Scientific Name
Synthliboramphus hypoleucus
Introduction
This unique small bird of coastal Pacific waters is among the world’s rarest seabirds. The park is the nesting location for about a third of the world’s population. 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.
Quick and Cool Facts
- Xantus’s murrelet come ashore only to breed, remaining at sea the rest of the year.
- The park has 80% of the U.S. breeding population of Xantus’s murrelets.
- Santa Barbara Island has the largest Xantus’s murrelet colony in the United States, and possibly the world.
- Xantus’s murrelets nest primarily in natural rock crevices along steep edges around the periphery of islands.
- Females lay two eggs containing 22% of her body weight which are incubated for about a month.
- The chicks emerge from eggs fully feathered and well developed.
- The chicks spend fewer than 48 hours at the nest site and are not fed.
- A Xantus’s murrelet chick will leave the nest for the open ocean at two days old tumbling down steep slopes and cliffs to reunite with parents in the water.
- The Xantus’s murrelet was listed as a threatened species by the state of California on December 22, 2004.
Appearance
The Xantus's murrelet is a small bird. At 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 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. However, birds disperse after breeding, sometimes as far north as British Columbia. Eighty percent of the U.S. breeding population of Xantus’s murrelets (33.5% of the world’s population and the only breeding ground north of Mexico) occurs on the Channel Islands, while the Mexican population nests primarily on the Baja California islands of San Benito and Guadalupe.
Habitat
During the breeding season, southern California’s Xantus’s murrelets, who are crevice and burrow nesters, lay their eggs on the steep slopes and cliffs of Anacapa and Santa Barbara 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. Adults are active at the colony only at night. 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 seen 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.
Please see Xantus's murrelet nestcam video at bottom of page.
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 relocate as far north 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.
Conservation Status
According to the International Union for Conservation of Nature – 2010 Red List of Threatened Species, this species is considered to have a vulnerable status because of its limited range and small, declining population. Several colonies have gone extinct, and introduced predators are causing declines in some of the remaining nine colonies. Channel Islands National Park has implemented several restoration projects to reverse these declines. On Santa Barbara Island, after feral cats were removed in 1978, numbers of Xantus’s murrelets increased to approximately 1,500 in 1992. Additional work on Santa Barbara Island includes restoring seabird nesting habitat by removing non-native plants and planting native vegetation. On Anacapa Island, the National Park Service eradicated the introduced black rat population that had decimated the population of nesting Xantu’s murrelets. Notably in 2009 the number of Xantu’s murrelet clutches on Anacapa increased 61% over the previous year. Visit Seabirds for more information about restoration activities in the park.
Links for Additional Information
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