Reproductive Effort and Breeding Success in Relation to Age by the Rook Corvus frugilegus

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Abstract
Young rooks should expend less energy in reproduction, per offspring produced, than old rooks. As a test of this hypothesis the time budgets were investigated of both males and females, the breeding pairs and the female in feeding the nestlings. Differences in the breeding ecology of old and young rooks were recorded. The results differed from the above mentioned theory. The parental effort of young birds is greater than that of older birds. During the incubation period, the young males fed their mates more frequently and were absent from the nest for longer periods than the older males. No differences were detected in the breeding behavior of old and young females, although those females mated to young males begged for food more frequently than did the females mated to old males. The young females also laid smaller clutches than the older females and were less successful in hatching out their eggs. The young males were less successful in rearing the nestlings than were the old males.