A male Common Merganser. (Photo: Gregg Thompson)
A large water bird known as the Common Merganser is often mistaken for a loon, as Michael Stein reports in today’s BirdNote. That’s because they share many physical traits, but the merganser has one adaptation that gives it an edge in catching fish.
Common Mergansers Parallel Loons
CURWOOD: We’re up in the northlands with water and the birds that live on it for BirdNote® today. And as Michael Stein explains, sometimes birds are not what they seem.
[Common Merganser calling - file from Lang Elliott, musicofnature.com]
STEIN: On a northern lake surrounded by dense evergreens, a large water bird rests on the surface. Its long, slim body – more than two feet of it – appears mostly white, the back black, the head a deep green. And all of it glistens. The bird dives under, a graceful sliding motion. Then returns to the surface with a fish grasped firmly in its beak.The bird’s shape and behavior spell “loon.”
[Common Loon brief vocalization, http://macaulaylibrary.org/audio/43039, 0.35-.38]
But this is a male Common Merganser, a very large duck that hunts fish for a living.
[Common Merganser calling, http://macaulaylibrary.org/audio/61558, 0.14-.17]
The Common Merganser is one of our biggest ducks, about the size of some loons, or even a small goose. Although it’s not closely related to loons, it has evolved a similar overall structure and predatory behavior. But a merganser has a unique feature that a loon lacks: tooth-like serrations along the edge of the bill that help the bird grasp slippery fish.
Common Mergansers nest in the northern states and Canada. So do loons. But loons nest on the ground, while mergansers nest mostly in tree cavities and rock crevices. Cavities big enough to house a hefty 3½-pound female, plus about a dozen jumbo eggs. I’m Michael Stein.
Written by Bob Sundstrom
Common Merganser calls recorded by Lang Elliot, musicofnature.com. Common Loon brief vocalization, 43039 and 61558 recorded by William W. H. Gunn, provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York.
BirdNote’s theme music was composed and played by Nancy Rumbel and John Kessler.
Producer: John Kessler
Executive Producer: Sallie Bodie
© 2016 Tune In to Nature.org September 2016 Narrator: Michael Stein
CURWOOD: And for photos, paddle on over to our website, LOE.org.
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