Parent-Offspring Conflict over Independence in the Herring Gull (Larus argentatus)


Department of Biology and Preclinical Medicine, University of St. Andrews, St. Andrews, Fife, KY16 9TS, U.K.


Observations on 24 focal nests revealed that, at the time when parental investment in feeding fledging chicks declined, chicks showed a marked increase in begging, particularly in larger broods, whilst parents became less responsive to begging. That chicks suffer a cost from early termination of investment is indicated by the fact that third-hatched chicks, who had attempted (unsuccessfully) to initiate more feeds, were absent from the territory first, rather than the more mature first- and second-hatched chicks. Taken together, these results and related inter- and intra-brood contrasts in behaviour are interpreted as offering support for Trivers' theory of parent-offspring conflict over the termination of investment.