Wednesday, December 8, 2010

Common Merganser

On Tuesday, 7 December 2010, Erika and I birded at the confluence of the St. Croix and Mississippi rivers.  With few exceptions we were disappointed with the variety and numbers of birds.  I was just about to complain when this merganser, looking like a snorkeler with his/her face under water, swam close by the shore. 
Mergansers in this plumage can be difficult to distinguish.  Several field marks clinch the identification of this bird as a Common Merganser.  First, the brown head color ends sharply where it meets the gray/white of the breast and neck.  Next, the bill, although long and narrow as in all mergansers, is relatively thick, especially at its base.  Finally, the amount of white in a merganser's face is variable, with juveniles such as this one having much more white between the bill and the eyes than nonbreeding adults.  In all nonbreeding plumages, Common Mergansers' white throats contrast sharply with their brown heads.

The Red-breasted Merganser is the species mostly likely to be confused with a Common Merganser.  We were surprised, when we crossed out of Prescott, Wisconsin, and back into Minnesota, to find two Red-breasted Mergansers.  Red-breasted Mergansers do not usually winter in Minnesota (at least away from Lake Superior).  In my next post, I will show you photos of these birds and review their field marks.

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