Nest and mate choice in the red bishop (Euplectes orix):: female settlement rules

We investigated female settlement in a colony of red bishops (Euplectes orix), a territorial and highly polygynous weaverbird widely distributed over sub-Saharan Africa. An earlier study showed that male reproductive success is mainly determined by the number of nests a male builds in his territory, which appeared to be a good indicator of male quality. Because males provide no parental care or food resources within the territory, females sharing a territory do not compete for material resources and might therefore be expected to settle preferentially in territories of males that build many nests to gain the possible genetic benefit of high-quality offspring. An analysis of female settlement, however revealed that females did not show a preference for territories of males with many nests and that the distribution of female breeding attempts with regard to the number of vacant nests within a territory could be explained best by random female settlement in 3 out of 4 years. Females settled more often than expected by chance (in 3 out of 4 years) in territories already containing occupied nests, indicating that resident females did not discourage settlement of additional females. However, sharing a territory with other females might impose costs in terms of an increased predation risk because nests in territories that contained other nests with young suffered from higher predation than nests in territories that did not contain other nests with young. Females therefore might trade the possible benefits of settling in territories of males with many nests against the costs of sharing a territory with other females. This might result in the mating pattern found with random female settlement and male reproductive success being directly proportional to the number of nests built. We discuss possible implications of this mating pattern for sexual selection on males.