Synthliboramphus hypoleucus

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	CHARADRIIFORMES	ALCIDAE

Scientific Name:

Synthliboramphus hypoleucus

Species Authority:

Xántus de Vesey, 1860

Common Name/s:

English

–

Xantus's Murrelet

Assessment Information [top]

Red List Category & Criteria:

Vulnerable B2ab(iv,v) ver 3.1

Year Assessed:

2010

Assessor/s:

BirdLife International

Reviewer/s:

Calvert, R., Butchart, S., Bird, J.

Contributor/s:

Whitworth, D., Keitt, B., Tershy, B., Wolf, S.

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.

History:

2008	–	Vulnerable
2007	–	Vulnerable
2005	–	Vulnerable
2004	–	Vulnerable
2000	–	Vulnerable
1988	–	Near Threatened

Geographic Range [top]

Range Description:	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.
Countries:	Native: Canada; Mexico; United States
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	Based on at sea survey data from 1975 to 2003, Karnovsky et al. (2005) were able to estimate a current North American at-sea population of 39,700, of which 17,000 are likely to be mature breeding individuals. Although this estimate is based on extrapolation from survey data, population estimate is perhaps best placed in the 10,000-19,999 category.
Population Trend:	Decreasing

Population:

Based on at sea survey data from 1975 to 2003, Karnovsky et al. (2005) were able to estimate a current North American at-sea population of 39,700, of which 17,000 are likely to be mature breeding individuals. Although this estimate is based on extrapolation from survey data, population estimate is perhaps best placed in the 10,000-19,999 category.

Population Trend:

Decreasing

Habitat and Ecology [top]

Habitat and 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.
Systems:	Terrestrial; Marine

Threats [top]

Major Threat(s):	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.

Major Threat(s):

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 Actions [top]

Conservation Actions:	Conservation Actions 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 Endangered in Mexico and Threatened 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. A pilot habitat restoration for the species has begun on Santa Barbara Island²². Conservation Actions 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.

Conservation Actions:

Conservation Actions 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 Endangered in Mexico and Threatened 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. A pilot habitat restoration for the species has begun on Santa Barbara Island²².

Conservation Actions 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.

Citation:	BirdLife International 2010. Synthliboramphus hypoleucus. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 09 February 2012.
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