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China's coastal wetlands belong to some of the most threatened ecosystems worldwide. The loss and degradation of these wetlands seriously threaten waterbirds that depend on wetlands.
The China Coastal Waterbird Census was organized by volunteer birdwatchers in China's coastal region. Waterbirds were surveyed synchronously once every month at 14 sites, as well as irregularly at a further 18 sites, between September 2005 and December 2013.
A total of 75 species of waterbirds met the 1 % population level Ramsar listing criterion at least once at one site. The number of birds of the following species accounted for over 20 % of the total flyway populations at a single site: Mute Swan (Cygnus olor), Siberia Crane (Grus leucogeranus), Far Eastern Oystercatcher (Haematopus osculans), Bar-tailed Godwit (Limosa lapponica), Spotted Greenshank (Tringa guttifer), Great Knot (Calidris tenuirostris), Spoon-billed Sandpiper (Calidris pygmeus), Saunders's Gull (Larus saundersi), Relict Gull (Larus relictus), Great Cormorant (Phalacrocorax carbo), Eurasian Spoonbill (Platalea leucorodia), Black-faced Spoonbill (Platalea minor) and Dalmatian Pelican (Pelecanus crispus). A total of 26 sites supported at least one species of which their number met the 1 % criterion. Forty-two species met the 1 % criterion in the Yellow River Delta, Shandong; 29 at the Cangzhou coast, Hebei and 26 species at the Lianyungang coast, Jiangsu.
The results highlight the international importance of China's coastal wetlands for waterbirds. This study also demonstrates that participation of local birdwatchers in waterbird surveys results in data that are invaluable not only for understanding the current status of waterbirds in China's coastal regions but also for waterbird conservation and management.
Plastic waste and debris have caused substantial environmental pollution globally in the past decades, and they have been accumulated in hundreds of terrestrial and aquatic avian species. Birds are susceptible and vulnerable to external environments; therefore, they could be used to estimate the negative effects of environmental pollution. In this review, we summarize the effects of macroplastics, microplastics, and plastic-derived additives and plastic-absorbed chemicals on birds. First, macroplastics and microplastics accumulate in different tissues of various aquatic and terrestrial birds, suggesting that birds could suffer from the macroplastics and microplastics-associated contaminants in the aquatic and terrestrial environments. Second, the detrimental effects of macroplastics and microplastics, and their derived additives and absorbed chemicals on the individual survival, growth and development, reproductive output, and physiology, are summarized in different birds, as well as the known toxicological mechanisms of plastics in laboratory model mammals. Finally, we identify that human commensal birds, long-life-span birds, and model bird species could be utilized to different research objectives to evaluate plastic pollution burden and toxicological effects of chronic plastic exposure.
China is one of the countries with abundant waterbird diversity. Over the past decades, China’s waterbirds have suffered increasing threats from direct and indirect human activities. It is important to clarify the population trends of and threats to waterbirds as well as to put forward conservation recommendations.
We collected data of population trends of a total of 260 waterbird species in China from Wetlands International database. We calculated the number of species with increasing, declining, stable, and unknown trends. We collected threatened levels of waterbirds from the Red List of China’s Vertebrates (2016), which was compiled according to the IUCN criteria of threatened species. Based on literature review, we refined the major threats to the threatened waterbird species in China.
Of the total 260 waterbird species in China, 84 species (32.3%) exhibited declining, 35 species (13.5%) kept stable, and 16 species (6.2%) showed increasing trends. Population trends were unknown for 125 species (48.1%). There was no significant difference in population trends between the migratory (32.4% decline) and resident (31.8% decline) species or among waterbirds distributed exclusively along coasts (28.6% decline), inland (36.6% decline), and both coasts and inland (32.5% decline). A total of 38 species (15.1% of the total) were listed as threatened species and 27 species (10.8% of the total) Near Threatened species. Habitat loss was the major threat to waterbirds, with 32 of the total 38 (84.2%) threatened species being affected. In addition, 73.7% (28 species), 71.1% (27 species), and 57.9% (22 species) of the threatened species were affected by human disturbance, environmental pollution, and illegal hunting, respectively.
