Re: Hybrid White-crowned x White-throated Sparrow?


Adam Winer
 

Alvaro,

Thanks for the feedback!  And, yeah, gambeli x Golden-crowned was where I started (and may be where I end).  If nothing else, a few Golden-crowned had just arrived that morning, making it pretty easy to imagine a Golden-crowned hybrid showing up with the same crowd.  It's also a better attested hybrid combo (though there aren't any eBird reports in SF of that combo either). And birdsoftheworld's species accounts make it sound like there's no firm evidence of any White-crowned x White-throated Sparrow hybrid ever having occurred!

What I'll say is that this bird phenotypically matches the things that have previously been called White-crowned x White-throated, and doesn't (to my eye) match the things that have been called White-crowned x Golden-crowned.  Specifically, sorting through Macaulay:


... the "WCSPxWTSP" (in the sense of what people have reported as such, not any absolute statement that they are such):

- Show no golden tones to the crown, whereas all "WCSPxGCSP" do (unsurprisingly! the gold in the crown is probably the first clue that they were looking at a hybrid with GCSP)
- Have very short and thin postocular stripes, whereas most (but not all) of the "WCSPxGCSP" show postocular stripes that connect to black at the back of the neck
- Have fairly thin crown stripes, especially towards the front, with the central white crown stripe coming all the way to the bill, whereas most (but not all) of the "WCSPxGCSP" have fairly broad crown stripes especially towards the bill, with black meeting over the bill.

(I'm not personally noticing any particularly consistent differences between the two buckets in bill or back coloring, though there's clearly variation on both counts.)

I think that the bird in my yard matches each of those characteristics. That doesn't mean, of course, that it *is* a WCSP x WTSP. I may be overvaluing facial pattern, for one;  and also how do I know that some of the claimed WCSP x WTSPs aren't actually WCSP x GCSP? (or, ugh, an F2 backcross - we've already established that backcrosses find their way to my yard!)

At any rate, definitely an interesting bird, and it's fun to try to puzzle this through.

Cheers,
Adam

On Tue, Sep 28, 2021 at 7:21 PM Alvaro Jaramillo <chucao@...> wrote:

Adam

   Amazing looking bird! Hey, if you had sent me this sight unseen with locality/date my thought would have been to call it a Golden-crowned x White-crowned hybrid. The reasons include the overall tone of color above, the noticeable gray wash on breast, the strongly marked crown stripes, long primary projection, and the pink tone to the bill. All suggest a Golden x gambelli White-crowned to me.

Alvaro

 

Alvaro Jaramillo

alvaro@...

www.alvarosadventures.com

 

From: SFBirds@groups.io <SFBirds@groups.io> On Behalf Of Adam Winer
Sent: Tuesday, September 28, 2021 5:52 PM
To: SF Birds <sfbirds@groups.io>
Subject: [SFBirds] Hybrid White-crowned x White-throated Sparrow?

 

Yesterday morning, along with an influx of Golden-crowned Sparrows, I had an odd Zonotrichia in my yard that I'm fairly confident is a hybrid White-crowned x White-throated Sparrow - or, at least, I'm fairly confident is a match for birds others have called that hybrid combo.

 

It's not a very commonly observed hybrid (this would be the first eBird record for San Francisco!), but there are a number of photos from around California and outside, which this bird matches well. (Macaulay Library has quite a few such photos.)

 

Salient features, at least by my eye:

 

- A short and thin black postocular stripe

- Thin crown stripes, with the impression of a pale blob in the lores where a White-throated might have a yellow spot

- A poorly differentiated, but definitely present pale throat and white submoustachial

- A largely pink bill, unlike either the yellow or orange of typical White-crowned ssps for this area

- A rather tan color to the supercilium, neither gray nor white

- Faint streaking on the underparts

 

Neat bird!  But I haven't seen it since.

 

Cheers,

Adam Winer

 

 

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