LOONS Gaviidae
The Loons are a small and ancient group of birds. They are specialized fish eaters with dagger-like bills that spend most of their time in water. They have lobed feet set so far back on the body that they are very clumsy on land. All five species are restricted to the northern hemisphere and all are migratory, spending the winter in coastal harbors and bays in temperate climes. During the winter they sport a plain non-breeding dress like this Common Loon (left), but all species molt into a striking alternate plumage before departing for the northern breeding grounds in spring, as has this Pacific Loon (below). Both of these photos were taken from wharves in Monterey harbor, California, a great spot for loon watching. Indeed, my friend the late great Roger Tory Peterson considered the loon photographic opportunities here the finest he'd ever seen.

The Pacific Loon (right) in Monterey Bay is not usually inside the harbor. Rather, flocks forage together beyond the kelp line. This makes it the most difficult loon to study closely (because it is the farthest offshore) but in truth it is by far the most common species in California. Some 90% of the thousands of loons that migrate up and down the California coast in spring and fall are Pacific Loons. It is closely related to the Arctic Loon G. arctica of the Old World. In breeding plumage its very pale gray nape is distinctive; in non-breeding plumage it lacks the white flank patch of Arctic; and at all times it has a decidedly thinner bill and more rounded head; good identification discussions of this field problems are in Reinking & Howell (1993) and Birch & Lee (1997), and I even published a small note (Roberson 1989).
Knowing all the plumages of all five species of loons is important in California where three species are regular; Arctic Loon is a super-vagrant; and the fifth species, Yellow-billed Loon (left) is a rare but regular vagrant, averaging perhaps 1-2/year. This particular individual has a special history because it returned to the same spot -- about a half-mile offshore my hometown of Pacific Grove -- for six consecutive years from winter 1993-94 to winter 1998-99. It would appear each year in November in full breeding plumage (as in this photo) and would always be first spotted by Richard Ternullo from his fishing boat. Then the loon would molt into basic plumage for the winter but would change back into breeding plumage by the time in left in March.
Loon migration is impressive, and one also needs to learn the i.d. of loons in flight. The basic-plumaged Red-throated Loon (below) has a very thin bill, comparatively small feet, a pale plumage and a prominent white flank patch.
There has been much study of the breeding biology and ecology of the Common Loon (right) [called the "Great Northern Diver" in the Old World]. It is the "state bird" of Minnesota and its weird echoing cry on the breeding grounds is a classic sign of wilderness there and elsewhere in the forested northlands. Because the use of motor boats on northern lakes negatively impacts breeding populations, there has been much concern for its protection recently (it also used to nest in northeast California long ago). The Loon Society, now known as the North American Loon Fund, arose in the northeast U.S. to help protect Common Loons. Now it but has broadened its interest and support of research to all species. Check their web site home page for many more details, including links to introductory biology of all American species.
The plumages of loons change dramatically from the wintering Common Loon (at upper left) to the summer dress at right. Individuals change at different paces (perhaps related to where they nest); oddly, the photos at top left and at right were taken on the very same day in the Monterey harbor where it is great fun to watch their molt during late winter and spring. Juvenal plumage resembles the adult's winter (=basic) plumage, but most species differ in having the back decidedly barred, as on this juvenal Pacific Loon (below). Note that even in this plumage the nape and back of the neck are paler than the dark sides to the neck, another feature useful for separating Pacific from Arctic Loon.
I would be remiss if I didn't mention the current controversy about the relationship of loons to other groups of birds. Traditionally, loons are considered one of the oldest groups of birds and placed near the front of the taxonomic order near grebes, penquins, and procelarids. Sibley & Ahlquist (1990 and Sibley & Monroe (1990), using biochemical techniques, considered them more closely related to shorebirds and alcids, and therefore placed them somewhere in the middle of their listings (at the end of the Charadriiformes). The most recent A.O.U. Check-List (AOU 1998) considers the latter arrangement "highly controversial" and prefers to "retain [loons] in their current position (i.e., at the front of the list) until their relationships are resolved."

Photos: The basic-plumaged Common Loon Gavia immer was in the harbor at Monterey, Monterey Co., California, on 10 Mar 1983; the breeding-plumaged Pacific Loon G. pacifica was at the same spot back on 1 May 1978. The breeding-plumaged Yellow-billed LoonG. adamsii was just offshore Lovers Pt., Pacific Grove, on 13 Nov 1995 (from Richard Ternullo's boat). The flying Red-throated LoonG. stellata was over Monterey Bay in Nov 1985. The alternate-plumaged Common Loon G. immer was in the harbor at Monterey, California, on 10 Mar 1983. The juvenal-plumaged Pacific Loon was in a drainage ditch (a very odd spot for a loon) near Pajaro Dunes, Santa Cruz Co., California, in Dec 1982. All photos © 2000 Don Roberson; all rights reserved.

Bibliographic note:

There is no "family book" per se (there are numerous coffee-table "survey" books that include Loons among other waterbirds) although there are numerous books devoted to the Common Loon. An introduction to the family, with a few fine photos, is in Carboneras (1992). However, this particular family essay is weak when compared to other families in the Handbook of the Birds of the World series, and the author uses a very out-moded taxonomy which lumps Pacific and Arctic loons.

Literature cited:

American Ornithologists' Union. 1998. Check-list of North American Birds. 7th ed. A.O.U.,  Washington, D. C.

Binford, L. C., and J. V. Remsen, Jr. 1974. Identification of the Yellow-billed Loon (Gavia   adamsii). W. Birds 5:111-126.

Birch, A., and C-T. Lee. 1997. Arctic and Pacific Loons. Birding 29: 106-115.

Carboneras, C. 1992. Family Gaviidae (Loons) in del Hoyo, J., Elliott, A., & Sargatal, J., eds. Handbook of the Birds of the World. Vol. 1. Lynx Edicions, Barcelona.

Reinking, D. L., and S. N. G. Howell. 1993. An Arctic Loon in California. W. Birds 24: 189-196.

Remsen, J. V., Jr., and L. C. Binford. 1975. Status of the Yellow-billed Loon (Gavia adamsii) in   the western United States and Mexico. W. Birds 6: 7-20.

Roberson, D. 1989. More on Pacific versus Arctic loons. Birding 21: 154-158.

Sibley, C. G., and J. E. Ahlquist. 1990. Phylogeny and Classification of Birds: A Study in Molecular Evolution. Yale Univ. Press, New Haven, CT.

Sibley, C. G., and B. L. Monroe, Jr. 1990. Distribution and Taxonomy of Birds of the World. Yale Univ. Press, New Haven, CT.

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