Pica nutalli (del Hoyo and Collar 2016) was previously listed as P. nuttalli.
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
|2000||Lower Risk/Least Concern|
|1994||Lower Risk/Least Concern|
|1988||Lower Risk/Least Concern|
|Migratory status||not a migrant||Forest dependency||Low|
|Land mass type||Average mass||-|
|Extent of Occurrence breeding/resident (km2)||105,000||medium|
|Number of locations||-|
|Value||Data quality||Derivation||Year of estimate|
|No. of mature individuals||50000-99999||poor||estimated||2014|
|Decline (3 years/1 generation past)||-||-||-|
|Decline (5 years/1 generation past)||-||-||-|
|Decline (10 years/1 generation past)||-||-||-|
|Decline (10 years/3 generation future)||-||-||-|
|Decline (10 years/3 generation past and future)||-||-||-|
|Number of subpopulations||-||-||-|
|Percentage in largest subpopulation||-||-||-|
|Generation length (yrs)||7.1||-||-||-|
Population justification: The species's population was estimated at c.180,000 individuals in 2003, but is thought to have been reduced by 49% by 2006 (del Hoyo et al. 2009) owing to West Nile Virus. Partners in Flight estimate the population to be 90,000 individuals (Partners in Flight Science Committee 2013). The population now appears to have stopped its decline and may have recovered somewhat (W. Koenig in litt. 2016), thus the population is placed in the band for 50,000-99,999 mature individuals, which is assumed to equate to c.75,000-150,000 individuals in total.
Trend justification: The species suffered high levels of mortality and a severe population decline owing to an outbreak of West Nile virus (Airola et al. 2007, Crosbie et al. 2008). Following the documented arrival of the virus in California in summer 2003 (Reisen et al. 2004), data have suggested a decline of 42-49% from 2004 to 2006 (Crosbie et al. 2008). Christmas Bird Count (CBC) data from the Lower Sacramento Valley suggest that numbers of this species declined by 48% between 2004/2005 and 2005/2006, with surveyed numbers in 2005/2006 having declined by 38% compared to the previous 10-year average when accounting for the effects of bad weather (Airola et al. 2007). The population appeared to reach a low in 2007-2008, and since then has shown signs of recovery, although it was still depleted in 2010/2011 compared to data collected since the late 1950s (W. Koenig in litt. 2012).
Year by year records from Sauer et al. (2017) show that the species may have continued to decline since the end of the West Nile Virus outbreak, although the decline is deemed non-significant, and instead the species may be considered to be stable. Using the year by year records also means that we can track back to three generations ago (1997) and calculate the population reduction up to 2015. Sauer et al. (2017) show that between 1997 and 2015, the average annual decline was 4.92% (3.00-6.92%), although of course the majority of this was concentrated during the West Nile Virus outbreak. Assuming population stability between 2015 and 2018 would still give a population reduction of 59.7% (42.2-72.5%) over the past three generations.
|Habitat (level 1)||Habitat (level 2)||Importance||Occurrence|
|Altitude||Occasional altitudinal limits|
|Threat (level 1)||Threat (level 2)||Impact and Stresses|
|Agriculture & aquaculture||Annual & perennial non-timber crops - Agro-industry farming||Timing||Scope||Severity||Impact|
|Climate change & severe weather||Droughts||Timing||Scope||Severity||Impact|
|Past, Likely to Return||Majority (50-90%)||Causing/Could cause fluctuations||Past Impact|
|Invasive and other problematic species, genes & diseases||Viral/prion-induced diseases - West Nile Virus (WNV)||Timing||Scope||Severity||Impact|
|Past, Unlikely to Return||Whole (>90%)||Rapid Declines||Past Impact|
|Pollution||Agricultural & forestry effluents - Herbicides and pesticides||Timing||Scope||Severity||Impact|
|Residential & commercial development||Housing & urban areas||Timing||Scope||Severity||Impact|
|Purpose||Primary form used||Life stage used||Source||Scale||Level||Timing|
|Pets/display animals, horticulture||-||-||-||International||Non-trivial||Recent|
|Pets/display animals, horticulture||-||-||International||Non-trivial||Recent|
BirdLife International (2021) Species factsheet: Pica nutalli. Downloaded from http://www.birdlife.org on 23/04/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/04/2021.