Begging and short-term need in cowbird nestlings: how different are brood parasites?

LICHTENSTEIN, G Y D. DEARBORN

BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY

Springer

Lugar: Nueva York; Año: 2004 vol. 56 p. 352 - 359

0340-5443

Because brood parasitic nestlings are usuallyunrelated to their nestmates and to the provisioning adult,they are free from indirect costs of begging. Consequently,they are predicted to beg more intensely than host nestlings,and some models predict they will beg at an invariantlyhigh level, regardless of short-term need. Previouswork has shown intense begging by parasitic cowbirds,but short-term need was not controlled. In this study,we manipulated short-term need and measured beggingintensity in two species pairs of host and parasitic nestlings:shiny cowbirds (Molothrus bonariensis) parasitizinglarger hosts than themselves (rufous-bellied thrushes, Turdusrufiventris), and brown-headed cowbirds (M. ater)parasitizing smaller hosts than themselves (yellow warblers,Dendroica petechia). All four species increased theirbegging intensity with short-term need, though the changewas much less pronounced between food-deprived andcontrol treatments than between control and hand-feedingtreatments. Shiny cowbirds begged more intensely thanrufous-bellied thrushes following each treatment. In contrast,brown-headed cowbirds did not beg significantlymore intensely than yellow warblers under any of thetreatments.