Synthliboramphus hypoleucus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Charadriiformes Alcidae

Scientific Name: Synthliboramphus hypoleucus Xántus de Vesey, 1860
Common Name(s):
English Guadalupe Murrelet
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Taxonomic Notes: Synthliboramphus hypoleucus and S. scrippsi (del Hoyo and Collar 2014) were previously lumped as S. hypoleucus following Sibley and Monroe (1990, 1993).
Identification information:

Assessment Information [top]

Red List Category & Criteria: Endangered B2ab(iv,v) ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Keitt, B., Tershy, B., Whitworth, D. & Wolf, S.
Facilitator/Compiler(s): Anderson, O., Benstead, P., Bird, J., Butchart, S., Calvert, R., Capper, D., Gilroy, J., Harding, M., Sharpe, C J, Symes, A. & Taylor, J.
This newly split species is listed as Endangered because it occupies a very small range when breeding, nesting on only a very few islands and islets, and is inferred to be in on-going decline owing mainly to the impacts of invasive mammalian predators. If it is found to be breeding at more than five locations, the species may warrant downlisting to a lower threat category.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Synthliboramphus hypoleucus breeds along the west coast of Mexico, on the three San Benito Islands, Guadalupe Island and at least two associated offshore rocks (Birt et al. 2012, Chesser et al. 2012). Cat predation is thought to have caused the extirpation, or at the very least, significantly reduced the population on the main island of Guadalupe (Keitt et al. 2006), which is considered the most important historical site for the species (B. Tershy in litt. 2007). Other likely former breeding colonies (Cedros, Natividad, Asunción and San Roque) are thought to have been extirpated by invasive animals (B. Keitt and D. Whitworth in litt. 2003). Breeding is unconfirmed on San Martín Island, Baja California, and San Clemente and Santa Barbara islands, California (Chesser et al. 2012). The species winters offshore, with presumably the majority of the population remaining in the vicinity of the breeding range along the western coast of Baja California (Chesser et al. 2012). Some post-breeding birds disperse north to the coasts of California and Oregon, USA (Gaston and Jones 1998).

Countries occurrence:
Mexico; United States
Additional data:
Estimated area of occupancy (AOO) - km2:340Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:469000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:2-5Continuing decline in number of locations:Yes
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):100
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:It is estimated to number fewer than 5,000 breeding birds (Birt et al. 2012), which are presumed to form one sub-population. Until further data are obtained, an estimate of 5,000 mature individuals is used in this assessment, which is assumed here to equate to c.7,500 individuals in total.

Trend Justification:  A number of colonies have been extirpated by introduced predators and alien invasive species continue to threaten some colonies. A number of other threatening processes are on-going, the combined effects of which are suspected to be causing a moderate decline in this species's global population.

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:5000Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:Yes
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:It nests on steep sea-slopes, canyons and cliffs with a sparse cover of herbaceous and shrubby plants (Drost and Lewis 1995). It is a generalist predator, and may exploit higher prey concentrations around pelagic convergence lines (Hamilton et al. 2004). Nesting persists through mid-June with peak nesting from late March to late April (Jones et al. 2005). Clutches consist of two eggs laid approximately eight days apart with replacement of lost clutches unusual. Incubation takes c. 34 days (Jones et al. 2005).

Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):12.1
Movement patterns:Not a Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): Invasive mammalian predators represent the most important threat to this species. The most significant barrier to its recovery is the presence of invasive cats on Guadalupe Island (B. Tershy in litt. 2007), where they are thought to have caused the extirpation, or at the very least, significantly reduced the population on the main island (Keitt et al. 2006). 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 pollution (Drost and Lewis 1995). Changes in sea temperature associated with global climate change could have an impact on food availability in future (S. Wolf in litt. 2007).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
The most important remaining conservation action is to eradicate cats from Guadalupe Island. Guadalupe Island has been declared a Biosphere Reserve (thanks to Conservación de Islas) (B. Tershy in litt. 1999). The remaining Mexican islands with current or former breeding colonies are either in existing biosphere reserves (Natividad, Asunción 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 fishers (B. Tershy in litt. 1999). A pilot habitat restoration for the species has begun on Santa Barbara Island (Wolf 2008).

Conservation Actions Proposed
Carry out surveys to obtain an up-to-date population estimate. Eradicate cats from Guadalupe Island and ground squirrels from Natividad (B. Tershy in litt. 2007). Develop contingency plans to prevent the establishment of new predator populations (Drost and Lewis 1995). Regulate tourism on Baja California islands (Drost and Lewis 1995). Assess the impact of gill-net fisheries (Drost and Lewis 1995).

Citation: BirdLife International. 2016. Synthliboramphus hypoleucus. The IUCN Red List of Threatened Species 2016: e.T62101215A95187971. . Downloaded on 18 August 2018.
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