Bird guild loss and its determinants on subtropical land-bridge islands, China

Background The guild concept is useful for understanding the community structure in a land-bridge island system, but most fragmentation studies have focused only on the importance of island area and isolation, other island attributes such as perimeter-area ratio (PAR) were overlooked or understudied.

Methods We have adopted a guild approach to investigate the impacts of island attributes on bird guild richness on a set of 41 recently isolated land-bridge islands in the Thousand Island Lake (TIL), China.

Results We found insectivores had the largest number of species (34 species), followed by understory foraging guilds (28 species), omnivores (27 species) and canopy guilds (25 species). Furthermore, our data showed that migrants and residents responded equally to island area, insectivores and understory guilds were sensitive to island area but omnivores and canopy guilds were not very sensitive. Most guild richness was determined by island area, except for omnivores and canopy guilds.

Conclusions Although PAR or habitat diversity found to be important for bird species richness, our results highlight the importance of island area in maintaining bird diversity in fragmented island systems.