We propose recommendations for waterbird conservation, including (1) strengthening conservation of nature wetlands and restoration of degraded wetlands, (2) enhancing public awareness on waterbird conservation, (3) improving the enforcement of Wildlife Protection Law and cracking down on illegal hunting, (4) carrying out long-term waterbird surveys to clarify population dynamics, (5) restoring populations of highly-threatened species through artificial intervention, and (6) promoting international and regional exchanges and cooperation to share information in waterbirds and their conservation.
Habitat loss, fragmentation and decrease of habitat quality caused by urbanization have led to a dramatic decline in biodiversity worldwide. For highly urbanized areas, parks have become "islands" or habitat fragments for wildlife. As an important indicator group of urban ecosystem health, the response of birds to urbanization has attracted the global attention of ecologists. Understanding the key factors affecting bird diversity in urbanized environment is crucial to the protection of biodiversity in urban ecosystems.
We used the line-transect method to survey birds in 37 urban parks in Nanjing, China. We also measured a number of park characteristics (area, isolation, shape index, environmental noise, distance to city center, and habitat diversity) that are commonly assumed to influence bird diversity. We then used the information-theoretic multi-model inference approach to determine which park characteristics had significant impacts on bird species richness.
We found that park area, habitat diversity and the distance to city center were the best positive predictors of bird species richness in Nanjing urban parks. By contrast, park isolation, park shape and environmental noise had little or no influence on bird diversity.
Our study highlights the importance of park area, habitat diversity and the distance to city center in determining bird diversity in Nanjing city parks. Therefore, from a conservation viewpoint, we recommend that large parks with complex and diverse habitats far away from the city center should be retained or constructed to increase bird diversity in urban design and planning.
Introgression, the incorporation of genetic material from one (sub)species into the gene pool of another by means of hybridization and backcrossing, is a common phenomenon in birds and can provide important insights into the speciation process. In the last decade, the toolkit for studying introgression has expanded together with the development of molecular markers. In this review, we explore how genomic data, the most recent step in this methodological progress, impacts different aspects in the study of avian introgression. First, the detection of hybrids and backcrosses has improved dramatically. The most widely used software package is STRUCTURE. Phylogenetic discordance (i.e. different loci resulting in discordant gene trees) is another means for the detection of introgression, although it should be regarded as a starting point for further analyses, not as a definitive proof of introgression. Specifically, disentangling introgression from other biological processes, such as incomplete lineage sorting, remains a challenging endeavour, although new techniques, such as the D-statistic, are being developed. In addition, phylogenetics might require a shift from trees to networks. Second, the study of hybrid zones by means of geographical or genomic cline analysis has led to important insights into the complex interplay between hybridization and speciation. However, because each hybrid zone study is just a single snapshot of a complex and continuously changing interaction, hybrid zones should be studied across different temporal and/or spatial scales. A third powerful tool is the genome scan. The debate on which evolutionary processes underlie the genomic landscape is still ongoing, as is the question whether loci involved in reproductive isolation cluster together in 'islands of speciation' or whether they are scattered throughout the genome. Exploring genomic landscapes across the avian tree of life will be an exciting field for further research. Finally, the findings from these different methods should be incorporated into specific speciation scenarios, which can consequently be tested using a modelling approach. All in all, this genomic perspective on avian hybridization and speciation will further our understanding in evolution in general.
Barn Swallows (Hirundo rustica), a group of passerine birds comprised of six closely related subspecies, are well known throughout their nearly worldwide distribution, in part because of their close association with human settlements. A tractable species for both individual-based and population-level studies, Barn Swallows are a prominent model system in evolutionary, ecological, and behavioral research. Here we review work on sexual selection and population divergence in this species complex, focusing on comparative studies among populations and subspecies. We summarize variation in the targets of mate choice and in the information conveyed by sexually selected traits, and conclude that the benefits advertised by different traits may vary geographically. Finally, we consider the role of sexual selection as a driver of population divergence in this widespread and phenotypically variable species complex.
