Brood parasitic cowbird nestlings use host young to procure resources.
Young brood parasites that tolerate the company of host offspring challenge the existing evolutionary view of family life. In theory, all parasitic nestlings should be ruthlessly self-interested and should kill host offspring soon after hatching. Yet many species allow host young to live, even though they are rivals for host resources. Here we show that the tolerance of host nestlings by the parasitic brown-headed cowbird Molothrus ater is adaptive. Host young procure the cowbird a higher provisioning rate, so it grows more rapidly. The cowbird's unexpected altruism toward host offspring simply promotes its selfish interests in exploiting host parents.
Department of Zoology, Downing Street, Cambridge CB2 3EJ, UK. rmk1002@hermes.cam.ac.uk
Rebecca M
RM
Kilner
Joah R
JR
Madden
Mark E
ME
Hauber
D000818:Animals; D001522:Behavior, Animal; D005247:Feeding Behavior; D005260:Female; D008297:Male; D009425:Nesting Behavior; D012044:Regression Analysis; D012919:Social Behavior; D020308:Songbirds / Q000254:growth & development / Q000502:physiology*