Nest Survival and Density of Cackling Geese (Branta Hutchinsii) Inside and Outside a Ross's Goose (<i>Chen Rossii</i>) Colony

Abstract

The influence of heterospecifics on successful avian reproduction remains poorly understood, despite the role that such relationships may play in the evolution of reproductive strategies. We estimated nest survival of Cackling Geese (Branta hutchinsii) near McConnell River, Nunavut, in 2004 and 2005 in relation to (1) nest initiation date; (2) nest age; (3) nesting habitat; (4) presence in or absence from a colony composed mainly of Ross's Geese (Chen rossii); and (5) density of neighboring Lesser Snow Geese (C. caerulescens caerulescens) and Ross's Geese. We also assessed whether there was any consistent pattern in nest densities of Cackling Geese inside and outside the colony, using distance sampling methods that account for imperfect detection. Nest survival declined both with later nesting and with increased densities of surrounding Lesser Snow Geese and Ross's Geese, independently of whether or not Cackling Geese nested in the Ross's Goose colony. However, despite these negative interspecific effects at the neighborhood scale, nests had higher survival probabilities inside the colony than outside it when we controlled for nest initiation date and density of neighboring Lesser Snow Goose and Ross's Goose nests. There was no consistent difference in nest densities of Cackling Geese nesting inside and outside the colony. We conclude that Cackling Geese coincidentally establish nest sites inside the colony; the best nest locations are in low-density areas of the colony, but the location of these areas is unpredictable among years because Ross's Geese usually initiate nests later than Cackling Geese.