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Abstract

A multiple regression analysis of current reproductive success (goslings fledged) on three male and female life-history traits (age, previous breeding periods, previous successes) was carried out for 31 semicaptive pairs of barheaded geese Anser indicus. Of the female variables, age proved positively and the number of previous nesting periods negatively related to current success. The latter relationship suggests that incubation has costs in terms of future fecundity for the female. Of the male variables, age was negatively and the number of previous fledging successes positively related to current reproductive success. Attempts with additional data to explain these findings in the male either by a positive feedback of success on future success or by differences in male quality gave inconclusive results, as did earlier attempts to demonstrate reproductive costs in geese and swans. In monogamous species with long-term pair bonds, where male and female share most of their life history but specialize in different activities, reproduction may affect the sexes in different ways. If the correlations between life-history traits of mates are not accounted for, individual strategies or constraints may be obscured by opposing effects in the mate.