Initial deadline for comments: 31 January 2012.
Island Scrub-jay Aphelocoma insularis is endemic to the Channel Islands, California, USA, being extant on Santa Cruz Island, where it inhabits virtually all woody vegetation types. It is listed as Near Threatened under criterion D2, on the basis that it has an extremely small range, being retricted to one location (Extent of Occurrence c.250 km2), but with no known plausible threats that could result in it qualifying as Critically Endangered or Extinct within one or two generations (one generation estimated at c.14.4 years; BirdLife International unpubl. data), although it is considered susceptible to stochastic events in general.
The species’s population was estimated to number c.9,000 mature individuals (Rich et al. 2004), although 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, but with no clear evidence of a decline (Morrison et al. 2011, The Nature Conservancy 2011). It may be susceptible to catastrophic fires and the introduction of diseases, and 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 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). 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).
A programme of vaccination against West Nile virus amongst the Island Scrub-jay 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). Nevertheless, it has been recommended that over 100 individuals in the Island Scrub-jay population be vaccinated each year (Boyce et al. 2011). Given the limited efficacy of the vaccines available (Wheeler et al. 2011), it may be said that until there is a stable sub-set of several hundred vaccinated birds in the population, this plausible threat could conceivably cause the species to qualify as Critically Endangered or Extinct within one or two generations.
For the reasons stated here, the species potentially qualifies for uplisting to Vulnerable under criterion D2. Comments are invited on this potential category change and further information would be welcomed.
Boyce, W. M., Vickers, W., Morrison, S. A., Sillett, T. S., Caldwell, L., Wheeler, S. S., Barker, C. M., Cummings, R. and 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 2011:1063-1068.
Kilpatrick, A. M., LaDeau, S. L. and Marra, P. P. (2007) Ecology of West Nile virus transmission and its impact on birds in the Western Hemisphere. Auk 124: 1121-1136.
LaDeau, S. L., Marra, P. P., Kilpatrick, A. M. and Calder, C. A. (2008) West Nile Virus Revisited: Consequences for North American Ecology. BioScience 58: 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. and 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. and Will, T. C. (2004) Partners in flight: North American landbird conservation plan. Ithaca, NY: Cornell Lab of Ornithology.
The Nature Conservancy (2011) No Denial about West Nile: Protecting the Island Scrub-Jay. http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/california/explore/the-nature-conservancy-in-california-no-denial-about-west-nile-protecti.xml
Wheeler, S. S., Langevin, S., Woods, L., Carroll, B. D., Vickers, W., Morrison, S. A., Gwong-Jen J. Chang, Reisen, W. K. and 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.