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Positive Relationships between Association Strength and Phenotypic Similarity Characterize the Assembly of Mixed-Species Bird Flocks Worldwide

Sridhar, Hari and Srinivasan, Umesh and Askins, Robert A and Canales-Delgadillo, Julio Cesar and Chen, Chao-Chieh and Ewert, David N and Gale, George A and Goodale, Eben and Gram, Wendy K and Hart, Patrick J and Hobson, Keith A and Hutto, Richard L and Kotagama, Sarath W and Knowlton, Jessie L and Lee, Tien Ming and Munn, Charles A and Nimnuan, Somchai and Nizam, BZ and Peron, Guillaume and Robin, VV and Rodewald, Amanda D and Rodewald, Paul G and Thomson, Robert L and Trivedi, Pranav and Van Wilgenburg, Steven L and Shanker, Kartik (2012) Positive Relationships between Association Strength and Phenotypic Similarity Characterize the Assembly of Mixed-Species Bird Flocks Worldwide. In: AMERICAN NATURALIST, 180 (6). pp. 777-790.

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Official URL: http://dx.doi.org/10.1086/668012


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.

Item Type: Journal Article
Keywords: community assembly; interspecific competition; meta-analysis; mixed-species flocks; null models; positive interactions
Department/Centre: Division of Biological Sciences > Centre for Ecological Sciences
Date Deposited: 21 Dec 2012 04:00
Last Modified: 21 Dec 2012 04:00
URI: http://eprints.iisc.ac.in/id/eprint/45534

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