Health & Environmental Research Online (HERO)


Print Feedback Export to File
524044 
Journal Article 
Why do birds participate in mixed-species foraging flocks? A large-scale synthesis 
Sridhar, H; Beauchamp, G; Shanker, K 
2009 
Yes 
Animal Behaviour
ISSN: 0003-3472
EISSN: 1095-8282 
78 
2 
337-347 
English 
Mixed-species flocks of foraging birds have been documented from terrestrial habitats all over the world and are thought to form for either improved feeding efficiency or better protection from predators. Two kinds of flock participants are recognized: those that join other species ('followers') and are therefore likely to be the recipients of the benefits of flock participation and those that are joined ('leaders'). Through comparative analyses, using a large sample of flocks from around the world, we show that (1) 'followers' tend to be smaller, more insectivorous, and feed in higher strata than matched species that participate in flocks to a lesser extent and (2) 'leaders' tend to be cooperative breeders more often than matched species that are not known to lead flocks. Furthermore, meta-analyses of published results from across the world showed that bird species in terrestrial mixed-species flocks increase foraging rates and reduce vigilance compared to when they are solitary or in conspecific groups. Moreover, the increase in foraging rates is seen only with flock followers and not flock leaders. These findings suggest a role for predation in the evolution of mixed-species flocking. Species that are vulnerable to predation follow species whose vigilance they can exploit. By doing so, they are able to reduce their own vigilance and forage at higher rates. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. 
antipredator vigilance; foraging; leadership; meta-analysis; mixed-species flock; pairwise comparative method; typical antbirds thamnophilidae; rain-forest; phylogenetic-relationships; deciduous woodland; predator avoidance; neotropical birds; field experiment; passerine birds; feeding flocks; selfish herd