Urban ecosystems are evolutionarily recent novel environments acting as biodiversity filters. Psittacidae birds are considered successful urban adapters mainly due to their generalist feeding and opportunistic behavior, allowing them to occupy environments from cold temperate to dry xeric areas. Therefore, it is important to understand how these species interact in the urban environment. We studied the interannual (2013–2016) abundance of the White-fronted Parrot (Amazona albifrons) in the Neotropical cities of Xalapa and Coatepec, in Central Veracruz, México. Additionally, we studied the feeding ecology during 13 months of 6 parrot species detected in the city of Xalapa. The abundance of the White-fronted Parrot was significantly higher in Xalapa than in Coatepec, and it was homogeneous across years. Non-native plants represented 30–41% of Psittacidae diets in Xalapa, where seeds were the most commonly consumed resource. We recorded the highest Psittacidae species richness and highest diet overlap among species by the end of the dry season (April–May). The White-fronted Parrot had the highest plant richness in its diet, followed by the Monk Parakeet (Myiopsitta monachus) and the Green Parakeet (Psittacara holochlorus); yet, the White-fronted Parrot had a specialized diet dominated by two plant species (Grevillea robusta and Ficus aurea). The diet overlap among the three above-mentioned parrot species was not significantly different to a null model, where the White-fronted Parrot and the Monk Parakeet overlapped during the months of February, April, June, and September. The White-fronted Parrot is an urban adapter that has successfully expanded its geographic range via natural means and by human activities. The invasive Monk Parakeet is currently restricted to one park in Xalapa, and it has remained in that stage for many years (i.e., pre-expansion phase). Exotic plant species in Xalapa represent ∼55% of the woody vegetation, some of which have longer flowering and fruiting periods that may have aided the successful establishment of parrot species in urban environments.
The Chinese Egret (Egretta eulophotes) is a globally threatened bird species living on the coast and islands of Liaoning, northeastern China, mainly in summer. To further protect the breeding population of Chinese Egrets, it is important to understand the current protection status of their distribution sites at pre-migration period and migration routes. Thirty-three individuals were tagged with satellite transmitters at Fantuo Island in Changhai and Xingren Island in Zhuanghe, Liaoning Province, northeastern China, in July of 2016, 2017, and 2018, to identify important distribution sites during the pre-migration period, as well as detailed migration routes. The results showed that coastal mudflats in Liaoning and the west coast of North Korea were important feeding and roosting sites for fledgling Chinese Egrets from August to September. The home range sizes in August were significantly larger than in September. The eastern coast from Shandong to Guangdong, as well as Taiwan, China, and Manila Bay and Galileo Islands in the Philippines, were important stopover sites during fall migration. Specifically, we found that the egrets’ autumn migration could be divided into four routes, i.e., sea-crossing migration (SCM), coastal migration (CM), inland migration (IM), and mixed migration (MM). The migration distance, timing, speed, and straightness of the four routes also differed. The SCM routes were the straightest, and had the fastest migration speed and shortest travel time, while the IM routes had the lowest straightness and speed, and the longest duration. Manila Bay and Bohol Island in the Philippines, the west coast of Tanintharyi in Myanmar, and the Zengwun River Estuary in Taiwan, China, were wintering sites. Our findings on the key distribution sites along pre-migration and fall migration routes, including some stopover sites, have important implications for the conservation of and global action plan development for the vulnerable Chinese Egret.
The reproductive behaviors of birds are mainly controlled by the hypothalamus-pituitary-gonad axis. Many studies have shown that reproductive hormones are tightly linked to the breeding sub-stages. However, only a few studies have examined the temporal trend of hormone levels among different reproductive stages in multiple brooded species. We investigated the changes in plasma luteinizing hormone (LH) and prolactin (PRL) concentrations during different reproductive stages of the facultative double-brooded Great Tit (Parus major). We found that the concentrations of LH and PRL in females were significantly higher than those in males. Females had significantly higher LH and lower PRL concentrations in the pre-breeding period than in the first/second brooding periods, and there were no significant changes between the first and second brooding periods. The concentrations of LH and PRL in males had no significant difference between the pre-breeding period and the first brooding periods, while LH and PRL concentrations in the second brooding period were significantly higher than those in the first brooding period. We conclude that there are sex-based differences between LH and PRL at different stages of reproduction. The changes in LH and PRL in both males and females should be related to their physiological functions. Especially for males, individuals with higher levels of LH and PRL are more likely to maintain second clutches.
