The challenge of separating Bell’s Sparrow and Sagebrush Sparrow

1/3/2017 | 0

Sagebrush Sparrow near Phoenix, Arizona, January 2015, by Laure Wilson Neish.

Sagebrush Sparrow near Phoenix, Arizona, January 2015, by Laure Wilson Neish.

Kenn Kaufman’s column “ID Tips” appears in every issue of BirdWatching. In our January-February 2017 issue, he takes on the challenging task of separating Sagebrush Sparrow and Bell’s Sparrow, a pair of species known as Sage Sparrow until not too long ago. But even then, writes Kenn, birders struggled with differences between the darker coastal form and paler interior birds:

Although the official split of Bell’s Sparrow and Sagebrush Sparrow happened just in 2013, the forms have been the subject of controversy and confusion for years. As long ago as the 1890s, Joseph Grinnell struggled to figure out the status of the birds in southern California. He eventually described the paler sparrows of the Mojave Desert as the subspecies canescens, but he assumed that they were most closely related to the widespread form of the Great Basin, subspecies nevadensis.

That was a logical assumption, too, based on overall similarity. At a glance, the darker birds of the coastal regions seem distinctly different from the more pallid birds of the dry country of the interior. But superficial appearance isn’t the deciding factor. Detailed analysis of DNA has shown conclusively that canescens is genetically closer to the dark Bell’s Sparrow types of the coast, and slightly more distinct from its very similar neighbors to the east.

Humans have been attempting to classify birds for centuries, but until recently, attempts have relied on visible similarities. In this new era, looking from the standpoint of genetics, we’ve been treated to one surprise after another. Some involve major shifts, like learning that falcons and hawks are not related. But even small surprises, like the relationships of these dry-country sparrows, give us reason to look at birds more closely, and that’s always a good thing. — Kenn Kaufman

Kenn Kaufman’s “ID Tips,” featuring the photographs of Brian E. Small, appears in every issue of BirdWatching. A version of this article appears in our January-February 2017 issue, which will go on sale at Barnes & Noble and other newsstands January 10.

Read other articles by and about Kenn Kaufman.

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