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.

Biodiversity is declining at an unprecedented rate. Many grassland species have been lost and are now of conservation concern. Identifying efficient biodiversity indicators is a key pillar of the global conservation strategy. Mongolian Lark (Melanocorypha mongolica) is a charismatic bird species abound in Mongolian steppes, and recent studies demonstrated that this species share similar habitat requirements and likely co-occur with other grassland birds. We tested the hypothesis that Mongolian Lark would make a suitable indicator for different aspects of avian biodiversity. We made a large-scale bird survey in Inner Mongolia, and classified point counts into three groups based on different taxonomic, functional, and phylogenetic biodiversity measures. We identified species indicators of each group using the indicator value (IndVal) analysis, and examined the bird compositional difference among groups. Linear models were used for studying the patterns of occurrence of Mongolian Lark in relation to various biodiversity measures. Mongolian Lark showed the highest indicator value in comparison with other potential species indicators. Bird species richness is significantly higher at sites with Mongolian Lark, and its occurrence was negatively correlated with species abundance, functional richness, Rao's quadratic entropy and phylogenetic diversity. Mongolian Lark is therefore a suitable indicator species for avian biodiversity in Mongolian steppes. It is highly distinctive in flight and usually seen singly. The widespread distribution and charismatic appearance make it easy to monitor and adequate for citizen science, and may provide useful information on the paradigm of surrogacy in conservation ecology.