Justification This species is considered Vulnerable because of its small range and small, declining population. Several colonies have gone extinct, and introduced predators are causing declines in some of the remaining nine colonies. Conservation action is beginning to have some positive effects, and the continuing eradication of introduced predators from existing colonies, the discovery of new colonies and/or the recolonisation of former colonies may eventually result in a downlisting to Near Threatened.

Family/Sub-family Alcidae

Species name author Xántus de Vesey, 1860

Taxonomic source(s) AOU checklist (1998 + supplements), Sibley and Monroe (1990, 1993), Stotz et al. (1996)

Synonyms Brachyramphus hypoleuca Collar and Andrew (1988), Brachyramphus hypoleucus Stotz et al. (1996)

Identification 24 cm. Small, black-and-white alcid. Black upperparts. White underparts. White underwing linings. Black on head extends to bill. Partial white eye-ring. Shortish, stout bill. Nominate subspecies has more extensive white on face and ear-coverts, forming crescent in front of and over eye. Similar spp. Craveri's Murrelet S. craveri has partial breast- band, black extending under bill and different underwing colour and bill shape. Voice Shrill whistle, sometimes given as series.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

10,000-19,999

decreasing

769,000 km²

No

Range & population Synthliboramphus hypoleucus breeds off the coast of southern California, USA and Baja California, Mexico. Based on data from aerial and boat surveys between 1975 and 2003, the world population has been estimated at 39,700, of which 17,000 are likely to be breeding in any given year¹⁴. In the USA an estimated 885-2,575 breeding pairs occur, the biggest colony on the island of Santa Barbara holds 500-1,250 pairs¹¹. Small numbers breed on Anacapa (200-600 pairs), Santa Cruz (100-300 pairs), San Miguel (50-300 pairs), and San Clemente islands (10-50 pairs), USA^1,3,4,9. Nesting is suspected at Santa Catalina Island (25-75 pairs)¹¹. The Santa Barbara colony has been stable since the 1980s, but recent surveys suggest a decline¹¹. In Mexico, it is known to breed on Los Coronados (750-1,250 pairs), San Jeronimo, San Benito (250-500 pairs), and two islets offshore of Guadalupe Island. Nesting was also recently confirmed on Todos Santos²⁰, and may also occur on the San Martin islands based on vocalizations heard during the breeding season. There are two distinct subspecies, the southern form breeding on only the three San Benito Islands and two rocks offshore of Guadalupe Island. Other likely former breeding colonies (Cedros, Natividad, Asuncion and San Roque) have been extirpated by invasive animals¹¹. Both subspecies breed sympatrically on the San Benito Islands, and the presence of intermediates suggests that some mixing takes place, although most mating is apparently assortive¹⁷. Post breeding birds disperse north and have been recorded in some number in late summer off British Columbia, Canada¹².

Ecology: It nests on steep sea-slopes, canyons and cliffs with a sparse cover of herbaceous and shrubby plants³. It is a generalist predator, and may exploit higher prey concentrations around pelagic convergence lines¹³. Around Santa Barbara, it feeds on larval fish, especially northern anchovy Engraulis mordax^4,5. Breeding effort and performance are lower when anchovy abundance is low⁵.

Threats Invasive mammals were responsible for all known and suspected colony extinctions and in 1995 were present on all the larger colonies and former colonies but Santa Barbara Island⁷. There was heavy cat predation on North Coronado until the mid-1990s^3,6. Black rats Rattus rattus almost extirpated the species from Anacapa³, but have now been successfully erradicated¹⁵. The most significant current threat to Xantus's Murrelet recovery is the presence of invasive cats on Guadalupe Island, likely the most important historical site for the southern subspecies¹⁸. House mice were recently introduced the the Coronados Islands and deermice (native to nearby Cedros Island) have also been introduced to the San Benito Islands. Deer mice predate eggs on Santa Barbara⁸. All Xantus's breeding colonies in California are legally protected as National Parks, private protected areas or military bases. In Mexico, however, only the three southernmost former breeding islands were legally protected, while all current breeding islands were not protected¹⁷. Pollution from offshore oil-wells or the Los Angeles oil-tanker lane could extirpate the species from the south California Bight³. Further threats are drowning in drift gill-nets, nest-site disturbance, bright lights used by the squid fishery that cause disturbance and mortality and possibly organochlorine pollution³. The 80% decline in zooplankton off southern California from 1951 to 1993 may be detrimental to the species. Changes in sea temperature associated with global climate change could have an impact on food availability in future²¹.

