LIFE-HISTORY CONSEQUENCES OF AVIAN BROOD REDUCTION

Studies of avian brood reduction characteristically focus on the short-term consequences of hatching asynchrony for offspring (e.g. number and sizes of fledglings), but a truly comprehensive brood-reduction theory needs to incorporate long-term fitness effects for parents if trimming family size leads to lessened parental effort thereafter. A simple model shows that a brood-reduction strategy is more likely to be favored by natural selection when early losses of one or more brood members in poor years (expedited by parental manipulation of hatching asynchrony) lead to significantly diminished parental work levels. Field workers should design experiments to assess the effects of brood reduction on parental work levels, parental survivorship, and/or future fecundity; they could do so simply by borrowing the experimental field techniques already employed in studies of avian reproductive costs.