Egg discrimination by cavity-nesting birds that build nests under dim light conditions was presumed to depend on nest luminance, although this hypothesis has rarely been tested. Tests of egg discrimination ability by cavity-nesting tits under dim light conditions may reveal the selection pressure from brood parasitism that they encounter under natural interactions. We manipulated the intensity of luminance of nests of the Green-backed Tit (Parus monticolus), a potential cuckoo host that possesses a strong discrimination ability of non-mimetic foreign eggs. We performed experiments to test their egg discrimination ability under different light conditions. Our results showed that Green-backed Tits discriminate against non-mimetic foreign eggs under normal light conditions in nest boxes, and this ability persisted at nest luminance as low as 4.78 ± 1.31 lux that is several times lower than normal luminance (38.11 ± 24.02 lux). However, egg discrimination by Green-backed Tits disappeared when nest luminance was reduced to a minimum of 0.35 ± 0.15 lux. The latter value represents total darkness for humans. The present study shows that nest luminance plays a key role in egg discrimination by Green-backed Tits that build nests under dim light conditions. This study provides strong experimental evidence for nest illumination altering egg rejection behavior in cavity-nesting birds.
Knowledge of breeding success and its limiting factors is crucial in assessing species’ conservation needs. As cavity-nesters, parrots are particularly influenced by the availability of suitable cavities and low breeding output, whether due to natural processes or trapping. On the island of Sumba, Indonesia, the Critically Endangered Citron-crested Cockatoo (Cacatua citrinocristata) has the added problem of co-existing with an unusually rich hole-nesting bird community in a forested environment much constrained by habitat loss. We monitored 95 nesting cavities of cockatoos and their competitors and potential nest-predators, over one to four breeding seasons, using a combination of camera-traps, direct checks on nest contents, and observations from the ground. Competition for suitable cavities was intense among three large parrot species, two owls and a hornbill. Visitation rates by potential competitors were higher at unoccupied cavities than at those containing active nests, reflecting the guarding behaviour of the occupants. The Endangered Sumba Hornbill (Rhyticeros everetti) dominated observed direct confrontations and was the most frequent visitor to active parrot nests, suggesting a further role as a potential nest-predator. Cockatoos prospected many cavities but rarely then attempted to nest: instead the sites were usually occupied by other cavity-nesters, or by bees. At the few cavities where cockatoos did breed, predation pressure was likely low, and observed success rate high (10 successful of 15 nests), although the low number of nests found early in the breeding cycle suggests that some may have failed before detection. Intense competition for cavities suggests a shortage of suitable nest-sites, the need for preservation of old hole-bearing trees and a role for nestboxes. Accessible, known, safe artificial nest-sites would also provide opportunities to assess the scale of nest-site shortage, allow camera placements to study productivity, exclude some competitors and predators, and prevent illegal trapping. Especially given continued trapping pressure, the species would benefit from targeted local awareness-raising and law enforcement, with the whole endeavour backed up by longer-term forest restoration.
Sex differences in morphology provide key information for understanding a species' morphological adaptations in relation to the evolution of sexual selection. In migratory birds, morphological traits have adapted to long-distance travel, and sexual dimorphism is typically related to sex-differential migration phenology. Little Buntings (Emberiza pusilla) have one of the longest migrations and are the least dichromatic species among the Emberiza buntings. In this study, we measured sexual size dimorphism and sexual dichromatism of Little Buntings in relation to the spring arrival dates at a stopover site in Korea. Wing length was the most important predictor for identifying sex; the wings of males were longer than those of females. Males also had a significantly stronger chestnut color of the head feathers than females, but this color difference was more prominent in the spring than in the fall. Males arrived earlier than females by four days. Arrival dates correlated with both size and color, but unlike other bunting species previously studied in the same area, there was no clear sex-differential trend in the relationship between arrival date and morphological characteristics. Seasonal differences in the degree of sexual dichromatism suggest that chestnut plumage coloration can be used as a social or sexual signal of males in the breeding season. The correlation of size and color to early arrival regardless of sex may indicate that a preference for assortative mating exists or that a sex-differential migration strategy is not clearly defined in the early stages of northward migration. Our findings on the sexual dimorphism of Little Buntings provide insight into the evolution of the sex-differential migration of buntings in the East Asian Flyway.
