SEXUAL ROLES IN THE DOT-WINGED ANTWREN (MICRORHOPIAS QUIXENSIS), A TROPICAL FOREST PASSERINE

Dot-winged Antwrens maintain long-term pair bonds on year-long territories in tropical forests and woodland of Central and South America. Pairs partition breeding-related activities nearly equally. Like other antbirds (Formicariidae), both sexes incubate and brood. Both sexes participate equally in territorial maintenance behavior, which primarily involves active border displays. Initial investment in offspring is possibly equalized by long-term nuptial feeding of females by males. Overall, both sexes contribute equally to nestling care, although considerable variation is observed between nests, much of which probably results from variation in the foraging ability of parents. Females feed young consistently less often than do males during the early part of the nestling period and may be recovering from depletion of reserves resulting from egg production. In most pairs females bring more spiders than do males. This difference in prey type is unexpected, because the pair forages close together in the same microhabitat and their bill size is similar. Pairs are distinct in their interactions: some pairs have a rigid feeding order, and others do not

RUSSELL GREENBERG JUDY GRADWOHL, The Auk: Vol. 100, No. 4