Thursday, November 10, 2016

Winter Sage Sparrow identification redux

Your field guides are useless!

When the former Sage Sparrow was split into two species--Sagebrush and Bell's, one of the several subspecies (canescens) that most thought belonged with Sagebrush, was found to be more genetically similar to Bell's instead. This canescens Bell's Sparrow breeds in central interior California and adjoining central western Nevada. It commonly winters in in the Anza-Borrego desert in the creosote bushes of the Colorado Desert ecoregion. But guess what? So do the Sagebrush Sparrows.

The canescens Bell's sparrow is not shown in any of the standard field guides.

Two winters ago I wrote an identification article on separating winter Sagebrush Sparrows from the canescens form of Bell's Sparrow in far southern California (the ID post is here).

Since I have some recent photos of both to share, I thought I'd write up a little summary again.

ID: The main winter identification separation in the field is that the canescens Bell's Sparrows have heavier dark malars and unstreaked back. The Sagebrush Sparrows have streaked backs and thinner malar stripes. However, there are some birds that have faintly-streaked backs. What are those? Who knows. They go down in eBird as "Sagebrush/Bell's Sparrow (Sage Sparrow)." The back streaking can be hard to see on these active little birds as they run across the sand between the creosote bushes with their tails held high. Thus, eBird reviewers require photographs showing face and back before claiming one or the other definitively.

[Note that both Bell's and Sagebrush Sparrows have streaked wing coverts--paler brown with black center streaks. These streaks on the wing are adjacent to the back, but are not the back streaks.]

January 8, 2017 update: I should point out the experts are still unsure, so perhaps I'm fooling myself thinking I am seeing meaningful differences.

Sagebrush Sparrow
Sagebrush Sparrow (Artemisiospiza nevadensis). Pale brown back with dark streaks. Thin malar. Waste treatment plant, Borrego Springs, California. October 29, 2016. Greg Gillson.
Sagebrush Sparrow
Sagebrush Sparrow. Pale brown back with dark streaks. Thin malar. Old Springs Road Open Space Preserve, Borrego Springs, California. October 30, 2016. Greg Gillson.
Sagebrush Sparrow
Sagebrush Sparrow. Pale brown back with dark streaks. Thin malar. Old Springs Road Open Space Preserve, Borrego Springs, California. October 30, 2016. Greg Gillson.
Bell's Sparrow (canescens)
Bell's Sparrow (Artemisiospiza belli canescens). Unstreaked brown back. Wider malar. Waste treatment plant, Borrego Springs, California. October 29, 2016. Greg Gillson.
Bell's Sparrow (canescens)
Bell's Sparrow. Unstreaked back. Waste treatment plant, Borrego Springs, California. October 29, 2016. Greg Gillson.