Common Mergansers are hardy, fish-eating, cavity-nesting ducks that can be found in New England year round, as they winter as far north as open water allows. However, the birds we see in the winter on large bodies of water most likely are not the same birds that breed here. All North American populations of Common Mergansers migrate, generally short to intermediate distances. Populations near the coast move only short distances, while more interior birds migrate farther. Heavier birds and adult males seem to tolerate colder winter temperatures and remain farther north than immature birds. They can often be seen on large lakes and rivers, as well as the coast, where they form small groups that may gather into large numbers at favored sites.
Migrating Common Mergansers tend to leave late in the fall (this week marks the peak of their fall migration), making them often the last waterfowl migrants to head south. Common Mergansers typically migrate over land at night, and along seacoasts or major river systems by day. In the spring, adult males return north first as soon as open water is available, followed by females a few weeks later. (Photo: 2 juvenile Common Mergansers) Thanks to canoe-steadying Sadie Richards for making it possible for me to take this photograph.
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