1 see review by Powell 1985 and meta-analysis by Sridhar et al. Most research, however, has concentrated on flocks in forested systems, for which there are flock descriptions from all continents other than Antarctica (Fig. It occurs in many different kinds of ecosystems, including pelagic, wetland, and grassland systems, and in many different groups of birds including waterfowl, wading birds, and granivores (see review of Harrison and Whitehouse 2011). Mixed-species flocking of birds (hereafter referred to as “flocking”) is a well-studied, broadly distributed biological phenomenon. We then outline potentially fruitful future directions, focusing on studies that can investigate how dependent species are on each other in flocks, and how such interdependencies might affect avian habitat selection in the different types of human-modified environments of this region. We review the literature on flocks in East Asia and demonstrate there is a good foundation of knowledge on which to build.

Studies on how flocks respond to fragmentation and land-use intensification continue to accumulate, but the question of whether the flock phenomenon makes species more vulnerable to anthropogenic change remains unclear. We review from a community ecology perspective what is known about the structure and organization of flocks, emphasizing that flocking species tend to be those particularly vulnerable to predation, and flocks tend to be led by species that are able to act as sources of information about predators for other species. Mixed-species flocks of birds are distributed world-wide and can be especially dominant in temperate forests during the non-breeding season and in tropical rainforests year-round.

Bird flocks