Is the White-flanked Antwren (Formicariidae: Myrmotherula axillaris) a nuclear species in mixed-species flocks? A field experiment
2002
Botero P, Carlos Andres
It has been suggested that the cohesion of mixed species flocks relies heavily on conspicuous species that act as an attractive nucleus for other birds. I evaluated the role of the White-flanked Antwren as a nuclear species in mixed-species flocks of gallery forests of eastern Colombia, and tested experimentally the hypothesis that the conspicuous wing-flashes of males contribute to interspecific cohesion. Although most of the species present in my study site showed a high propensity to flock heteroespecifically, interspecific associations of the White-flanked Antwren tended to be short. The white flanks of male White-flanked Antwrens were not critical for maintaining a particular number of species inside the flocks, for spacing out the individuals in the interspecific groups, or for prolonging the duration of the interspecific associations. The wing-flashes of the White-flanked Antwren provide an example of how assumptions about nuclear roles in species with conspicuous traits may lead to wrong conclusions about the dynamics of mixed-species flocking. My results suggest that although this antwren may be important for recruiting new members in forest flocks, it does not promote the maintenance of those associations.
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