Provisioning adjustments by male and female fairy martins to short-term manipulations of brood size

Abstract

In biparental birds, the relative contribution of the sexes to feeding their brood (provisioning share) is sometimes reported to vary with brood size. However, the explanation for changes in provisioning share are often ambiguous (particularly in correlational studies), while the variation in findings between studies remains poorly understood. In this study we examined how short-term, within-pair manipulations of brood size (reduced, original and enlarged) affected provisioning rate in the fairy martin, Hirundo ariel. Following each manipulation, provisioning rates were monitored continuously for a two day period. Total provisioning rate increased when broods were enlarged and decreased when..