A practical guide to bird watching in Sonoma County, California

(Unless otherwise indicated, all phone numbers are in the 707 area code)


Red-breasted Merganser

Mergus serrator

Fairly common in Sonoma County in the winter months. Migrants usually start arriving in late October. The bulk of overwintering birds leaves by late April. Usually not present in the summer, but has been recorded occasionally. Favors coastal habitats close to shore, protected bays, estuaries. Occasionally found inland, where it favors large reservoirs and lakes, usually during migration. Gregarious. Often seen in small flocks. Sometimes fishes cooperatively. May associate loosely with loons and grebes. Eats mostly fish, but also aquatic insects and small crustaceans.  Perhaps best observed in the county at Bodega Bay, especially near Campbell Cove and Porto Bodega.

Red-breasted Merganser, like Common Merganser (Mergus merganser), shows strong sexual dimorphism. That is, the males and females of the species look quite different. Adult males have a green head, a distinct white collar at the base of the neck, and a brownish, streaked breast. The male's back is black and its sides grey, but the back and sides are separated by a bold white horizontal stripe, and there is an area of black and white checkered patterning on the back just behind the neck. Reddish eye. Thin, slightly upturned, reddish-orange bill. Most conspicuous, however, is the bird's shaggy crest, often in two tufts (although just after diving, the crest may be smoothed down, as in the photo of the female above). Male Common Merganser has a green head, but without a crest, and its breast is quite white. Male Common Merganser also has a heavier, brighter red bill, and it is an altogether chunkier bird (comparison photo below).

Female Red-breasted Merganser, like the male, has a shaggy double crest, but the head and crest are a dull greyish brown, rather than green. Females are otherwise mostly brownish grey. Female Common Merganser, has a shorter, more compact crest and the crest and head are a bright rust color. Female Common Merganser is otherwise mostly a clear silvery grey (comparison photo below). Generally speaking, Red-breasted Mergansers (both male and female) are thinner, rangier looking birds than Common Mergansers and they give the impression of being somewhat unkempt. First-year male Red-breasted Mergansers look much like adult females but will show broken black streaking at the chin.

Selected county sightings: Campbell Cove (January 11, 2012; Colin Talcroft); Porto Bodega (January 8, 2012, Colin Talcroft); Bodega Head (October 15, 2011, Alan Wight); The Bird Walk (March 3, 2011, Dea Freid); Bodega Bay (October 25, 2010, Scott Carey)

Further reading:

Bolander and Parmeter, Birds of Sonoma County California, rev. ed., 2000, p. 37

Brinkley, National Wildlife Federation Field Guide to Birds of North America, 2007, p. 54

Dunn and Alderfer, eds., National Geographic Field Guide to the Birds of North America, 5th ed., 2006, p. 48

Dunn and Alderfer, eds., National Geographic Field Guide to the Birds of North America, 6th ed., 2011, p. 46

Ehrlich, Dobkin, and Wheye, The Birder's Handbook, paperback edition, 1988, p. 94

Fix and Bezener, Birds of Northern California, 2000, p. 101

Kaufman, Field Guide to Birds of North America, 2000, p. 42

Kaufman, Advanced Birding, 1990, pp. 49, 50

Kaufman, Field Guide to Advanced Birding, 2011, pp. 150, 152

Peterson, Birds of Eastern and Central North America, 5th ed., 2002, p. 80, 82

Peterson, Field Guide to Birds of Western North America, 4th ed., 2010, p. 40, 44

Peterson, Western Birds, 3rd ed., 1990,  p. 60, 68

Sibley, Field Guide to Birds of Western North America,1st ed., 2003, p. 68

Vuilleumier, American Museum of Natural History, Birds of North America: Western Region, 2011, p. 68

Voice: Cornell Lab of Ornithology: All About Birds--Red-breasted Merganser



© Colin Talcroft, 2009, 2010, 2011, 2012

Unless noted, all photos by the author. If you would like to use one of my images, please ask for permission for non-commercial use with proper credit or commercial use with proper compensation.


Female Red-breasted Merganser, Campbell Cove, Bodega Bay, January 11, 2012

For comparison: Female Common Merganser

Lake Ralphine, Santa Rosa, December 17, 2009

Note: Rich rust-colored head; white chin and breast; heavier, redder bill; silver grey back and sides

For comparison: Male Common Merganser

Lake Ralphine, Santa Rosa, December 17, 2009

Note: Lack of crest; heavier, redder bill;

white breast and sides