Barn Swallow Nest Predation by a Recent Urban Invader, the Taiwan Whistling Thrush - Implications for the Evolution of Urban Avian Communities.

Urban areas become a new habitat for an increasing number of species as they gradually adapt to the expanding, human-associated environment. The barn swallow (Hirundo rustica) has constructed nests on human buildings that provide good protection against bad weather and predators over centuries. In contrast, the Taiwan whistling thrush (Myophonus insularis) is one of new urban-invading species. The interactions between old and new urban avian species can determine the structure of this growing avian community. Here we report the first case of Taiwan whistling thrushes' predation on other birds in an urban area. Taiwan whistling thrushes were observed to eat all barn swallows' chicks and eggs on one street within one week and thus dramatically reduced their reproductive success, even severer than did a typhoon. The newly evolving predation behavior of Taiwan whistling thrushes could threaten the survival of barn swallows. If the latter cannot conquer the new challenge, the nesting ground may become an ecological trap to them driving population extirpation. This reported case implies that urbanization could intensify the interactions, such as predation or competition, between old and new urban species, leading to their population decline or growth and thus community dynamics of urban wildlife.