(c) Glen Tepke
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This small bird of coastal Pacific waters is among the world's rarest seabirds. It is also among the most threatened, nesting in as few as 10 locations. Rarely seen from the coast, Xantus's Murrelets prefer the deep, warm offshore waters of the Pacific. They breed much further south than most other members of the alcid family.
The Xantus's Murrelet is a diminutive bird.At just under 10 inches in length, it is slightly smaller than an American Robin. Adults have a 15-inch wingspan and weigh only six ounces. Black above and white on the chin, throat, and belly, Xantus's Murrelet is very similar in appearance to Craveri's Murrelet, a species that shares a similar range. The two are most easily separated in flight by the distinct white underwing of the Xantus's.
This species is fond of warm, southerly climates. During the breeding season, the entire Xantus's Murrelet population is concentrated within a fairly small region off the coasts of southern California and Mexico. The American population nests entirely within California's Channel Islands, while the Mexican population nests primarily on the Baja California islands of San Benito and Guadalupe.
During the breeding season, Xantus's Murrelets nest on the steep slopes and cliffs of rocky offshore islands. They prefer areas with sufficient vegetation for cover. Away from the breeding season, the birds move far out to sea, preferring the deep waters beyond the continental shelf.
Xantus's Murrelets feed by diving and swimming underwater in pursuit of small fish and crustaceans. Interestingly, they are nearly always observed feeding in pairs rather than in flocks. This curious feeding strategy takes place year round, including during the breeding season. Since one member of each breeding pair is at the nest throughout the breeding season, unrelated birds may pair up to feed cooperatively.
In early spring, females lay two eggs directly on the ground, usually in a rocky area concealed by dense vegetation. No actual nest is constructed. For about 34 days, both parents take turns incubating the eggs, which vary widely in color, from pure white to blue, green, or even dark brown. Some are heavily spotted, while others are unspotted. The eggs are also extremely large, weighing up to a quarter of the mother's total body weight—among the largest parent to egg size ratio of any bird. The chicks emerge fully feathered and well developed. They generally spend fewer than 48 hours at the nest site, during which time they are not fed. By the second or third night, the parents coax the chicks away from the nest site, then fly out to sea, leaving the chicks to find their own way to the ocean. The chicks' path often involves a daunting climb over rough terrain, and down steep, rocky slopes. Xantus's chicks have been noted leaping from cliffs as high as 200 feet into the waters below! Once in the ocean, the chicks find their parents, who wait beyond the surf, calling for them constantly. Reunited, adults and chicks swim out to sea, where the parents continue to tend to the chicks for several months.
Once the breeding season ends, the birds move out to sea, following the warm offshore California current. Though most remain off the coast of central California, a few occasionally move north as far as British Columbia. This movement is generally regarded as a post-breeding dispersal rather than a true migration. Young birds are flightless and slow moving at this time.
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Synthliboramphus hypoleucus. Downloaded from http://www.birdlife.org on 5/11/2006
Drost, C. A., and D. B. Lewis. 1995. Xantus's Murrelet (
Synthliboramphus hypoleucus). In
The Birds of North America, No. 164 (A. Poole and F. Gill, Eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.
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Whitworth, D.L., J.S. Koepke, H.R. Carter, F. Gress, and S. Fangman.
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Xantus's Murrelets (Synthliboramphus hypoleucus) at Anacapa Island, California: 2005 annual report. Unpublished report, California Institute of Environmental Studies, Davis, California (prepared for the American Trader Trustee Council and Channel Islands National Park). 24 pp.
