Reproductive decisions by black brant: mechanisms to synchronize hatch and spatial variation in growth rates of goslings

Abstract

I investigated two aspects of reproductive decisions in Black Brant: synchronous hatch within clutches and areas in which to rear their broods. It has been hypothesized that Anatidae facilitate a synchronous hatch through vocalizations among embryos within the same clutch. I performed manipulative experiments in which variation was controlled for both genetic and incubation pattern sources in incubation period length. Our results suggest that vocalizations are not responsible for a synchronous hatch, and I suggest that inherent properties of the eggs themselves are responsible for a synchronous hatch. Additionally, I compared gosling growth rates from areas of low nest densities with those from a main colony to test the hypothesis that broods using dispersed areas were escaping density dependent effects. I found that goslings from dispersed nesting areas did not escape density dependent effects and may actually constitute a sink for the population from additional effects of increased nest mortality in dispersed nesting area.