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Island Scrub-jay Aphelocoma insularis
BirdLife is updating this factsheet for the 2016 Red List
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This species has been uplisted to Vulnerable because it occupies an extremely small range, being found on only one island, and is susceptible to the arrival of West Nile virus, which has resulted in high mortality in other corvids. This plausible threat could conceivably cause the species to qualify as Critically Endangered or Extinct within one or two generations if adequate intervention is not carried out. Given the limited efficacy of the vaccines available, a stable sub-set of several hundred vaccinated birds would probably be required to safeguard the species from such a fate.

Taxonomic source(s)
AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

33 cm. Smallish, crestless, long-tailed jay, with large bill. Upperparts are predominantly ultramarine-blue; underparts are mostly bluish grey. Female is paler.

Distribution and population
Aphelocoma insularis is endemic to the California Channel Islands, U.S.A., being extant only on Santa Cruz Island (250 km2). Evidence suggests that the species could have been extant on Santa Rosa Island until perhaps the early to mid-20th century (Morrison et al. 2011). The species’s population was previously estimated to number c.9,000 individuals (Rich et al. 2004), of which 7,000 were thought to be breeders (Kelsey and Collins 2000, Rich et al. 2004). However, survey results from 2008 and 2009 suggest there may actually be fewer than 3,000 individuals, and perhaps only c.2,400, probably including fewer than 1,000 breeding pairs, but with no clear evidence of a decline (Morrison et al. 2011, The Nature Conservancy 2011, S. Sillett in litt. 2012).

Population justification
The species's population was previously estimated to number c.9,000 individuals (Rich et al. 2004), including c.7,000 breeders (Kelsey and Collins 2000, Rich et al. 2004). However, the analysis of survey results from 2008 and 2009 suggests there may actually be fewer than 3,000 individuals, and perhaps only c.2,400, probably including fewer than 1,000 breeding pairs (Morrison et al. 2011, The Nature Conservancy 2011, S. Sillett in litt. 2012). Based on this information, the number of mature individuals is estimated at c.2,000.

Trend justification
The population is suspected to be stable in the absence of evidence for any declines or immediate and serious threats.

It occurs throughout nearly all of the woody vegetation on the island, but is especially abundant in canyons and on north facing slopes dominated by Quercus trees.

Very little is known about the species's historic status or ecology; however, there is evidence to suggest that it was lost from Santa Rosa Island in the early to mid-20th century owing at least partly to the impacts of livestock on native vegetation (Morrison et al. 2011). Vegetation on Santa Cruz has been severely degraded by introduced sheep and pigs, but is recovering since their control. It may be susceptible to catastrophic fires and the introduction of diseases. There is particular concern over the potential danger from West Nile virus, which arrived in mainland southern California in 2003, but has not yet become established on Santa Cruz Island (c.30 km from the mainland) (Boyce et al. 2011, Morrison et al. 2011). It is unclear whether this is simply because a vector, most likely an infected bird, has not yet carried the virus to the island or because the climate there is too cool for efficient virus replication in mosquitoes, potentially providing the island’s avifauna with a thermal refuge (Boyce et al. 2011, Morrison et al. 2011). If this latter explanation is correct, it may be only temporary, owing to the potential effects of projected climate change (Morrison et al. 2011). The establishment of West Nile virus on Santa Cruz Island is expected to be catastrophic for the species, assuming a lack of adequate intervention, as it is likely to be at risk of high mortality from the virus, given the lethal impacts in other corvid species (e.g. Kilpatrick et al. 2007, LaDeau et al. 2008). It has been recommended that over 100 individuals in the population be vaccinated each year (Boyce et al. 2011). Climate change may also make the island’s vegetation more susceptible to wildfire. In addition, the species is potentially susceptible to the introduction of rats (Rattus spp.), which are absent from Santa Cruz and Santa Rosa islands, but are extant on three of the other six Channel Islands, having been eradicated from another (Morrison et al. 2011).

Conservation Actions Underway
Conservation action is now controlling introduced sheep and pigs, and in many areas the vegetation is recovering dramatically, but the impact of these ecological changes on the status of this species requires careful monitoring. A programme of vaccination against West Nile virus amongst the population was initiated in 2008 (Morrison et al. 2011), with at least 100 birds vaccinated so far (The Nature Conservancy 2011). However, this is considered a precautionary early measure using a vaccine that has been tested on Western Scrub-jay A. californica with only modest success (Morrison et al. 2011, Wheeler et al. 2011).
Conservation Actions Proposed
Continue to implement a vaccination programme, with the aim of establishing a stable sub-set of several hundred vaccinated birds. Continue to monitor the population for any signs of decline. Eradicate rats from the Channel Islands. Manage the threat of wildfire.

