Risk-Taking by Incubating Common Goldeneyes and Hooded Mergansers

Abstract

We studied nest defense by Common Goldeneyes (Bucephala clangula) and Hooded Mergansers (Lophodytes cucullatus) nesting near Sudbury, Canada between 1989-1995. As incubation proceeded, female Common Goldeneyes took greater risks by allowing the observer to approach the nest more closely before flushing, landing closer to the nest after flushing, vocalizing more commonly when flushed, and giving more broken wing or distraction displays. Hooded Merganser females exhibited relatively strong defense at all stages, including giving distraction displays much earlier in incubation. An index of all four behaviors increased for each species as incubation proceeded. Nest defense by these cavity-nesting ducks differed from patterns known for ground-nesting waterfowl, perhaps due to effects of nest location, predation type and intensity, and nest parasitism. Future nest defense studies should consider the overall suite of behaviors that comprise parental strategies for defending their nests and/or offspring.