Separating Sagebrush Sparrow and Bell's Sparrow
Looks difficult.
Peter Pyle 2013, https://www.sibleyguides.com/wp-content/uploads/On-separating-Sagebrush-and-Bells-Sparrows.pdf
Sagebrush Sparrow (A. nevadensis, formerly A. belli nevadensis) was elevated to species by AOU in 2013 from Bell's Sparrow (A. belli) and its subordinate subspecies, A. b. canescens (near A. nevadensis), A. b. belli, A. b. cinerea, and A. b. clementae.
It appears that A. nevadensis and A. b. canescens may be most difficult to separate in winter when the ranges of worn individuals overlap.
