The Effect of Supplemental Food on Body Condition and the Timing of Reproduction in a Cooperative Breeder, the Florida Scrub-Jay

Abstract

I examined the importance of food availability on when or whether to breed in cooperatively breeding Florida Scrub-Jays (Aphelocoma coerulescens). Two of the major factors known to influence the timing of reproduction are adequate food for offspring and sufficient available food for breeding females to produce a clutch. If the nutritive needs of a breeding female affect the timing of clutch initiation, food supplemented females should lay before controls. Supplemented female breeders initiated clutches earlier and produced larger clutches than unsupplemented birds. If food abundance declines as the breeding season progresses to the point where fewer young can be fed, clutch size should also decline. Florida Scrub-Jay females laid smaller clutches as the season progressed. Additionally, female breeders given supplemental food had higher levels of body lipids than controls prior to clutch initiation. The food supplementation protocol also allows the testing of the hypothesis that nonbreeder Florida Scrub-Jays forgo breeding because they are food limited. If food limitation were the only factor in the 'decision' by nonbreeders to forgo breeding, individuals provided with food would become breeders at a higher frequency than unsupplemented birds. However, equal frequencies of control and supplemented nonbreeders became breeders. I also compared body mass and body lipid of breeders and nonbreeders and found that breeders were heavier and had higher percentages of body lipids than nonbreeders. However, these differences probably do not cause them to be nonbreeders but rather are a result of their being nonbreeders.