Factors influencing investigator-caused nest abandonment by North American dabbling ducks

Abstract

We examined factors (species, nest age, nest initiation date, clutch size, predator activity) that may affect the probability of investigator-caused nest abandonment in North American dabbling ducks and made predictions based on parental investment theory. For all nests, the best model contained species, nest stage, nest initiation date, and the interaction of species with nest initiation date. The probability of abandonment by Mallards ( Anas platyrhynchos L., 1758) was consistently higher than that of Blue-winged Teal ( Anas discors L., 1766). In these species, abandonment probability increased with later date, whereas Gadwall ( Anas strepera L., 1758), Northern Pintails ( Anas acuta L., 1758), and Northern Shovelers ( Anas clypeata L., 1758) showed the opposite pattern. Abandonment by all species declined as nest stage increased. Early-laying (≤5 eggs) females were 7 times more likely, and late-laying females were twice as likely, to abandon nests as incubating females. During incubation, abandonment probability was 38% higher during early (≤8 days) incubation than late incubation, and for each additional egg in a completed clutch, it was 19% lower. We propose a novel, two-stage model in which dabbling duck nest abandonment is influenced predominantly by opportunities for future reproduction during laying, and expected benefits from the current reproductive event during incubation.