Dunlin (Calidris alpina) is a polymorphic species with a complex of subspecies. A migration stopover site on the intertidal mudflats of Jiangsu Province, China, has a pivotal role in the migratory connectivity of dunlin along the East Asian–Australasian Flyway (EAAF). However, to date, the dunlin subspecies that visit the coast of China during migration remains uncertain. To determine the subspecies, an integrated approach based on mitochondrial DNA, ring recoveries, and morphological traits was used to analyze dunlins sampled at the Jiangsu stopover site. Alaskan and Beringian lineages were the two dominant lineages that migrated through Jiangsu, and the number of dunlins from the Alaskan lineage greatly exceeded that from other lineages. According to genetic analysis, the proportion of identified lineages was greater than 70%. At least four subspecies were detected in eastern Jiangsu Province, including C. a. actites, C. a. kistchinski, C. a. sakhalina, and C. a. arcticola. There were significant differences in morphological characters between years, suggesting that proportions of subspecies at the stopover varied over time and that different subspecies adopted different migratory strategies and timings. The findings of this study highlight the need to further consider how subspecies contribute to the composition of populations and migratory connectivity of dunlin.

The biodiversity in mountainous ecosystems is high but is threatened by rapid environmental change. Urbanization and other anthropogenic factors in the mountains surrounding cities can affect land use and spatial fragmentation. Moreover, patterns of habitat are closely related to elevation and have a major effect on montane biodiversity. The aim of this study was to analyze the effects of spatial fragmentation on the vertical distribution pattern of bird diversity by characterizing the structure of the bird community, species diversity, and landscape factors at different altitudes. From 2016 to 2019, this study made a four-years continuous monitoring of the breeding biric belts. The result indicated Mount Tai harbored a high bird diversity. Bird richness, abundance and Shannon-Wiener index decreased with latitude in Mount Tai. Moreover, the composition of bird communities varied along altitudinal gradients and supported some special species in different elevational bands. Road density, number of habitat patches, patch density, and the percentage of forest significantly affected bird diversity. The effect of patch density was higher compared with other landscape factors. Sufficient habitat and more patches in the low-mountain belt supported higher bird diversity. The middle-mountain belt and high-mountain belt showed contrasting patterns. Our results highlight the effects of ongoing urbanization and human activities on montane biodiversity and emphasize the need for artificial habitats in the mountains surrounding cities to be managed.

The biodiversity in montane ecosystems is high but is threatened by rapid environmental change. Urbanization and other anthropogenic activities in the mountains surrounding cities can affect changes in land use and habitat heterogeneity. Moreover, patterns of habitat heterogeneity are closely related to elevation and have a major effect on montane biodiversity. The aim of this study was to analyze the effects of habitat heterogeneity on the vertical distribution pattern of bird diversity by characterizing the structure of the bird community, biodiversity, and landscape factors at different altitudes. Continuous monitoring of the breeding birds at Mount Tai from 2016 to 2019 revealed that forest reduced the diversity and abundance of birds and favored montane birds. Habitat composition varied at different altitudes. In the high-mountain belt and the middle-mountain belt, the habitat was primarily composed of forest. In contrast, artificial habitat was more common in the low-mountain belt. Bird abundance, species richness, and the Shannon-Wiener index decreased as the altitude increased, and the structure of the bird community significantly differed in the different belts. Some rare species tended to only occupy specific belts. Road density, number of habitat patches, patch density, and the percentage of forest significantly affected bird diversity. The effect of patch density was higher compared with other landscape factors. The “habitat amount hypothesis” was more suitable for explaining the elevational distribution pattern of bird diversity at Mount Tai. Sufficient habitat and more patches in the low-mountain belt supported higher bird diversity. The middle-mountain belt and high-mountain belt showed contrasting patterns. Our results highlight the effects of ongoing urbanization and human activities on montane biodiversity and emphasize the need for artificial habitats in the mountains surrounding cities to be managed.