Sunday, October 18, 2015

Gambling on a Gambel's Sparrow

Yesterday I was helping band birds with Natalia out at a beautiful Piedmont Prairie restoration site near the Uwharrie National Forest, when we caught a White-crowed Sparrow.

White-crownes aren't all that common in North Carolina, so getting to catch and handle one was an exciting diversion from the hordes of Song and Field Sparrows. But something about this bird made it a little bit extra special:

White-crowned Sparrow
Can you see it?

The lores (space between the eye and bill) are pale, when they -should- be filled with a black line connecting the black of the broken eye ring to the black crown stripe at the base of the upper mandible. At least that's how birds in the east, belonging to the nominate subspecies, leucophrys, are supposed to look.

Here's an example of a typical eastern adult.

Sibley illustrates this difference in his Second Edition and provides some detailed commentary about the five subspecies on his website: http://www.sibleyguides.com/bird-info/white-crowned-sparrow/

The bird we caught looks like a good candidate for the Western Taiga (Gambel's) White-crowned Sparrow, which might be a rare find in North Carolina. The Birds of North Carolina: their Distribution and Abundance website lists just two prior records: a specimen collected from the mountains in late Oct. 1932, and a report of one at a feeder near the coast on the odd date (for an overwintering species) of July 14, 2007.

But a quick perusal of the Carolina Bird Club photo gallery turns up several examples of birds that might make decent Gambel's, or at least east-west intergrade, candidates.  See here, here, here, here, and here.

Sibley, further discusses the distribution of winter subspecies and observes that pale-lored White-crowns are found in the east far more frequently than we should expect given what we know about the north-south orientation of Gambel's migration. He laments that... "it just doesn’t seem like these birds should show up in the east more often than, say, Harris’s Sparrow."

North Carolina has 9 records of Harris's Sparrow.  How many Gambel's-looking White-crowned Sparrow records would their be if birders were looking out for them and reporting them?

Some of the comments below Sibley's post suggest that up to 10% of wintering White-crowns appear to be Gambel's type in Southern New England, so perhaps the little sparrow we caught isn't quite so unexpected.




If we take a closer look at those lores, you can just make out a hint of blackness to the feathering.






OK.  How about an even closer look.





Could this bird be from the intergrade zone between leucophrys and gambeli?


This bird wintering in Los Angeles certainly seems to lack even this hint of black and is probably a good standard for 'pure' gambeli.

Gambel's White-crowned Sparrow, Los Angeles, CA
Heck the front of the eye ring isn't even broken and the bill looks way more yellow-orange (rather than pink-orange).

Wherever the bird we caught came from and whatever subspecies to which it may belong, it's fun to discover that there's still so much we don't understand about relatively common and well-known North American birds.


What do you think of this bird?  Would you bet on Gambeli? Third North Carolina report?

7 comments:

  1. Greetings. You make no reference to "The Pyle Guide, part 1" which should be present at all banding stations. Sibley's work offers important details which can be helpful in the identification of sub-species in the field, but in the hand, Sibley's work is, at best, a secondary reference. Indeed, Pyle relegates the "upper lore" color when considering WCSP sub-species to the 5th listed factor after overall size, bill length, wing morphology and upper parts color. Pyle, p. 590.

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    Replies
    1. Thanks for this comment.
      Certainly those other features are more important in California where there are three pale-lored subspecies to sort through!
      I don't have Pyle in front me, but you're probably right... it would have been worth taking some measurements to confirm their consistency with gambelii.

      Delete
  2. That bird from Los Angeles seems more like a pugetensis or nuttalli rather than a gambelii.

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    Replies
    1. Hi Matt,

      What makes you think pugetensis or nuttalli?

      I'm certainly no expert in the California subspecies and could be missing something, but based on what I can easily find on Google, I have to disagree.

      Pugetensis should have a different back pattern with black centers and tan edges. The LA bird has deep reddish centers with pale gray edges.

      Nuttalli should look darker. Furthermore, it doesn't leave the immediate coast whereas this bird was photographed up in the San Gabriel Mountains.

      Delete
    2. The bill looks yellow to me, which always jumped out to me as the most obvious difference. Agree that the back pattern seems more like a Gambel's.

      Delete
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