Xantus's Murrelet

Synthliboramphus hypoleucus

(c) Glen Tepke
  • ALCIDAE
  • Auks, Murres, Puffins, Guillemots
  • Charadriiformes
  • Pato nocturno de Xantus
  • Guillemot de Xantus
Introduction
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.
(c) Glen Tepke
Appearance Description

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.

Range Map
Courtesy Kenn Kaufman
Range Distribution
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.
Habitat

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.

Feeding

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.

Reproduction

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.

Migration

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.

  • 5,600
  • 5,600
Population Status Trends
Xantus's Murrelet numbers have been decreasing over the past century. Their historically small range has also been shrinking as populations have been eliminated entirely from certain locations. While overall trends have been negative, the Xantus's Murrelet has rebounded somewhat in recent years on islands where sound conservation measures have been employed.
Conservation Issues
Xantus's Murrelets are impacted by a number of threats. Much of their small population lives and breeds along the busy shipping lanes of southern California's major port cities, where they are particularly vulnerable to pollution. A single oil spill could prove disastrous to all Channel Island breeding colonies.
 
A more tangible threat has been the recent introduction of non-native species to every single island where Xantus's Murrelets nest. Habitat destruction and depredation of eggs and young by introduced species have driven the murrelets entirely from some breeding colonies, and reduced their numbers drastically at many others. In 1978, the removal of feral cats from Santa Barbara Island resulted in an increased murrelet population. Since then, a major effort has been underway to remove introduced rats, cats, rabbits, sheep, goats, and pigs from Xantus's Murrelet nesting colonies. The murrelets have responded well. Results from California's Anacapa Island have been particularly encouraging. Prior to 2002, when black rats were removed from the island, over half of all murrelet nests were eliminated by predators. Since 2002, monitoring surveys indicate that breeding efforts and nesting success have increased dramatically. The number of murrelet nests found on Anacapa Island increased 81% between 2003-2005. While over half of all nests were destroyed by predation prior to 2002, none have been lost since. Similar programs may yield equal success at the remaining breeding colonies.
 

Fortunately, the entire U.S. Xantus's Murrelet population, as well as over half of the Mexican population, breeds on protected lands within Audubon-designated Important Bird Areas. The species has been listed as threatened in Mexico, and received further protection in December 2004, when it was listed as threatened by the California Fish and Game Commission.

What You Can Do
More Information
Read more about the efforts of California's Anacapa Island Xantus's Murrelet Monitoring Team.
Natural History References
Bent, A. C. 1919. Life Histories of North American Diving Birds. U.S. Natl. Mus. Bull. 107.

BirdLife International (2006) Species fact sheet: 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.
 
Kaufman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company, New York.
 
Whitworth, D.L., J.S. Koepke, H.R. Carter, F. Gress, and S. Fangman. Nest monitoring of
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.
Conservation Status References
Bent, A. C. 1919. Life Histories of North American Diving Birds. U.S. Natl. Mus. Bull. 107.

BirdLife International (2006) Species fact sheet: 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.
 
Kaufman, Kenn. 1996. Lives of North American Birds. Houghton Mifflin Company, New York.
 
Whitworth, D.L., J.S. Koepke, H.R. Carter, F. Gress, and S. Fangman. Nest monitoring of

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.