Response to playback of nestling begging in the red-winged blackbird, Agelaius phoeniceus

Nestling birds may honestly signal their need for food to provisioning adults, or begging might be a manipulative attempt to coerce additional food from providers, but in either case, providers respond to an increase in begging with an increase in feeding. We used playback of begging calls recorded from nestlings to determine whether male and female red-winged blackbirds increase their feeding rates in response to an apparent increase in begging. Both females and males fed broods at significantly higher rates after 5-min begging call playbacks than before, although only eight of 30 males were observed to feed nestlings in this study. In contrast, using the same playback design, neither females nor males altered their feeding rates significantly in response to broadcasts of noise. These results and others suggest that begging vocalizations are a basis for short-term adjustments in the rate at which nestling birds are provisioned. These results are also compared with those of a similar study of the same species, in which playback had no significant effect on rates of provisioning. (C) 1998 The Association for the Study of Animal Behaviour.