Offspring begging and family conflict
The begging of the brood parasitic Brown-headed Cowbird (white rictal flanges) is more intense than its Dickcissel nestmates (yellow rictal flanges) when tested in the laboratory (top). This lone Brown-headed Cowbird in the nest of a Bell's Vireo (bottom) is unable to elicit the maximum rate of feeding from vireo foster parents and cowbirds grow at a slower rate than other species, suggesting the vireo may be a poor cowbird host.
Begging is part of a dynamic interaction between dependent offspring, who use begging to signal their need for a critical resource (typically food), and parents, who use begging signals to make decisions as to how much of that resource to provide. This dynamic interaction between parents and their offspring has garnered much interest from behavioral ecologists for its relevance to signaling theory and the study of parent-offspring conflict.

The bulk of my work in this area has focused on understanding the proximate and ultimate factors that influence the begging behavior of Brown-headed Cowbird nestlings. Because they are raised by unrelated host parents and typically compete against unrelated host nestmates (or less often, are raised alone), cowbirds are predicted to act more selfishly and beg more intensively than nonparasitic species to maximize their likelihood of survival in host nests. My work has investigated how nestmate size and short-term need influence begging behavior, the extent to which cowbird and host chicks differ in their begging, and whether cowbirds have evolved more exaggerated begging behavior than the nonparasitic, closely related Red-winged Blackbird (Agelaius phoeniceus).

Representative publications

Rivers, J. W., M. A. Blundell, T. M. Loughin, B. D. Peer, and S. I. Rothstein. 2013. The exaggerated begging behaviour of an obligate avian brood parasite is shared with a nonparasitic close relative. Animal Behaviour 86:xxx-xxx.

Rivers, J. W., T. M. Loughin, and S. I. Rothstein. 2010. Brown-headed Cowbird nestlings influence nestmate begging, but not parental feeding, in hosts of three distinct sizes. Animal Behaviour 79:106-117.

Rivers, J. W. 2009. Parent-absent begging in the Brown-headed Cowbird (Molothrus ater): the role of hunger and nestmate size. Behavioral Ecology and Sociobiology 63:707-717.

Rivers, J. W. 2007. Nestmate size, but not short-term need, influences the begging behavior of a generalist brood parasite. Behavioral Ecology 18:222-230.

Jim Rivers | Dept. Forest Ecosystems & Society, Oregon State University