Nesting habits of Hooded Mergansers Mergus cucullatus in northeastern Ontario

Abstract

We studied the nesting habits of Hooded Mergansers in northeastern Ontario. Twelve females exhibited vigorous nest defence from early incubation onwards; seven incubating females spent 85.3% of their day on the nest, taking an average of 4.7 recesses each day, each with an average duration of 60 minutes. They lost up to 16% body mass during incubation. Our results confirm earlier studies which suggested that interspecific nest parasitism is a common feature of Hooded Mergansers nesting biology.