Species and Sex-Differences in Hippocampus Size in Parasitic and Nonparasitic Cowbirds

JUAN C. REBOREDA; CLAYTON, NS; KACELNIK, A

NEUROREPORT

Año: 1996 vol. 7 p. 505 - 508

To test the hypothesis that selection for spatial abilities which require birds to locate, and return accurately to, host nests has produced an enlarged hippocampus in brood parasites, three species of cowbird were compared.  In shiny cowbirds, females search for host nests without the assistance of the male; in screaming cowbirds, males and females inspect hosts´ nests together; in bay-winged cowbirds, neither sex searches because this species is not a brood parasite.  As predicted, the two parasitic species had a relatively larger hippocampus than the non-parasitic one; and there were no sex differences in relative hippocampus size in screaming or bay-winged cowbirds, but in shiny cowbirds, the female had a larger hippocampus than the male.