Conservation measures underway All potential breeding islands in the USA and Mexico have been surveyed, with the exception of the offshore rocks of Cedros Island¹⁰. Over the past 10 years, most invasive mammals, including cats, rats, goats, sheep, rabbits, donkeys and dogs have been removed from almost all islands that are known current or suspected historical nesting sites in the US and Mexico ^{7,11,15,16,19}. The most important remaining conservation action is to eradicate cats from Guadalupe Island. Because of its large size and lack of native mammals, Guadalupe may have been the largest Xantus's Murrelet breeding colony and was very likely the most important colony for the southern subspecies. The Xantus's Murrelet is currently listed as threatened in Mexico and under the California Endangered Species Act, and is currently a candidate species for federal listing in the USA²¹. In 2003, fishing and other extractive uses was banned within important areas of the Channel Islands National Marine Sanctuary in an attempt to reduce light and noise pollution in important near-shore staging areas. However, the exclusion zone covers only a small buffer area around some colonies, and may be ineffective at minimising threats²¹. Guadalupe Island has just been declared a Biosphere Reserve (thanks to Conservacion de Islas)¹⁰. The remaining Mexican islands with current or former breeding colonies are either in existing biosphere reserves (Natividad, Asuncion and San Roque) or in a proposed new biosphere reserve. This is the first step to regulating tourism and the more damaging impact of commercial fishers¹⁰.

Conservation measures proposed Eradicate introduced predators on other small islands³, including ground squirrels from Natividad Island, invasive house mice from Coronados Island and recently introduced deermice from the Western San Benito Island¹⁸. Develop strategies to remove predators from larger islands, with a particular focus on removing cats from Guadalupe Island¹⁸. Develop contingency plans to prevent the establishment of new predator populations³. Survey remaining potential breeding islands³. Continue to monitor population trends with precision³. Regulate tourism on Baja California islands³. Assess the impact of gill-net fisheries³. Conduct further studies to determine levels of genetic differentiation and the extent of mixing between the two subspecies to clarify their taxonomic status.

References 1. Carter et al. (1992). 2. DeLong and Crossin (1968). 3. Drost and Lewis (1995). 4. Hunt et al. (1981). 5. Hunt and Butler (1980). 6. Jehl and Bond (1975). 7. McChesney and Tershy (1998). 8. Murray et al. (1983). 9. Sowls et al. (1980). 10. B. Tershy in litt. (1999). 11. B. Keitt and D. Whitworth in litt. (2003). 12. Gaston and Jones (1998). 13. Hamilton et al. (2004). 14. Karnovsky et al. (2005). 15. Whitworth et al. (2005). 16. Keitt (2005). 17. Wolf et al. (2006). 18. B. Tershy in litt. (2007). 19. Aguire et al. (in press). 20. B. Keitt in litt. (2007). 21. S. Wolf in litt. (2007).

Further web sources of information

Audubon WatchList

Text account compilers Phil Benstead (BirdLife International), Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International), David Capper (BirdLife International), James Gilroy (BirdLife International), Matt Harding (BirdLife International)

Contributors Brad Keitt (Island Conservation), Bernie Tershy (Island Conservation), D. Whitworth (Island Conservation), Shaye Wolf (Center for Biological Diversity)

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Synthliboramphus hypoleucus. Downloaded from http://www.birdlife.org on 10/2/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

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