Hello, Birders.
I suspect somebody's noticed and commented on this before. And it's basically illustrated and described in the Sibley Guide. But I'd never appreciated it until recently, for what that's worth, so I figured I'd mention it.
In a nutshell: On uncooperative Le Conte's Sparrows flushing from tall grass, the contrast between the dull orange rump and the otherwise gray-brown upperparts is surprisingly conspicuous.
Context: Last weekend, a few birding companions and I were out in far-eastern Colorado, getting our annual fix of tallgrass prairie "vagrants" to the state. (Le Conte's Sparrow, Sprague's Pipit, and perhaps several other tallgrass bird species are considered to be casual in Colorado, but recent field studies indicate that they are regular, maybe even locally fairly common in limited, suitable habitat in the eastern-tier counties of the state.) As we observed the Le Conte's Sparrows out there (at least 6, perhaps 10 or more), I was struck by the following: (1) in all instances, the brevity of the view; (2) the difficulty, in most instances, of making out the "classic" field marks (e.g., the white central crown-stripe or the chestnut-and-gray-streaked nape), and (3) the ease, in all instances, of making out the contrast between the dull orange rump and the otherwise gray-brown upperparts.
This contrast is evident on birds flushing directly away from the observer--basically, your only view if you're dealing with migrants or vagrants in typical tallgrass habitat. On a perched bird, the mark is not evident. (And if the bird is perched for any amount of time, you're, probabilistically speaking, on the breeding grounds, where the bird is singing, and that, as they say, is that.)
The extent of this contrast may vary throughout the year. In particular, I wonder if it's especially prominent on adults that have recently acquired their new (fresh) basic plumage in the fall. The BNA account for Le Conte's Sparrow, by Peter E. Lowther, notes "rump and uppertail-coverts paler than back" in basic plumage, and Sibley notes the "pale orange rump." I definitely agree with "orange," and I also agree with "paler," but I think "orange" is more important than "pale[r]," as that color really stands out from the gray-brown ("dark gray," according to BNA) upperparts.
(Kenn Kaufman has a useful reminder in the January 2009 Birding, p. 11, regarding difference between sparrows on the breeding grounds vs. off the breeding grounds. "Birders...may be stunned to see how much more brightly and crisply marked [sparrows] are in early winter than in mid-summer. Their plumage is still fresh and new in early winter, but by mid-summer it can be quite worn and faded. The effects of wear are seldom discussed or illustrated in field guides...")
Bryan Patrick got a photo of one of these Le Conte's Sparrows in the act of flushing, and the photo is both "terrible" and "excellent." Terrible in the sense that it could be a dipper, a diving-petrel, or an Ivorybill. Excellent, though, because you can clearly see the orange rump contrasting with the gray-brown blur of a bird, or stone, or thumbprint, or whatever it is.
One other observation. The flushing Le Conte's never, ever, uttered a peep. In contrast, the Grasshopper Sparrows out there gave a few flight calls, and the Savannah Sparrows gave a lot of flight calls. (In Colorado, the congeneric Grasshopper Sparrow is an obvious point of possible confusion with Le Conte's Sparrow. I believe the short-tailed, variable, sometimes-quite-furtive Savannah Sparrow is also a possible point of confusion.)
To sum it up: Le Conte's Sparrows, when flushed from tall grass, show a conspicuous orange rump; this mark may be especially prominent on adults in fresh basic plumage; and flushing Le Conte's Sparrows may be relatively quiet (compared to, say, Savannah Sparrow or Sedge Wren).
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Ted Floyd
tedfloyd57@...
Lafayette, Boulder County, Colorado
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Ted Floyd
Editor, Birding
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