Extreme hot weather is occurring more frequently due to global warming, posing a significant threat to species survival. Birds in particular are more likely to overheat in hot weather because they have a higher body temperature. This study used a heat stress model to investigate the antioxidant defense mechanisms and changes in fatty acid catabolism in Red-billed Leiothrix (Leiothrix lutea) to gain an understanding of how birds adapt to high temperatures. The birds were divided into five groups: a control group (30 ℃ for 0 days), 1 D group (40 ℃ for 1 day), 3 D group (40 ℃ for 3 days), 14 D group (40 ℃ for 14 days) and recovery group (40 ℃ for 14 days, then 30 ℃ for 14 days). Our results indicated that when Red-billed Leiothrix are subjected to heat stress, malondialdehyde (MDA) content in the liver significantly increased, as did the enzyme activities of catalase (CAT), glutathione–SH–peroxidase (GSH-PX) and total antioxidant capacity (T-AOC) in the liver. Furthermore, there was a significant increase in heat shock protein 70 (HSP70) expression in the liver, while avian uncoupling protein (avUCP) expression in muscle was significantly reduced. Additionally, there was a significant reduction in fatty acid catabolism enzyme activity such as 3-hydroxyacyl-CoAdehydrogenase (HOAD) activity in the heart, and carnitine palmitoyl transferase 1 (CPT-1) and citrate synthase (CS) activity in the heart and liver. Furthermore, fatty acid translocase (FAT/CD36) in the heart, heart-type fatty acid binding protein (H-FABP) and fatty acid binding protein (FABP-pm) in the liver and heart were also significantly decreased. These changes reverted after treatment, but not to the same level as the control group. Our results indicated that when Red-billed Leiothrix are exposed to heat stress their internal antioxidant defense system is activated to counteract the damage caused by high temperatures. However, even with high antioxidant levels, prolonged high temperature exposure still caused some degree of oxidative damage possibly requiring a longer recovery time. Additionally, Red-billed Leiothrix may be able to resist heat stress by reducing fatty acid transport and catabolism.
Conserving species relies upon acquiring an understanding of their use of habitat, yet our understanding of the use of habitat by co-existing species of different guilds at microgeographic scales remains poor. In particular, the use of habitat by woodland species is of conservation concern because of widespread declines in woodland biodiversity. Woodland bird declines have been ascribed, in part, to high deer densities because their browsing reduces the availability of nesting sites and food. We quantify the microgeographic use of habitat by Roe Deer (Capreolus capreolus) and of Great Tits (Parus major), Blue Tits (Cyanistes caeruleus) and Pied Flycatchers (Ficedula hypoleuca) in a heterogenous woodland landscape. We examined the use of habitat at microgeographic scales by the deer and the three bird species in relation to whether the local habitat was flat or wet or had a path, fence or wall within a 25-m radius of 206 randomly selected locations. We first examined if the occupancy rates of nestboxes in those locations were correlated with the number of Roe Deer lays and second, examined if the use of habitat by the Roe Deer and the bird species were associated with each of the habitat features that we quantified. We begin by showing that the use of habitat by Roe Deer is incongruent with the use of habitat by Great Tits, Blue Tits and Pied Flycatchers during the breeding season. Also, whilst all three bird species showed no, or weak, habitat preferences, the Roe Deer preferred daytime lay sites that were in flat areas of wet woodland close to paths, whilst there were no significant effects of the presence of fences and walls. These findings show that the Roe Deer and the three bird species differ in the use of habitat within a heterogenous woodland landscape, meaning that their use of habitat did not overlap at microgeographic scales. Meanwhile, the deer showed preferences for flat areas of wet woodland, whilst none of the bird species exhibited such preferences, and we discuss the implications of our findings for the management of woodlands.
Determining the migration routes and connections of migratory birds at the population level helps clarify intraspecific differences in migration. Five subspecies have been recognized in the Whimbrel (Numenius phaeopus) in Eurasia. Ssp. rogachevae is the most recently described subspecies. It breeds in Central Siberia, while its non-breeding region and migration routes are still unclear. We tracked the migration of Eurasian Whimbrels captured at three non-breeding sites (Moreton Bay in east coast of Australia, Roebuck Bay in Northwest Australia and Sungei Buloh Wetland in Singapore) and two migration stopover sites (Chongming Dongtan and Mai Po Wetland in China). We determined the breeding sites and inferred the subspecies of the tagged birds in the East Asian – Australasian Flyway (EAAF) based on the known breeding distribution of each subspecies. Of the 30 tagged birds, 6 and 21 birds bred in the breeding range of ssp. rogachevae and variegatus, respectively; one bred in the presumed transition area between the breeding range of ssp. phaeopus and rogachevae, and two bred in the region between the breeding range of ssp. rogachevae and variegatus. The birds that bred in the ssp. rogachevae breeding range spent their non-breeding season in the northern Sumatra, Singapore, East Java and Northwest Australia and mainly stopped over along China's coasts during migration. None of our birds bred in the exclusive breeding range of the phaeopus subspecies. Previous studies have predicted that rogachevae whimbrels migrate along the Central Asian Flyway and spend the non-breeding season in West India and East Africa. We found that at least some rogachevae whimbrels migrate along the EAAF and spend the non-breeding season in Southeast Asia and Australia. The ssp. phaeopus is at best sparsely distributed in the EAAF in the west region, or possibly does not occur at all.
