Positive relationships between association strength and phenotypic similarity characterize the assembly of mixed-species bird flocks worldwide

Competition theory predicts that local communities should consist of species that are more dissimilar than expected by chance. We find a strikingly different pattern in a multicontinent data set (55 presence-absence matrices from 24 locations) on the composition of mixed-species bird flocks, which are important sub-units of local bird communities the world over. By using null models and randomization tests followed by meta-analysis, we find the association strengths of species in flocks to be strongly related to similarity in body size and foraging behavior and higher for congeneric compared with noncongeneric species pairs. Given the local spatial scales of our individual analyses, differences in the habitat preferences of species are unlikely to have caused these association patterns; the patterns observed are most likely the outcome of species interactions. Extending group-living and social-information-use theory to a heterospecific context, we discuss potential behavioral mechanisms that lead to positive interactions among similar species in flocks, as well as ways in which competition costs are reduced. Our findings highlight the need to consider positive interactions along with competition when seeking to explain community assembly

Some Observations on the Geographic Variation of Mixed species Bird Flocks in Sri Lanka

Volume: 104Start Page: 96End Page: 9

Status of White headed Or Australian Stilt Himantopus Leucocephalus in Sri Lanka

Volume: 106Start Page: 98End Page: 9

The seasonality of mixed-species bird flocks in a Sri Lankan rainforest in relation to the breeding of the nuclear species, Orange-billed Babbler Turdoides rufescens

Volume: 29Start Page: 138End Page: 13