Atwood, J. L.; Collins, C. T. 1997. The Island Scrub-jay: origins, behaviour, and ecology. Birding 29: 476-479.

Boyce, W. M.; Vickers, W.; Morrison, S. A.; Sillett, T. S.; Caldwell, L.; Wheeler, S. S.; Barker, C. M.; Cummings, R.; Reisen, W. K. 2011. Surveillance for West Nile Virus and Vaccination of Free-Ranging Island Scrub-Jays (Aphelocoma insularis) on Santa Cruz Island, California. Vector-Borne and Zoonotic Diseases 11: 1063-1068.

Kelsey, R.; Collins, C. T. 2000. Estimated population size of the Island Scrub-Jay Aphelocoma insularis. Bird Conservation International 10: 137-148.

Kilpatrick, A. M.; LaDeau, S. L.; Marra, P. P. 2007. Ecology of West Nile Virus transmission and its impact on birds in the western hemisphere. The Auk 124(4): 1121-1306.

LaDeau, S. L.; Marra, P. P.; Kilpatrick, A. M.; Calder, C. A. 2008. West Nile Virus revisited: consequences for North American ecology. BioScience 58(10): 937-946.

Morrison, S.A.; Sillett, T. S.; Ghalambor, C. K.; Fitzpatrick, J. W.; Graber, D. M.; Bakker, V. J.; Bowman, R.; Collins, C. T.; Collins, P. W.; Delaney, K. S.; Doak, D. F.; Koenig, W. D.; Laughrin, L.; Lieberman, A. A.; Marzluff, J. M.; Reynolds, M. D.; Scott, J. M.; Stallcup, J. A.; Vickers, W.; Boyce, W. M. 2011. Proactive Conservation Management of an Island-endemic Bird Species in the Face of Global Change. BioScience 61: 1013-1021.

Rich, T.D.; Beardmore, C.J.; Berlanga, H.; Blancher, P.J.; Bradstreet, M.S.W.; Butcher, G.S.; Demarest, D.W.; Dunn, E.H.; Hunter, W.C.; Inigo-Elias, E.E.; Martell, A.M.; Panjabi, A.O.; Pashley, D.N.; Rosenberg, K.V.; Rustay, C.M.; Wendt, J.S.; Will, T.C. 2004. Partners in flight: North American landbird conservation plan. Cornell Lab of Ornithology, Ithaca, NY.

The Nature Conservancy. 2011. No Denial about West Nile: Protecting the Island Scrub-Jay. Available at:

Wheeler, S. S.; Langevin, S.; Woods, L.; Carroll, B. D.; Vickers, W.; Morrison, S. A.; Gwong-Jen J. Chang; Reisen, W. K.; Boyce, W. M. 2011. Efficacy of Three Vaccines in Protecting Western Scrub-Jays (Aphelocoma californica) from Experimental Infection with West Nile Virus: Implications for Vaccination of Island Scrub-Jays (Aphelocoma insularis). Vector-Borne and Zoonotic Diseases 11: 1069-1080.

Further web sources of information
Explore HBW Alive for further information on this species

View photos and videos and hear sounds of this species from the Internet Bird Collection

Text account compilers
Bird, J., Khwaja, N., O'Brien, A., Taylor, J., Wege, D.

Desrosiers, M., Fitzpatrick, J., Langin, K., Morrison, S., Sillett, S., Stallcup, J.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2016) Species factsheet: Aphelocoma insularis. Downloaded from on 21/10/2016. Recommended citation for factsheets for more than one species: BirdLife International (2016) IUCN Red List for birds. Downloaded from on 21/10/2016.

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

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Island scrub-jay (Aphelocoma insularis) 0

Key facts
Current IUCN Red List category Vulnerable
Family Corvidae (Crows and jays)
Species name author Henshaw, 1886
Population size 2000 mature individuals
Population trend Stable
Distribution size (breeding/resident) 250 km2
Country endemic? Yes
Links to further information
- Additional Information on this species