A practical guide to bird watching in Sonoma County, California

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


Among the gulls that are mostly winter visitors to Sonoma County. Actually most common during spring and autumn migration, but migrating birds usually pass well off-shore (sometimes in very large but effectively inconspicuous flocks), so most sightings at the coast are of wintering rather than migrating birds. A few birds may be present in the summer months, but relatively scarce. Erratic. During years of heavy migration, more birds are likely to be seen at the coast and stopping over at ponds, lakes, flooded fields, or the like further inland. Probably most reliably seen at Bodega Bay, particularly off Bodega Head during migration and occasionally in the Doran Beach/Campbell Cove area in the winter. Often present in the winter at Hudeman Slough. Also seen occasionally in the winter at Shollenberger Park and at the Lakeville Highway sewer ponds (adjacent to Ellis Creek Water Recycling Facility; although these are not open to the public). Not generally attracted to dumps, parking lots, campgrounds, etc. Breeds in south Alaska and interior Canada, and, unlike any other gull, nests in trees--usually conifers near water.

We most often see Bonaparte’s Gull in winter plumage (as shown above). A small gull--smaller even than Mew Gull (Larus canus), which is the smallest gull we see in Sonoma County with any regularity. Agile flyer--often described as tern-like in flight--and buoyant in the water, but its comparatively short, narrow, black bill should distinguish it from our common terns, except Forster’s Tern (Sterna forsteri). Adults in breeding plumage have a black hood. Loses the hood in winter. In winter plumage the head is mostly white but with a distinct black “ear patch” behind the eye. May be very pale grey at the hind-neck. The ear patch is a feature shared by a few other gulls and kittiwakes, most of which are quite rare in the county; a winter gull here with this feature is most likely Bonaparte’s Gull. In phalaropes with similar head markings the dark spot is horizontal and bar-like and includes the eye (See Red Phalarope (Phalaropus fulicaria) and Red-necked Phalarope (Phalaropus lobatus)--confusingly, however, Bonaparte’s Gull may spin on the surface of water like a phalarope). Similar to Forster’s Tern in winter plumage, but the black patch in Forster’s Tern includes an area around the eye. Otherwise, Bonaparte’s Gull in winter plumage has a white neck (sometimes washed with very pale grey at the back), medium grey mantle, and white underparts. Folded wingtips black without large, white “windows” seen in many gulls (may have very small ones). Legs pink to reddish.

Moved to the genus Chroicocephalus, from Larus, in July 2008. Older reference sources (and many until around 2012) will call this bird Larus philadelphia.

In flight, pale underneath, but in adult birds note the white outer primaries creating a wedge of white at the tip of the wings, fringed with black at the trailing edge of the wingtip (as in the photo above; Hudeman Slough, February 2, 2013). Same pattern visible from above. The white outer primaries may show as a wedge of white alongside the tail in the folded wings of a bird at rest. Tail of adult birds is all white in all plumages. Gains full adult plumage in its second year. First-year birds, like the bird pictured at the top of this page (and the bird below), will show brownish grey scapulars. In flight, first-year birds show a distinctive black trailing edges on the entire wing and a dark terminal band on the tail (photo below).

Trivia: Named after Charles Lucien Bonaparte, a French biologist and ornithologist, not Napoleon--although Charles Lucien was a nephew of Napoleon.

Selected county sightings: Spud Point Marina (May 23, 2013, Dan Nelson); Porto Bodega (Apr 26, 2013, Lisa Hug); Hudeman Slough (Feb 2, 2013, Colin Talcroft); Hudeman Slough (Jan 31, 2013, Colin Talcroft); Doran Beach (Jan 8, 2013, Peter Colasanti); Doran Beach (Dec 27, 2012, Colin Talcroft); Doran Beach (Dec 26, 2012, Dea Freid); Bodega Head (Nov 22, 2012, Scott Carey); Bodega Head (Nov 14, 2012, Scott Carey); Shollenberger Park (Sep 2, 2012, Gene Hunn); Shollenberger Park (Aug 24, 2012, Daniel Edelstein); Shollenberger Park (Aug 13, 2012, Lisa Hug); Shollenberger Park (Aug 13, 2012, Lisa Hug); Shollenberger Park (Aug 10, 2012, Scott Carey); Shollenberger Park (July 26, 2012, Rich Stallcup); Ellis Creek Water Recycling Facility (Apr 7, 2012, Colin Talcroft); Hudeman Wetlands (Mar 4, 2012, Michael Park); Hudeman Wetlands (Feb 6, 2012, Dominik Mosur); Hudeman Wetlands (Dec 30, 2011, Logan Kahle)

Further reading:

Bolander and Parmeter, Birds of Sonoma County California, rev. ed., 2000, p. 61

Brinkley, National Wildlife Federation Field Guide to Birds of North America, 2007, p. 123

Dunn and Alderfer, eds., National Geographic Field Guide to the Birds of North America, 5th ed., 2006, pg. 200

Dunn and Alderfer, eds., National Geographic Field Guide to the Birds of North America, 6th ed., 2011, pg. 214

Howell and Dunn, Gulls of the Americas, 2007, pp. 20, 48, 49-52, 53, 69, 70,  301, 302-305

Dunne, Pete Dunne’s Essential Field Guide Companion, 2006, p. 258-259

Ehrlich, Dobkin, and Wheye, The Birder's Handbook, paperback edition, 1988, pg. 162

Fix and Bezener, Birds of Northern California, 2000, p. 171

Floyd, Smithsonian Field Guide to the Birds of North America, 2008, p. 194

Kaufman, Field Guide to Birds of North America, 2000, p. 84

Kaufman, Advanced Birding, 1990, pp. 102-108 (general notes on gull ID), pp. 103

Kaufman, Field Guide to Advanced Birding, 2011, pp. 242-263 (general notes on gull ID), pp. 71, 85, 251, 255, 259, 261, 262, 263

Lukas, Bay Area Birds: From Sonoma County to Monterey Bay, 2012, p. 121, 122

Parmeter and Wight, Birds of Sonoma County California, Update (2000-2010), 2012, p. 34

Peterson, Birds of Eastern and Central North America, 5th ed., 2002, p. 174-175, 180

Peterson, Field Guide to Birds of Western North America, 4th ed., 2010, p. 170-171, 172, 180

Peterson, Western Birds, 3rd ed., 1990,  p. 96, 102-103

Sibley, Field Guide to Birds of Western North America,1st ed., 2003, p. 182

Stokes, Stokes Field Guide to the Birds of North America, 1st ed., 2010, p. 296-297

Vuilleumier, American Museum of Natural History, Birds of North America: Western Region, 2011, p. 173

Voice: Cornell Lab of Ornithology: All About Birds--Bonaparte’s Gull




© Colin Talcroft, 2009, 2010, 2011, 2012, 2013, 2014

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.


Bonaparte’s Gull (winter plumage, 1st-year bird), Doran Beach, Bodega Bay, December 27, 2012

Bonaparte’s Gull

Chroicocephalus philadelphia

1990-2013 Sonoma County data. Graph provided by eBird (www.ebird.org), generated May 30, 2013

EBird reported occurrence in Sonoma County

Bonaparte’s Gull (1st-year bird), Santa Cruz County, May 26, 2014

Note dark scapulars, black trailing edge of wing, black terminal band on tail