ABSTRACT
Clearly insurance and developmental selection functions can be satisfied simultaneously.
Having established why parent birds often create surplus offspring, we now describe how parents (and offspring) go about eliminating offspring that are surplus to their needs {i.e. brood reduction). Avian brood reduction is usually the lethal outcome of sibling rivalry, although such behavior may serve parental interests, and may occur with or without the use of aggression among siblings (Lamey and Mock, 1991). Brood reduction is facilitated by establishing competitive asymmetries among the offspring prior to hatching via embryo asynchrony or differences in egg size or both, such that the last hatched chick is usually the first to succumb to selective starvation and/or siblicidal aggression.
