Slate-colored fox sparrow


The slate-colored fox sparrow group comprises the Rocky Mountain taxa in the genus Passerella. It is currently classified as a "subspecies group" within the fox sparrows pending a more-thorough genetic assay of all forms.
It has long been suspected to be a separate evolutionary lineage due to morphological distinctness. More recently, it has been split into the present clade and the thick-billed fox sparrow. These have quite similar plumage, but can be readily distinguished according to mtDNA sequence and haplotype data. However, these results were considered tentative until more molecular data and apparent lack of wide-ranging hybridization coupled with ecological differences and adaptations led to confirmation of their distinctiveness ; this group appears to be most closely related to the red fox sparrows, judging from biogeography.
It breeds in relatively short willow habitats in montane regions from the interior of northwest British Columbia to Nevada and eastern California. It is a tiny-billed bird with a gray head and mantle, brown wings, brown breast streaks, and a russet tail.

Subspecies

Like all "fox sparrow" subspecies, it is differentiated into some morphologically recognizable allopatric populations, which are still genetically indistinguishable due to their recent evolution.
However, the handful or so subspecies in this complex are poorly differentiated even morphologically for the most part; a two-subspecies arrangement recognizing the rather distinctive altivagans as distinct from the southern populations might be more reasonable. As with red and sooty fox sparrows, slate-coloreds also prefer to build their nests on the edges of wet habitat but are much less picky about in which plant they build. Their call note is sharp klink according to Rising & Beadle, or "a sharp smack, like Sooty and Red populations" according to Sibley.