Bird of the Month - November 2004
Yellow-billed Loon
Gavia adamsii
Hundreds of thousands of loons occur in California each year, the vast majority along the coast and over nearshore ocean waters. By far the greatest proportion of this throng is represented by Pacific Loons (G. pacifica), which migrate through California waters each spring and fall, wintering in smaller numbers. Common (G. immer) and Red-throated (G. stellata) loons make up nearly all of the remainder and comprise most of the loons spending the winter locally. Five reports of single Arctic Loons (G. arctica) from Asia have been accepted for the state, none from far northwestern California. Completing the list of species is the Yellow-billed Loon. This is the largest and scarcest member of the family, it lives farthest north throughout the year, and it is a ‘bird to see’ in California.
Dating from the first report in the state—a single bird at Inverness, Marin County, in December 1967—Yellow-billed Loons have occurred about 70 times in California, and they have been recorded annually since 1971. Nearly 90% of all accepted reports have been from Monterey Bay northward along the coast. Only four have ever been found inland in California. However, increasing numbers are now detected inland nearly across the continent. This almost certainly owes more to greater numbers of talented birders than to an increase in population or change in wintering distribution of these loons.
In late spring and summer, Yellow-billed Loons are birds of the far north. In North America, they nest on lakes and pools of the tundra from the Seward Peninsula in Alaska to central arctic Canada northwest of Hudson Bay. Most of the birds encountered in California are found from November into late winter. Many are individuals in their first winter of life, but some are adult or adult-like. While some are seen only once, others have remained at the point of discovery for weeks or even months; some have appeared to return to the same location in successive winters. Any Christmas Bird Count team stumbling onto one of these loons has instantly found one of the best birds of the day! Further attesting to the rarity of Yellow-billed Loon in California is that only a very few have ever been detected actually migrating north or south among groups of other loons seen from shore points.
The Yellow-billed Loon closely resembles the Common Loon at all seasons. As is true for many rare species that are similar to other, much more common species, it is best to support an identification of this bird by observing all possible points of distinction. In comparison to Common Loon, the best marks for Yellow-billed Loon in non-breeding plumage are slightly greater size, longer and thicker neck, and a long, pale yellowish or whitish bill which is straight along the top, upcurved along the bottom, and usually pale on all of the outer portion of upper mandible ridge. A dark smudge behind the ear is usually noticeable. This smudge may be neat and well-defined or broad and smudgy. Pale edges to the back feathers are often conspicuous, especially in immatures. Yellow-billed Loons tend to have an ‘alert’ posture because they carry the bill somewhat uptilted, which in turn emphasizes its upswept shape.