The spatial distribution and breeding behavior of neighboring birds (conspecific and heterospecific) may influence reproduction and the effects differ across species. In this study, we investigated intra- and inter-specific spatial distribution of breeding via artificial nestboxes and examined whether overlap with neighbors affected reproductive success of the focal breeding pair. Regarding spatial distribution, Varied Tits (Sittiparus varius) and Cinereous Tits (Parus cinereus) showed similar pattern: distances of nestboxes containing conspecific tits were greater than those with heterospecific ones. In terms of breeding behavior, reproductive success was not significantly related to the distance from their neighbor’s nest. The reproductive success of Varied Tits was significantly related to that of their neighbors, while in Cinereous Tits, no strong link was found to any recorded reproductive behavior of the neighbors. These findings explain spatial variation in nest site selection of Varied Tits and Cinereous Tits. Reproductive success rate of Varied Tits is affected by that of the neighbors while that of Cinereous Tits is not. The results highlight that there are differences in reproductive outcome among related species and offer suggestions on the use of artificial nestboxes in experiment and conservation programs.
Global climate change has a significant effect on species, as environment conditions change, causing many species' distributions to shift. During the last three million years, the earth has experienced glacial oscillations, forcing some species to survive in ice-free refugia during glacial periods and then disperse postglacially. In this study, by assessing the potential distribution of Siberian Grouse (Falcipennis falcipennis), we used Global Circular Models and Representative Concentration Pathways to model their pattern of range changes during glacial oscillations and the potential impact of present global warming. We used 158 location records of Siberian Grouse to generate a full climate model using 19 bioclimate variables in MaxEnt. We discarded variables with a correlation coefficient larger than 0.8 and relatively lower modeling contributions between each pair of correlated variables. Using the remaining variables, we created a normally uncorrelated simple climate model to predict the possible distribution of Siberian Grouse from the most recent Ice Age to present and to 2070. Then we added geographical data and the human interference index to construct a multiple factor full model to evaluate which were important in explaining the distribution of Siberian Grouse. The Total Suitability Zone (P ≥ 0.33) of Siberian Grouse is about 243,000 km2 and the Maximum Suitability Zone (P ≥ 0.66) is 36,000 km2 and is confined to the Russian Far East. Potential habitat modeling suggested that annual precipitation, annual mean temperature, and the distance from lakes are the most explanatory variables for the current distribution of Siberian Grouse. The distribution center moved to the southeast during the Last Glacial Maximum and spread back to the northwest after the ice melted and temperatures rose. The total area range of Siberian Grouse experienced a dramatic loss during the Last Glacial Maximum. Global warming is presently forcing the Siberian Grouse to migrate northward with a contraction of its range. There is an urgent need to protect its habitat, because little of its Maximum Sustainable Zone is protected, although there are some large reserves in that area.
Species in Galliformes have elaborate ritual courtship displays, often including strutting, fluffing of tail or head feathers, and vocal sounds that serve as excellent examples of sexual selection. According to the male orientation to the female while either posturing or moving, these courtship displays of gallinaceous species can be classified into three categories: 1) ‘frontal displays’, 2) ‘lateral displays’, and 3) ‘both frontal and lateral displays’. Questions regarding which category of displays is the ancestral state and the evolutionary history of courtship displays in Galliformes remain unanswered. We collected and classified 131 species in terms of their courtship displays into the three categories listed above and carried out a large-scale comparative analysis to reveal the evolutionary trajectory of this trait. We found that the ancestral state of courtship displays of Galliformes involves both relatively short and straightforward frontal and lateral elements (i.e., the category of ‘both frontal and lateral displays’). Furthermore, ancestral trait reconstructions suggest that transitions from ‘lateral displays’ to ‘frontal displays’ occurred more frequently than the other way around (i.e., from ‘frontal displays’ to ‘lateral displays’). In addition, some transitions occurred from ‘both frontal and lateral displays’ to ‘lateral displays’ but not from ‘both frontal and lateral displays’ to ‘frontal displays’. Ancestral state reconstruction of courtship displays at the root of the Galliformes phylogeny supports the ‘both frontal and lateral displays’ first scenario. This original state then evolved towards two extremes, either ‘frontal displays’ or ‘lateral displays’, with more complicated and elaborate display components. Moreover, subsequent transitions occurred from ‘lateral displays’ to ‘frontal displays’ much more frequently than the other way around during the evolutionary history, indicating positive selection of ‘frontal displays’.
