Selfish begging by screaming cowbirds, a mimetic brood parasite of the bay-winged cowbird

Lichtenstein, G

G. Lichtenstein, Selfish begging by screaming cowbirds, a mimetic brood parasite of the bay-winged cowbird, ANIM BEHAV, 61, 2001, pp. 1151-1158

28

INGLESE

Article

Animal Sciences","Neurosciences & Behavoir

ANIMAL BEHAVIOUR

0003-3472 → ACNP

61

2001

6

1151 - 1158

ISI

0003-3472(200106)61:<1151:SBBSCA>2.0.ZU;2-H

Screaming cowbirds, Molothrus rufoaxillaris, are specialist parasites that almost exclusively parasitize bay-winged cowbirds, Molothrus badius. Parasi tic chicks are almost identical to the host young in their appearance and v ocalizations until the chicks attain nutritional independence. This system provides an excellent opportunity to study the relationship between begging behaviour and hunger level for parasitic chicks and host young. Using vide o analysis of laboratory experiments, I compared the begging behaviour of s creaming and bay-winged cowbird nestlings under controlled levels of food d eprivation with and without a nestmate. The results of these analyses indic ate that: (1) the begging behaviour of parasitic chicks and host young are influenced by their respective hunger levels; (2) the begging intensity of a cowbird chick is not influenced by the begging intensity of its nestmates ; and (3) parasitic chicks beg more intensely than host young for the same degree of hunger. The greater selfishness of the parasitic chicks is what w ould be expected from theory, because, unlike host chicks, their greed will not be constrained by kinship with their nestmates or with the host parent 's future broods. Alternative hypotheses explaining intense begging in term s of parasitic chicks being more hungry, or having to compensate for their alien appearance can be rejected, as the parasitic chicks and host young ar e similar in size and appearance. (C) 2001 The Association for the Study of Animal Behaviour.