Like all "fox sparrow" subspecies, it is differentiated into some morphologically recognizable allopatric populations, which are still genetically indistinguishable due to their recent evolution (Zink 1994).
However, the handful or so of subspecies in this complex are poorly differentiated even morphologically for the most part; a two-subspecies arrangement recognizing the rather distinctive altivagans (the northern form) as distinct from the southern populations (schistacea) might be more reasonable (Rising & Beadle 1996). 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 a sharp klink according to Rising & Beadle (1996), or "a sharp smack, like Sooty and Red populations" according to Sibley (2000).
Not defined by the ICZN /wiki/International_Code_of_Zoological_Nomenclature ↩