Mixed-species flocks of birds are distributed world-wide and can be especially dominant in temperate forests during the non-breeding season and in tropical rainforests year-round. We review from a community ecology perspective what is known about the structure and organization of flocks, emphasizing that flocking species tend to be those particularly vulnerable to predation, and flocks tend to be led by species that are able to act as sources of information about predators for other species. Studies on how flocks respond to fragmentation and land-use intensification continue to accumulate, but the question of whether the flock phenomenon makes species more vulnerable to anthropogenic change remains unclear. We review the literature on flocks in East Asia and demonstrate there is a good foundation of knowledge on which to build. We then outline potentially fruitful future directions, focusing on studies that can investigate how dependent species are on each other in flocks, and how such interdependencies might affect avian habitat selection in the different types of human-modified environments of this region.
Although the species-urban green area relationship (SARu) has been analyzed worldwide, the global consistency of its parameters, such as the fit and the slope of models, remains unexplored. Moreover, the SARu can be explained by 20 different models. Therefore, our objective was to evaluate which models provide a better explanation of SARus and, focusing on the power model, to evaluate the global heterogeneity in its fit and slope.
We tested the performance of multiple statistical models in accounting for the way in which species richness increases with area, and examined whether variability in model form was associated with various methodological and environmental factors. Focusing on the power model, we analyzed the global heterogeneity in the fit and slope of the models through a meta-analysis.
Among 20 analyzed models, the linear model provided the best fit to the most datasets, was the top ranked model according to our efficiency criterion, and was the top overall ranked model. The Kobayashi and power models were the second and third overall ranked models, respectively. The number of green areas and the minimum number of species within a green area were the only significant variables explaining the variation in model form and performance, accounting for less than 10% of the variation. Based on the power model, there was a consistent overall fit (r2 = 0.50) and positive slope of 0.20 for the species richness increase with area worldwide.
The good fit of the linear model to our SARu datasets contrasts with the non-linear SAR frequently found in true and non-urban habitat island systems; however, this finding may be a result of the small sample size of many SARu datasets. The overall power model slope of 0.20 suggests low levels of isolation among urban green patches, or alternatively that habitat specialist and area sensitive species have already been extirpated from urban green areas.
The ideal habitat use of waterbirds can be considered to be fixed, but current habitat use depends on environmental conditions, especially those of food characteristics, considered crucial to their use of habitats. Understanding how waterbirds respond to variation in food availability at degraded wetland sites and change their habitat use patterns over spatial and temporal scales should direct future conservation planning. The Objectives of this study were to identify these spatial-temporal foraging habitat use patterns of Hooded Cranes (Grus monacha) and their relationship with food characteristics in the severely degraded wetlands of the Shengjin and Caizi lakes along with the Yangtze River floodplain.
We investigated the changes in food characteristics, relative abundance and density of Hooded Cranes in various habitat types across three winter periods from November 2012 to April 2013. We examined the effect of these winter periods and habitat types on the pattern of use by the cranes and explored the relationship between these patterns and food characteristics using linear regression.
The food characteristics and habitat use clearly changed over spatial-temporal scales. In the early and mid-winter periods, the most abundant, accessible and frequented food resources were found in paddy fields, while in the late period the more abundant food were available in meadows, which then replaced the paddy fields. There were fewer effects of winter periods, habitat types and their interactions on habitat use patterns except for the effect of habitat types on the relative abundance, determined as a function of food abundance, but independent of food depth and sediment permeability.
In response to the degradation and loss of lake wetlands, the cranes shifted their habitat use patterns by making tradeoffs between food abundance and accessibility over spatial-temporal scales that facilitated their survival in the mosaic of these lake wetlands.
