eWestern Birds

Abundance and Distribution of the Yellow-billed Magpie

Scott P. Crosbie, Levi E. Souza, and Holly B. Ernest

ABSTRACT: In 2007 and 2008, we evaluated the distribution of the Yellow-billed Magpie (Pica nuttalli) and estimated habitat-specific densities and abundances with point-transect surveys. We found possible contractions since the mid-20th century, with reductions from Fresno south to Bakersfield, in the Sacramento delta, and in southern portions of the Coast Ranges of central California. Over the species’ entire range, its population density was 6.1 birds/km² and approximately 4.0 × 10⁵ birds (percent coefficient of variation [%CV] 13.1%). Density was greatest in agricultural habitats (8.2 birds/km², 17.4% CV) and least in urban habitats (1.3 birds/km², 36.9% CV). Abundance was greatest in rural habitats (2.5 × 10⁵ birds, 17.0% CV) and least in urban habitats (5.3 × 10³ birds). Further monitoring of temporal trends in the abundance of this bird endemic to central California and studies of its population genetics, habitat usage, and demography are warranted.

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