Species

Justification
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population is declining only slowly, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern. The long term impact of West Nile virus on the population is being monitored, and if the population is found to be declining more rapidly than currently thought, it will warrant uplisting to a higher threat category.

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.

Trend justification
Over the last 40 years of the 20th century, the population of this species was stable (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). However, with the documented arrival of West Nile virus in California in summer 2003 (Reisen et al. 2004) the species suffered high levels of mortality and a severe population decline owing to a high susceptibility to the virus (Airola et al. 2007, Crosbie et al. 2008). Data suggests a decline of 42-49% from 2004 to 2006 (Crosbie et al. 2008) and alternative Christmas Bird Count (CBC) data from the Lower Sacramento Valley suggests that numbers have declined by c. 48% between 2004/2005 and 2005/2006, with surveyed numbers in 2005/2006 having declined by c. 38% compared to the previous 10-year average after accounting for the effects of bad weather (Airola et al. 2007). The population decline appeared to peak in 2007-2008, and since then the population appears to have recovered somewhat (W. Koenig in litt. 2012). Despite this recent decline, the long-term population trend appears positive, with analysis of CBC data by Airola et al. (2007) showing that the species had been increasing on average between 1980/1981 and 2001/2002. Further information is needed to determine the magnitude of the suspected decline.

Threats
Yellow-billed magpie numbers in California may be declining due to habitat loss/conversion, rodent poisoning, and West Nile virus (Airola et al. 2007, Crosbie et al. 2008).

References
Butcher, G.S. and Niven, D.K. 2007. Combining data from the Christmas Bird Count and the Breeding Bird Survey to determine the continental status and trends of North American birds. National Audobon Society, New York, USA.

Reisen, W.; Lothrop, H.; Chiles, R.; Madon, M.; Cossen, C.; Woods, L.; Husted, S.; Kramer, V.; Edman, J. 2004. West Nile Virus in California. . Emerging and Infectuous Diseases 10: 1369-1378.

Further web sources of information
Hear sounds for this species from xeno-canto, the community database of shared bird sounds from around the world.

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

Text account compilers
Butchart, S., Derhé, M., Ekstrom, J., Sharpe, C J

Contributors
Koenig, W.

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

Recommended citation
BirdLife International (2013) Species factsheet: Pica nuttalli. Downloaded from http://www.birdlife.org on 22/05/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/05/2013.

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.

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