Xantus' Murrelet (Endomychura hypoleuca) 



World Breeding Range 



The breeding range of the Xantus' Murrelet 

 is restricted to the Channel Islands and the west 

 coast of Baja California, Mexico. This species and 

 the closely related Craven's Murrelet (Endo- 

 mychura craven) are thought to be reproductively 

 isolated, even though a small zone of sympatry 

 exists in the San Benitos Islands, Mexico (Jehl 

 and Bond 1975). Before intensive research 

 was begun on Xantus' Murrelets in 1 975 by Hunt 

 et al. (1979), little was known about their life 

 history. Most of the information in this account 

 was taken from that study. 



Xantus' Murrelets nest primarily in rock 

 crevices along or near cliff ledges, but also under 

 bushes, in ground vegetation, in abandoned rabbit 

 burrows, under old pelican nests, and in man-made 

 debris (Hunt et al. 1979). These murrelets, unlike 

 most alcids, usually lay two eggs annually. Eggs 

 are incubated under the wings, next to lateral 

 brood patches on each side of the body. 



During the breeding season, Xantus' Murrelets 

 spend daylight hours either in the nest or foraging 

 at sea. Other colony activites, such as nest-site 

 selection, incubation shift changes, and fledging, 

 occur at night (Hunt et al. 1979). Xantus' 

 Murrelet chicks are highly precocial and fledge at 

 about two days of age. The small, flightless, 

 downy young leave their nests at night and scurry 

 to the shoreline. Upon reaching the ocean, they 

 plunge in and head far out to sea with their 

 parents. Chicks waylaid during the night or 



attempting to leave the nests during the day are 

 quickly eaten by Western Gulls. 



Xantus' Murrelets dive for food and feed 

 extensively on larval fish. Northern Anchovies, 

 Pacific Sauries and rockfish (family Scorpaenidae) 

 are the most important species taken by Xantus' 

 Murrelets in the Channel Islands (Hunt et al. 

 1979). Of these, Northern Anchovies are the 

 most important and their availability may 

 dramatically influence the breeding success of 

 Xantus' Murrelets (Hunt and Butler 1980). 

 Xantus' Murrelets often forage in the immediate 

 vicinity of their colonies during the breeding 

 season, but disperse widely thereafter. 



CALIFORNIA COLONIES 



All California colonies of Xantus' Murrelets 

 are in the Channel Islands. Santa Barbara Island 

 (524 008), where 2,000 to 4,000 birds are esti- 

 mated to breed, is the most important colony for 

 this species in California. Hunt et al. (1979) have 

 conducted studies of this species' breeding 

 biology and at-sea distribution at this site. All 

 remaining colonies of Xantus' Murrelets in 

 California are small. Of these, Prince Island (501 

 004) and Sutil Rock (524 009) are the largest, 

 each with 150 birds, followed by East Anacapa 

 Island (502 009) with fewer than 40 birds, Snag 

 Rock (524 007) with 30 birds, and Gull Rock 



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