Restoration projects have been implemented worldwide to mitigate the adverse effects of the loss and degradation of wetland habitats. Much research has been carried out on the impacts on birds of wetland restoration and management projects in China. Studies have mainly investigated central or coastal wetlands, while inland wetlands in remote areas have been much less studied. We focused on examining the response of wild birds to wetland restoration in Dianchi Lake, south-west China.
The line transect method was performed at 26 sampling plots. Three of these were in the city, and to acquire all wild bird data 23 plots were located every 2-8 km along the shore of Dianchi Lake, between December 2011 and November 2013. We collected all related bird records by searching the available literature, articles, newspapers and records of birdwatchers to compare species variation before and after implementation of wetland restoration. To measure the relationships between waterbird assemblages and habitat structures, we used canonical correspondence analysis (CCA) to pair the main matrix of bird assemblages with a second matrix of habitat variables.
We recorded 182 bird species belonging to 51 families and 17 orders. Of the species, 42 were new records for Kunming City and 20 were new records for Yunnan Province. Ten waterbird species were found to have disappeared from the shore of Dianchi Lake. CCA results indicated that waterbirds could be divided into four categories based on their habitat preference: synanthropic (wintering gulls), special habitat (shorebirds), semi-natural (wintering coots and ducks) and disturbance-tolerant (resident) species.
Our study is the first to consider the entire wild bird community throughout the year and discuss the species variation before and after wetland restoration projects launched for Dianchi Lake. Distinct habitat requirements of different waterbird groups were detected in our study, suggesting different types of restoration and management should be implemented.
Gut microbiota play crucial roles in host health. Wild birds and domestic poultry often occupy sympatric habitats, which facilitate the mutual transmission of intestinal microbes. However, the distinct intestinal microbial communities between sympatric wild birds and poultry remain unknown. At present, the risk of interspecies transmission of pathogenic bacteria between wild and domestic host birds is also a research hotspot.
This study compared the intestinal bacterial communities of the overwintering Hooded Crane (Grus monacha) and the Domestic Goose (Anser anser domesticus) at Shengjin Lake, China, using Illumina high-throughput sequencing technology (Mi-Seq platform).
Our results revealed that Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes and Chloroflexi were the dominant bacterial phyla in both hosts. The gut bacterial community composition differed significantly between sympatric Hooded Cranes and Domestic Geese. However, the hosts exhibited little variation in gut bacterial alpha-diversity. The relative abundance of Firmicutes was significantly higher in the guts of the Hooded Cranes, while the relative abundances of Actinobacteria, Proteobacteria, Bacteroidete and Chloroflexi were significantly higher in guts of Domestic Geese. Moreover, a total of 132 potential pathogenic operational taxonomic units (OTUs) were detected in guts of Hooded Cranes and Domestic Geese, and 13 pathogenic OTUs (9.8%) were found in both host guts. Pathogenic bacterial community composition and diversity differed significantly between hosts.
The results showed that the gut bacterial community composition differs significantly between sympatric Hooded Cranes and Domestic Geese. In addition, potential pathogens were detected in the guts of both Hooded Cranes and Domestic Geese, with 13 pathogenic OTUs overlapping between the two hosts, suggesting that more attention should be paid to wild birds and poultry that might increase the risk of disease transmission in conspecifics and other mixed species.
Resemblance to raptors such as hawks (Accipiter spp.) is considered to be an adaptive strategy of cuckoos (Cuculus spp.), which has evolved to protect cuckoos against host attacks. However, the effectiveness of the mimicry remains controversial, and is not yet fully studied for highly aggressive hosts.
We evaluated the effectiveness of sparrowhawk (Accipiter nisus) mimicry by common cuckoos (Cuculus canorus) in oriental reed warblers (Acrocephaus orientalis), which are highly aggressive hosts. Using a both the single and the paired dummy experiment, defense behaviors and attack intensities of oriental reed warblers against common cuckoos, sparrowhawks and oriental turtle doves (Streptopelia orientalis) were assessed.
Oriental reed warblers exhibit strong nest defense behaviors, and such behaviors do not change with breeding stage (i.e., egg stage and nestling stage). Furthermore, assistance from conspecific helpers may increase attack intensities. However, they were deterred from mobbing overall by the presence of the hawk.