Conversion of natural environments to human-modified landscapes is continuing at an unprecedented rate, exerting fundamental influences on global biodiversity. Understanding how wildlife communities respond to landscape modifications is critical to improve biodiversity conservation in human-dominated landscapes. In this study, we surveyed bird communities in three common habitats (i.e., farmland, village, and forest) in the southern Anhui Mountainous Area during summer (August 2019) and winter (December 2020). The diversity metrics and species compositions of the avian communities were compared among the habitats, and the effects of land use composition in these habitats were tested. During the field surveys, we recorded 7599 birds of 120 species along 45 line transects of 1 km in length. The land use compositions differed among habitats, and land use diversity was the highest in villages and lowest in forests. The species richness and bird abundance in the two human-dominated habitats (i.e., farmland and village) were higher than those in forest in both seasons. Bird species composition also differed across habitat types in both seasons. Bird species feeding on vertebrates, fish and carrion, and species feeding on plants and seeds were mainly found in habitats with less construction lands and lower land use diversity, while omnivorous species and species feeding on fruits and nectar or on invertebrates were less affected by these two variables. The indicator species analysis showed that most species associated with forest feed on invertebrates, while species feeding on plants and seeds were more correlated with farmland and village. The results indicated that the conversion of natural habitats to human-dominated landscapes has pronounced impacts on bird communities in the study area. Human-dominated habitats harboured more avian species that deserve conservation attention. Meanwhile, bird conservations should not be relaxed in forests because there were more than 20 species that had a high specificity for forests.
Studies of biodiversity dynamics have been cast on either long (systematics) or short (ecology) time scales, leaving a gap in coverage for moderate time scales of decades to centuries. Large-scale biodiversity information resources now available offer opportunities to fill this gap for many parts of the world via detailed, quantitative comparisons of assemblage composition, particularly for regions without rich time series datasets. We explore the possibility that such changes in avifaunas across the United States and Canada before and after the first three decades of marked global change (i.e., prior to 1980 versus after 2010) can be reconstructed and characterized from existing primary biodiversity data. As an illustration of the potential of this methodology for sites even in regions not as well sampled as the United States and Canada, we also explored changes at a single site in Mexico (Chichén-Itzá). We analyzed two large-scale datasets: one summarizing bird records in the United States and Canada before 1980, and one for the same region after 2010. We used probabilistic inventory completeness analyses to identify sites that have avifaunas that have likely been inventoried more or less completely. We prepared detailed comparisons between the two time periods to analyze species showing distributional changes over the time period analyzed. We identified 139 sites on a 0.05° grid that were demonstrably well-inventoried before 1980 in the United States and Canada, of which 108 were also well-inventoried after 2010. Comparing presence/absence patterns between the two time periods for 601 bird species, we found significant spatial autocorrelation in overall avifaunal turnover (species gained and lost), but not in numbers of species lost. We noted potential northward retractions of ranges of several species with high-latitude (boreal) distributions, while other species showed dominant patterns of population loss, either rangewide (e.g., Tympanuchus cupido) or regionally (e.g., Thryomanes bewickii). We developed linear models to explore a suite of potential drivers of species loss at relatively fine-grained resolutions (<6 km), finding significant effects of precipitation increase, particularly on the eastern border of the United States and Canada. Our exploration of biotic change in Chichén-Itzá included 265 species and showed intriguing losses from the local avifauna (e.g., Patagioenas speciosa), as well as vagrant and recent invasive species in the Yucatán Peninsula. The present work documents both the potential for and the problems involved in an approach integrating primary biodiversity data across time periods. This method potentially allows researchers to assess intermediate-time-scale biodiversity dynamics that can reveal patterns of change in biodiversity-rich regions that lack extensive time-series information.