Global patterns and predictors of bird species responses to forest fragmentation: Implications for ecosystem function and conservation

The fragmentation of forests is a dominant human impact worldwide with major implications for the conservation and management of ecosystems. Although many studies have assessed the effects of fragmentation on biodiversity at local scales, our understanding of the ecological implications for different functional groups of organisms remains limited, particularly at global scales. Here, we use linear mixed models to explore patterns of occurrence and ecological function of 2844 bird species at 293 localities spanning five continents. We show that sensitivity to fragmentation varies according to functional group and body mass, with the prevalence of insectivores and large frugivores declining in relation to fragment size, particularly under 100 ha. However, the most severe effects were restricted to the tropics, whereas fragmentation had no significant impact on the basic ecological structure of temperate bird communities. We conclude that land-use change in tropical systems is likely to disrupt biotic processes, including seed dispersal and the control of insect herbivores. Our findings highlight the importance of latitude in mediating the impacts of habitat loss, and offer general guidelines for the minimum size of fragments required to prevent the collapse of key ecosystem processes in sensitive regions.