Hatching asynchrony, brood reduction and feeding patterns in tree swallows (Iridoprocne bicolor).

Abstract

A summary of Lack's (1954) brood reduction hypothesis for hatching asynchrony in birds is given. A recent objection to this hypothesis by Clark and Wilson (1981) is outlined. In an effort to better understand this controversy, the relationship between the degree of asynchrony and the frequency of brood reduction was explored using Tree Swallows (Iridoprocne bicolor). The results were inconclusive, probably because of the lack of food limitation during the season. Feeding patterns were also analyzed. It was observed that parents feed the nestling who's head is highest the majority of the time, but that often nestlings other than the highest are fed. Feedings were distributed to all different areas in the nest which is in sharp contrast to observations made in 1981. A feeding strategy based on behavioral changes with changing food availability is developed.