Distribution pattern and niche overlap of sympatric breeding birds along human-modified habitat gradients in Inner Mongolia, China

The transformation of natural habitats into human-modified landscapes has far-reaching consequences for species distribution and abundance. As species adapt to these changing environments, shifts in distribution patterns, niche dynamics, and interspecies interactions may occur, impacting biodiversity at multiple levels and potentially leading to ecosystem imbalances. This study aims to assess the impact of variations in vegetation composition and human disturbance on the distribution of sympatric breeding birds and to determine the extent of niche overlap or differentiation among these species. We conducted field surveys and collected data on bird distribution, vegetation composition, and level of human disturbance in eastern Inner Mongolian grasslands. We focused on the six most frequently co-occurring breeding birds, representing a mix of sparrows, larks, and corvids. Generalized Additive Models revealed varying responses of species occurrence along habitat gradients. Species like the Eurasian Skylark (Alauda arvensis), Mongolian Lark (Melanocorypha mongolica), and Asian Short-toed Lark (Calandrella cheleensis), increased in larger and more connected habitats, while others, like the Tree Sparrow (Passer montanus), Eurasian Magpie (Pica pica), and Barn Swallow (Hirundo rustica), adapted to more fragmented habitats. Niche analysis indicated habitat generalists tended to occupy larger niches than grassland specialists. Substantial niche overlap was also found among the six co-occurring bird species. Conservation efforts should consider the specific needs of specialist species and strive to maintain or restore critical grassland habitats. Additionally, promoting sustainable agricultural practices that balance the needs of birds and human activities can contribute to the coexistence of generalist and specialist bird species in modified landscapes.