Clutch Size and Nest Survival of Cackling Geese in a Lesser Snow and Ross's Goose Colony

Abstract

Clutch size and nest survival of Cackling Geese (Branta hutchinsii hutchinsii) nesting among light geese (Lesser Snow Geese (Chen caerulescens) and Ross's Geese (C. rossii;)) were examined at Karrak Lake, Nunavut, in Canada's central arctic, 1999–2009. Islands of Karrak Lake and adjacent Adventure Lake were selected by Cackling Geese for nesting instead of mainland habitat. Cackling Geese increasingly nested on islands during the study, while light goose nesting declined. Clutch size varied by year (range: 3.4–4.4 eggs), and declined with nest initiation date ( NID = -0.l77 (95% CI:-0.228,–0.126)). Nest survival during incubation varied among years (range: 8.6–88.2%), and was lowest during early and late incubation, although 95% CI of slope estimates with nest age included zero ( Age = 0.156 (95% CI -0.072, 0.383), A2 = -0.006, (95% CI -0.027, 0.014)). Nest survival declined with individual nest initiation date ( NID = -0.431 (95% CI: -0.680, -0.182)). There was little support for nest survival models that included individual covariates of synchrony with light geese or weather during incubation. A posteriori analysis revealed that annual nest survival was greater in warmer years with less wind ( YearWeather = 1.738 (95% CI: 1.272, 2.205)), but spring phenology, intraspecific synchrony, or abundance of Cackling or light geese were not important. Reduced access to island-nesting geese by terrestrial predators, and predator satiation from high densities of nesting light geese on the surrounding mainland may result in islands within light goose colonies that are productive nesting habitats for many avian species, particularly if islands themselves are sparsely inhabited by light geese.