Oriental reed warblers are able to distinguish cuckoos from harmless doves. However, they may be deterred from mobbing by the presence of the predatory hawk, suggesting hawk mimicry may be ineffective and does not reduce attacks of cuckoos by highly aggressive hosts.
Migration theory suggests, and some empirical studies show, that in order to compete for the best breeding sites and increase reproductive success, long-distance avian migrants tend to adopt a time minimization strategy during spring migration, resulting in shorter duration spring migration compared to that in autumn.
Using GPS/GSM transmitters, we tracked the full migrations of 11 Greater White-fronted Geese (Anser albifrons) between southeast China and the Russian Arctic, to reveal the migration timing and routes of the East Asian population, and compare the difference in duration between spring and autumn migration of this population.
We found that migration in spring (79±12 days) took more than twice as long to cover the same distance as in autumn (35±7 days). This difference in migration duration was mainly determined by significantly more time spent in spring (59±16 days) than in autumn (23±6 days) at significantly more stopover sites.
We suggest that these geese, thought to be partial capital breeders, spent almost three quarters of total migration time at spring stopover sites to acquire energy stores for ultimate investment in reproduction, although we cannot reject the hypothesis that timing of the spring thaw also contributed to stopover duration. In autumn, they acquired necessary energy stores on the breeding grounds sufficient to reach Northeast China staging areas almost without stop, which reduced stopover times in autumn and resulted in the faster autumn migration than spring.
Zoo and wildlife management faces a problem with bird sexing,as many bird taxa have indiscernible gender differences in size and coloration. Problematic groups are geese,cranes,rails,raptors,owls,parrots,doves,auks,shearwaters and some passerines. Commonly accepted invasive sexing techniques based on genetics,laparoscopy,morphometric and on cloacal inspection,are all needed in bird capturing and handling. Capturing and subsequent manipulations may be inapplicable for free-ranging birds,whereas distant voice-based sexing is relevant for many species. This review evaluates the potential for noninvasive sexing by separate calls or duet calls,for adult birds of 69 species from 16 orders and for chicks of 11 species from 7 orders. For adult birds of 25 species,a single call per individual was sufficient for 100 % reliable sexing by ear or using spectrographic analysis. For chicks,the potential for voice-based sexing seems to be very limited. For birds calling rarely or unpredictably,we propose a simple way of provoking vocalization using playbacks of species-specific calls that are available from sound libraries. We conclude that sexing by voice may represent a feasible alternative to the classical sexing techniques,both in the wild and in captivity.
Hybridization is not always limited to two species; often multiple species are interbreeding. In birds, there are numerous examples of species that hybridize with multiple other species. The advent of genomic data provides the opportunity to investigate the ecological and evolutionary consequences of multispecies hybridization. The interactions between several hybridizing species can be depicted as a network in which the interacting species are connected by edges. Such hybrid networks can be used to identify 'hub-species' that interbreed with multiple other species. Avian examples of such 'hub-species' are Common Pheasant (Phasianus colchicus), Mallard (Anas platyrhynchos) and European Herring Gull (Larus argentatus). These networks might lead to the formulation of hypotheses, such as which connections are most likely conducive to interspecific gene flow (i.e. introgression). Hybridization does not necessarily result in introgression. Numerous statistical tests are available to infer interspecific gene flow from genetic data and the majority of these tests can be applied in a multispecies setting. Specifically, model-based approaches and phylogenetic networks are promising in the detection and characterization of multispecies introgression. It remains to be determined how common multispecies introgression in birds is and how often this process fuels adaptive changes. Moreover, the impact of multispecies hybridization on the build-up of reproductive isolation and the architecture of genomic landscapes remains elusive. For example, introgression between certain species might contribute to increased divergence and reproductive isolation between those species and other related species. In the end, a multispecies perspective on hybridization in combination with network approaches will lead to important insights into the history of life on this planet.
