The skimmers are a small family of specialized shorebirds found widely
in the North & South America, Africa, and in India. The three species
are so closely related that some have considered them all one global species,
a situation that recalls others closely-related groupings such as oystercatchers
or the stilts. Skimmers often roost with gulls and terns; an African
Skimmer (above) appears in a huge flock of gulls and terns at an eastern
African river mouth. In the New World, the only species is the Black
Skimmer (left in a great shot by John Sorensen). Sorensen's photo of
this juvenal-plumaged skimmer well shows the modified bill with the lower
mandible extending well beyond the tip of the upper mandible.
Skimmers are social birds, nesting in colonies and usually roosting with gulls and terns (top photo), but they forage alone or in small parties. They are closely related to gulls and terns; indeed, much recent literature follows Sibley & Monroe (1990) in considering them simply a tribe (not even a subfamily) of an expanded Laridae which includes gulls, terns, jaegers, and skimmers. I like the traditional approach that skimmers do constitute a family, an approach used in the on-going Handbook of the Birds of the World series.
Skimmers use these unique bills to scythe estuaries, lakes, large rivers and ponds for small fish. Food is caught almost exclusively by skimmer the water in flight with mouth open and lower mandible submerged; prey items touched by the mandible are grasped while head doubles back under body, and then the fish is swallowed in flight or after landing. As a youth I still recall seeing Frederick Kent Truslow's photo which showed a skimmer in full skimming mood and in focus; a technical accomplishment with 1950s equipment. He had done so by focusing on a floating leaf and waiting until the skimmer passed through this same focal plane (Truslow 1970; the photo has been republished in many other books). I've never spent the time necessary to take a similar shot today (when an autofocus camera permits this type of photo without undue effort) but the Black Skimmer (below) has just grasped a fish and its head is bending back towards its chest as it completes the catch.
|There are three widely separated species of skimmer. The North &
South American bird is the Black Skimmer (above left) and it has
a dark bill tip in all plumages and a black hindneck in breeding plumage;
it is also a bit larger than Old World taxa. The African Skimmer
(above right in a flight shot by Greg W. Lasley) is very similar but adults
have a yellow tip to the red or red-orange bill. The Indian Skimmer Rynchops
albicollis is rather like the African bird but nesting adults have
a white nuchal collar. Alas, these differences break down in the non-breeding
season when all skimmers have white collars around the neck, and young
skimmers of any species can have a dusky tip to the bill. The Indian Skimmer
is classified as "vulnerable" and the total population is only about 10,000
birds (Zusi 1996); it is restricted to the Indian subcontinent with much
smaller numbers locally in southeast Asia. The African and Indian Skimmers,
and the Black Skimmer in South America (two difference races) are primarily
denizens of large rivers. North American skimmers are unique in their dependence
of sandy coasts and barrier islands. They tend to be much scarcer inland,
although they nest at the Salton Sea in the California deserts.
In California, Black Skimmers are undergoing a major range expansion. The first record for the state was in September 1962 on the s. California coast but the real invasion began in 1968 with five at the Salton Sea; 487 pairs nested here in 1995. Breeding in San Diego Bay began in 1976 and in Orange County in 1985. The statewide nesting population was estimated at 1200 pairs in 1995 (Collins & Garrett 1996). The first nesting in San Francisco Bay was in 1994 (Layne et al. 1996) and through the 1990s local observers in my home base (Monterey County) found migrants passing through to the growing S.F. Bay colony. The first Monterey County nesting attempt was in June 2000 (details on my 2000 highlights page). We expect these dynamic expansions to continue or consolidate into new breeding colonies in the future.
Photos: The flock that included an African Skimmer Rynchops flavirostris was at the Sabeki River mouth in eastern Kenya in Nov 1981; the flocks includes Sooty Gulls Larus hemprichii, Great Crested Terns Sterna bergii, and Common Terns S. hirundo. John Sorensen took the fine shot of a juvenal Black Skimmer R. niger at Del Monte Beach, Monterey, California, where it is a rare migrant 27 Sep 2000. The two shots of an adult Black Skimmer are from Alvarado, Alameda Co., California, 20 July 1978, where it was one of the first records in San Francisco Bay. Greg W. Lasley took the flight shot of the adult African Skimmer at Shakawe, Okanvango River, Botswana, on 22 Oct 1998. Top photo and adult Black Skimmers © 2000 D. Roberson, juvenal Black Skimmer © 2000 John Sorensen and flying African Skimmer © 2000 Greg W. Lasley, both used with permission; all rights reserved.
There is no family book per se although skimmers are included in numerous texts which cover gulls and terns and relatives. The account by Zusi (1996) in the Handbook of the Birds of the World series is a fine introduction. Among the fine photos there is a Kevin T. Karlson shot of a skimmer in full mouth-agape skim, recalling the Truslow photo so talked about in my youth.
Clements, J.F. 1991. Birds of the World: A Checklist. 4th ed. Ibis Publ., Vista, CA.
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