Xantus’s Murrelet (Synthliboramphus hypoleucus) is a small auk found in the California Current system in the Pacific Ocean. This small seabird breeds on islands off California and Mexico. The species is named for the Hungarian ornithologist John Xantus de Vesey, who described it from specimens collected off Baja California. It is threatened by predators introduced to its breeding colonies and by oil spills, and is currently listed as vulnerable.
Description and range
The Xantus’s Murrelet is a small black and white auk with a small head and thin sharp bill. It resembles the closely related Craveri’s Murrelet, with which it shares the distinction of being the most southerly living of all the auk species. It breeds in the Channel Islands of California, the largest colony being on Santa Barbara Island, and also several islands off Baja California, including Isla Guadalupe. After the breeding season it disperses north at sea, usually to offshore waters, sometimes even as far as British Columbia.
The Xantus’s Murrelet feeds far out at sea on larval fish like anchovies, sardines and Sebastes rockfish. Like all auks it is a wing-propelled diver, chasing down prey under the water with its powerful wing beats. There is some speculation that it may feed cooperatively in pairs, as it is almost always observed in pairs, even during the breeding season. It flies well, and can take off easily.
The Xantus’s Murrelet nests in small crevices, caves and under dense bushes on arid islands in loosely scattered colonies. Two eggs are laid and the parents return to the colony only at night. Incubation lasts for about a month. Like other murrelets of the genus Synthliboramphus (like the Ancient Murrelet) the chicks are highly independent, leaving the nest within two days of hatching and running actively towards the sea, where the parents call to them. Once at sea the family swims to offshore waters. Little is known about the time at sea due to difficulties in studying them.
The Xantus’s Murrelet is considered by some to be one of the more endangered species of auk. It is threatened by oil spills, as much of its population lives near the busy shipping lanes of Los Angeles. Because a large part of its small population nests in such a small area a single catastrophic oil spill could have far reaching implications. It is also threatened by introduced species such as rats and feral cats; a threat has been lessened lately by efforts to restore its habitat by removing introduced predators. In one case the population of rats was removed from Anacapa Island by the use of poisoned bait (the money for which being paid by an oil settlement trust fund).