The banning of fisheries discards by imposing an obligation to land unwanted catch constitutes a key point of the Common Fishery Policy reform proposed by the European Commission. The effect of such a ban on discards on top marine predators such as seabirds is largely unknown, especially in oligotrophic systems of the Mediterranean. The current study investigates the presence of scavenging seabirds around fishing trawlers as well as the exploitation of discards produced by bottom trawlers in the eastern Ionian Sea.
On-board observations were randomly conducted in May and December 2014, in order to record the presence and use of fishery discards by two common seabird species, namely, Scopoli's Shearwater (Calonectris diomedea) and the Yellow-legged Gull (Larus michahellis).
A total of 3400 seabirds were counted during May of which 2190 individuals were Scopoli's Shearwaters and 1210 were Yellow-legged Gulls. The latter species was the only scavenger observed during winter and in total, 768 individuals were counted. Differences in species abundance in the study area are related to breeding phenology and migratory movements. The number of seabirds attending bottom trawler operations during morning and afternoon hours showed no significant differences for both seabird species. Both scavenging seabirds extensively exploited fishery discards, which were mainly demersal fish, and consumed 70–80% of the total fishery discards biomass; however, they appeared to avoid poisonous species and/or large-sized fish. Yellow-legged Gulls displayed kleptoparasitic behaviour on Scopoli's Shearwater during feeding experiments. The number of such incidents depended on the number of gulls around the fishing vessel, with more than 90% success rates.
Considering the average annual biomass of discards estimations and the consumption rate found in this work, 106.1–117.9 t may be offered as a food subsidy to scavenging seabirds in the study area and should support a substantial part of local populations. Our results constitute baseline information on the annual amount of fishery discards and their exploitation rate by seabirds in the Ionian Sea, and suggest further work for a complete understanding of the potential impacts of the discards reform bill on seabirds.
Edge effects cause changes in bird community richness, abundance, and/or distribution within a landscape, but the avian guilds most influenced can vary among regions. Although Southeast Asia has the highest rates of deforestation and projected species loss, and is currently undergoing an explosive growth in road infrastructure, there have been few studies of the effects of forest edges on avian communities in this region.
We examined avian community structure in a dry evergreen forest in northeastern Thailand adjacent to a five-lane highway. We evaluated the richness and abundance of birds in 11 guilds at 24 survey points on three parallel transects perpendicular to the edge. At each point, 10-min surveys were conducted during February?August 2014 and March?August 2015. Vegetation measurements were conducted at 16 of the bird survey points and ambient noise was measured at all 24 survey points.
We found a strongly negative response to the forest edge for bark-gleaning, sallying, terrestrial, and understory insectivores and a weakly negative response for arboreal frugivore-insectivores, foliage gleaning insectivores, and raptors. Densities of trees and the percentage canopy cover were higher in the interior, and the ambient noise was lower. In contrast, arboreal nectarivore-insectivores responded positively to the forest edge, where there was a higher vegetation cover in the ground layer, a lower tree density, and a higher level of ambient noise.
Planners should avoid road development in forests of high conservation value to reduce impacts on biodiversity. Where avoidance is impossible, a number of potential mitigation Methods are available, but more detailed assessments of these are needed before they are applied in this region.
Animals that live at higher latitudes/elevations would have a larger body size (Bergmannos rule) and a smaller appendage size (Allenos rule) for thermoregulatory reasons. According to the heat conservation hypothesis, large body size and small appendage size help animals retain heat in the cold, while small body size and large appendage size help them dissipate heat in the warm. For animals living in seasonal climates, the need for conserving heat in the winter may tradeoff with the need for dissipating heat in the summer. In this study, we tested Bergmannos rule and Allenos rule in two widely-distributed passerine birds, the Oriental Magpie (Pica serica) and the Oriental Tit (Parus minor), across geographic and climatic gradients in China.
We measured body size (body mass and wing length) and appendage size (bill length and tarsus length) of 165 Oriental Magpie and 410 Oriental Tit individuals collected from Chinese mainland. We used linear mixed-effect models to assess variation patterns of body size and appendage size along geographic and climatic gradients.
