[Mystery bird] Field Sparrow, Spizella pusilla, photographed at Newton Hills State Park in South Dakota. [I will identify this bird for you tomorrow]
Image: Terry Sohl, 30 September 2008 [larger view].
Photo taken with Canon 40D, 400 5.6L.
Please name at least one field mark that supports your identification.
Rick Wright, Managing Director of WINGS Birding Tours Worldwide, writes:
The identification of sparrows got a lot easier in 1990, when Kenn Kaufman’s Advanced Birding codified what he calls “the generic approach.” Rather than focusing on the pattern of the underparts or in the first instance on the precise details of the head plumage, we know now to first gauge the bird’s size, structure, and shape, a procedure that helps us reduce the possibilities from an often overwhelming 40 or more brown birds to just a handful.
Only sumacs have buds wholly encircled by leaf scars, so we know that this bird is perched in a Rhus. That gives us a nice yardstick: we’re looking at a small sparrow. Starting at the rear, we notice a markedly long, rather narrow tail. A similar slenderness characterizes the entire bird; this is not one of the big pot-bellied sparrows, and the head seems just a bit too small for the body.
A small, slender sparrow with a long tail and small head is a Spizella, a member of the genus including such familiar species as Chipping Sparrow. If I remember rightly, Kaufman’s Advanced Birding (I can’t recommend this book often enough or highly enough!) devotes an entire chapter to dull winter Spizella, but happily enough, our quiz bird is a bright individual of a distinctive species.
The silvery rump and bright wing let us exclude Clay-colored and Brewer’s Sparrows (and Black-chinned was never really in the running, was it?). Chipping and American Tree Sparrows are much more richly colored on the mantle. And the mystery bird’s head pattern is distinctive: a dull rufous crown with a poorly defined central crown stripe, a huge gray supercilium separated from the gray auriculars by a dull rufous postocular, and a crisp eyering combining with pale lores to give the bird an “open,” “friendly,” “sweet,” “innocent” expression. The bright pink bill confirms our identification as Field Sparrow, the only bird that combines these characters.
Or almost the only bird. Worthen’s Sparrow is a rare and little-known Mexican bird that closely resembles Field Sparrow in all its plumages (in fact, the first Worthen’s Sparrow ever collected [in New Mexico!] was first identified as a badly out-of-range field sparrow). I suspect that a good birding botanist could rule Worthern’s out on the basis of the sumac species here, but there’s another, quicker way: Worthen’s Sparrow has dark tarsi and toes, while our bird shows the typical pinkish feet of a Field Sparrow.