Synthliboramphus scrippsi 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Charadriiformes Alcidae

Scientific Name: Synthliboramphus scrippsi (Green and Arnold, 1939)
Common Name(s):
English Scripps's Murrelet
Spanish Mérgulo de Scripps
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: 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.

Assessment Information [top]

Red List Category & Criteria: Vulnerable 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., Moreno, R., Sharpe, C.J., Symes, A., Taylor, J., Winnard, S.
This newly split species is listed as Vulnerable because it occupies a small range when breeding, nesting on only a 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 10 locations, the species may warrant downlisting to a lower threat category.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Synthliboramphus scrippsi breeds on islands off southern California, USA (San Miguel, Santa Cruz, Anacapa, Santa Barbara, San Clemente, and, formerly, Santa Catalina) and western Baja California, Mexico (San Benito, and the Coronado and San Jerónimo islands) (Chesser et al. 2012). On large islands the species is confined largely or entirely to offshore rocks (Drost and Lewis 1995). Breeding on San Martín and Cedros islands, Baja California, is uncertain (Chesser et al. 2012). In the USA, an estimated 885-2,575 breeding pairs occur, the biggest colony on the island of Santa Barbara holds 500-1,250 pairs (B. Keitt and D. Whitworth in litt. 2003). 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 (Sowls et al. 1980, Hunt et al. 1981, Carter et al. 1992, Drost and Lewis 1995). The Santa Barbara colony has been stable since the 1980s, but may have declined since the turn of the century (B. Keitt and D. Whitworth in litt. 2003). The species winters offshore from northern California (rarely) south to southern Baja California (Chesser et al. 2012). Some post-breeding birds reach Oregon, USA, and British Columbia, Canada (Gaston and Jones 1998, Karnovsky et al. 2005).

Countries occurrence:
Mexico; United States
Additional data:
Estimated area of occupancy (AOO) - km2:62Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:217000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:6-10Continuing 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:Based on at-sea survey data from 1975 to 2003, Karnovsky et al. (2005) estimate the North American at-sea population of S. hypoleucus/scrippsi to be 39,700, of which 17,900 are thought likely to be mature breeding individuals. Birt et al. (2012) estimate the population of S. (h.) hypoleucus to include fewer than 5,000 breeding birds. On the basis of these data, the population of S. scrippsi is placed in the band for 10,000-19,999 mature individuals, assumed to equate to 15,000-30,000 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:10000-19999Continuing 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). Around Santa Barbara, it feeds on larval fish, especially northern anchovy Engraulis mordax (Hunt and Butler 1980, Hunt et al. 1981). Breeding effort and performance are lower when anchovy abundance is low (Hunt and Butler 1980). Adults enter and leave the nesting colonies at night when there is little or no moon, typically arriving on the Channel Islands in mid-February. 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). There are no recent records of them breeding under shrubs on top of Anacapa Island, a habitat used frequently on nearby, rat-free, Santa Barbara Island (Jones et al. 2005).

Systems:Terrestrial; Marine
Continuing decline in area, extent and/or quality of habitat:No
Generation Length (years):12.1
Movement patterns:Not a Migrant
Congregatory:Congregatory (and dispersive)

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, except Santa Barbara Island (McChesney and Tershy 1998). There was heavy cat predation on North Coronado until the mid-1990s (Jehl and Bond 1975, Drost and Lewis 1995). Black rats Rattus rattus almost extirpated the species from Anacapa (Drost and Lewis 1995), but have now been successfully eradicated (Whitworth et al. 2005). Since the eradication was completed, hatching success has increased three-fold from 30%-85%, and average numbers of nests increased by 14% (Whitworth et al. 2013). More recently Newton et al. 2016 showed 191% more eggs were hatching and 94% less nests were being predated.  House mice were recently introduced to the Coronados Islands and deer mice Peromyscus maniculatus anacapae (native to nearby Cedros Island) have also been introduced to the San Benito Islands. Deer mice predate eggs on Santa Barbara (Murray et al. 1983); however, they were established on Anacapa long before rats were introduced, precluding them from consideration as the cause of declines there (Jones et al. 2006). All breeding colonies in California are legally protected as national parks, private protected areas or military bases. Pollution from offshore oil-wells or the Los Angeles oil-tanker lane could extirpate the species from the south California Bight (Drost and Lewis 1995). 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). 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 future (S. Wolf in litt. 2007).

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 Island (B. Tershy in litt. 1999). 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 (McChesney and Tershy 1998, B. Keitt and D. Whitworth in litt. 2003, Whitworth et al. 2005, Keitt 2005, Aguirre-Muñoz et al. 2008). In 2003, fishing and other extractive uses were 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 threats (S. Wolf in litt. 2007). A pilot habitat restoration for the species has begun on Santa Barbara Island (Wolf 2008).

Conservation Actions Proposed
Eradicate introduced predators on other small islands (Drost and Lewis 1995), including the invasive house mice from Coronados Island and recently introduced deermice from the Western San Benito Island (B. Tershy in litt. 2007). Develop contingency plans to prevent the establishment of new predator populations (Drost and Lewis 1995). Survey remaining potential breeding islands (Drost and Lewis 1995). Continue to monitor population trends with precision (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 scrippsi. The IUCN Red List of Threatened Species 2016: e.T62101249A95188322. . Downloaded on 24 May 2018.
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