Oriental Magpies have a larger appendage size and Oriental Tits have a smaller body size in warmer environments. Appendage size in Oriental Magpies and body size in Oriental Tits of both sexes were more closely related to the climates in winter than in summer. Minimum temperature of coldest month is the most important factor related to bill length and tarsus length of male Oriental Magpies, and wing length of male and female Oriental Tits. Bill length and tarsus length in female Oriental Magpies were related to the annual mean temperature and mean temperature of coldest quarter, respectively.
In this study, Oriental Magpies and Oriental Tits followed Allenos rule and Bergmanno rule respectively. Temperatures in the winter, rather than temperatures in the summer, drove morphological measurements in Oriental Magpies and Oriental Tits in Chinese mainland, demonstrating that the morphological measurements reflect selection for heat conservation rather than for heat dissipation.
Among urban stimuli, anthropogenic noise has been identified to be one of the behavioral drivers of species that rely on acoustic signals for communication. Studies have shown both species-specific and assemblage responses to urban noise, ranging from the modulation of their acoustic frequencies and spatiotemporal adjustments to declines in species richness. In this study, we assessed the citywide relationship between two anthropogenic noise variables (noise levels recorded during bird surveys and daily average noise levels) and vegetation cover with bird species richness.
This study was conducted in the city of Xalapa (Mexico) through a 114 citywide point-count survey. We recorded bird communities at each sampling site. We measured noise levels using a sound level meter while performing point-counts. Then, we generated a map of average daily noise of the city using an array of 61 autonomous recording units distributed across the city of Xalapa and calculated daily noise levels for the 114 points. We ran a linear model (LM) to assess potential relationships between both point-count and daily (24 h) noise values and vegetation cover with bird richness.
Results from the LM show: (1) a negative relationship between maximum point-count noise and avian species richness, (2) no relationship between 24 h noise and bird species richness, and (3) a positive relationship between vegetation cover and bird species richness.
Results provide evidence that decreases in urban bird species richness do not necessarily imply the permanent absence of species, suggesting that birds can temporarily fly away from or avoid sites when noisy, become cryptic while noisy events are occurring, or be undetected due to our inability to record them in the field during noisy events.
Urbanisation is a dominant geographical trend and an important component of global change, with unprecedented implications for socio-economic, cultural and environmental characteristics. However, green areas, including original fragments, can help to conserve native diversity, improving the functioning of these artificial systems in the long term. Urban areas can still provide habitats usable by wild birds, however the structural characteristics of the habitat formed by different types of green area differ, and therefore dissimilar bird diversities are to be expected. The object of this study was to characterise the α and β diversities of birds in different green areas and to analyse how diversity relates to ten variables that characterise the habitat.
We studied the green areas in the city of Temuco, southern Chile (Park, Square and Median strips of main streets), evaluating the variables: (a) surface area, (b) vegetation, (c) estimated human impact as the proportions of vegetation and bare soil by area, and the vehicle traffic. The bird assemblage structures were characterised by α (intra-environment) diversity and β diversity (between environments) and the statistical analysis identified the environmental variables related with the presence and abundance of birds. A statistical model was constructed to describe the contribution of the variables to bird diversity.
We found significant differences between the diversity of bird species in the three types of green area. The β showed medium to high similarity between the different study units. There was a negative correlation with bare soil areas; the correlations with vehicle flow, plant structure and tree and shrub cover were not significant, meaning that these variables did not explain the variation in the richness of bird species between the green areas. However the surface area did explain this variation presenting a positive potential relation. There was also a high correlation with the origin (native) of shrub species.
The bird diversity varied significantly according to the type of urban green area. The environmental variables presenting significant correlations with bird diversity were: surface area, native species of shrub stratum, shrub cover, and bare soil area. The best multiple regression model showed that the three most important variables for bird diversity are the surface area of the green area, the cover of the shrub stratum and the presence of native shrub species.
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