[CT Birds] sharp-tailed sparrow (longish)

Mark Szantyr birdinggeek at gmail.com
Sat Feb 9 18:11:38 EST 2013


Thanks Chris ,  An intelligent and well- informed response.  

Mark 

On Feb 8, 2013, at 9:45 PM, Chris Elphick <elphick at sbcglobal.net> wrote:

> 
> 
> 
> 
> Dear all,
> 
> Sorry to chime in so late on this issue - it's been a busy week and like Dave, it seems my kids are on the computer doing homework (really!) constantly.  I wrote Bill about the sharp-tailed sparrow pictures he took at East River this morning and he asked if I would post those comments to the list.  Now that I've found some time to catch up on what has been written by others, I've added a couple of additional things to that original message:
> 
> First, I should say that the East River marsh is, I think, the best place in CT to watch 
> tidal marsh sparrows without getting into the marsh itself.  So, if you want to study them, it's the place to go.
> 
> Regarding the mystery bird, I have 
> emailed with a PhD student in my lab who studies sparrows on the wintering grounds.  She is probably the only active researcher who has 
> daily experience, both of birds in the field and in the hand, with saltmarsh 
> sparrow during summer, fall migration, and winter.  At her winter study sites she 
> routinely catches sharp-taileds that fit all five described subspecies, plus a couple of 
> subspp of seasides - when I was down there last winter, we had all 7 in one morning!   She handles many 100s of sharp-tailed sparrows a year.  
> Her immediate reaction was much like Mark's and mine - that if it's a saltmarsh, 
> it's a strange one.  It's clearly not a typical subvirgatus Nelson's either.  And, I don't think 
> it's a classic nelsonii (though I am much less familiar with that subspecies).  But 
> there's a lot of variation within interior Nelson's, there also is considerable within-population variation across the year due to feather wear, and, of course, there's the issue of 
> hybirds (more on this below).
> 
> Having seen the additional photos, I can see that there is a 
> stronger argument for saltmarsh than initially, but in my view it is far from 
> airtight.  Even if the additional photos look good for saltmarsh, and we can 
> find ways to explain away the apparent plumage discrepancies in the first photo, 
> one still needs to explain the small bill.  Perhaps it's a camera angle issue, 
> but perhaps not.  Bill size does overlap, but it's limited overlap and in my experience when handling birds
> in CT, Nelson's always jump out and it's generally the bill that I notice first.  
> 
> The real problem I see is that (in my view) none of us has a really good handle on 
> the plumage variation within species and within the hybrids - and that variation can only 
> be assessed by studying them on the breeding grounds and/or by studying birds for 
> which genetics confirm the origin.  Consequently, there's nothing to be done 
> with birds that do not fit nicely into either group except speculate.  
> Personally, I lean towards caution in IDs and would just call this a 
> "sharp-tailed" sparrow and move on.
> 
> All is not completely lost.  Along 
> with collaborators in ME, NH, DE and SC we have begun to try to get a handle on 
> the variation.  We systematically photograph all of the birds we capture, score 
> their plumage, take a detailed set of measurements (especially of the bill), and 
> also a DNA sample.  Our colleagues in other states do the same, so that between us we have 
> all this information for birds across the range of saltmarsh sparrow and across 
> the hybrid zone.  A PhD student at the University of New Hampshire has 
> been studying population genetics and hybridization in these birds and can use this information to determine which birds are hybrids. By bringing together the genetics with the photos, plumage scores, and measurements we hope to be able to say just how variable the 
> hybrids can be, and put some limits on which birds can be reliably 
> identified.
> 
> There is a legitimate concern about invoking the "hybrid option" whenever a hard-to-identify bird appears, and in many cases that concern is especially valid.  A lot of odd-looking individuals are just the result of natural variation within species (just look at me!).  But, hybrids in sharp-tailed sparrows are not at all uncommon.  The hybrid zone extends from Mass up into Maine, and at least in some areas a sizable proportion of the population appear to be hybrids. Breeding birds with Nelson's genes have been found as far south as Rhode Island.  Given that the entire world population of saltmarsh sparrows is (we think) only a few 10,000 individuals, the fact that there are almost certainly 100s of hybrids means that the odds of seeing one is quite high.
> 
> So, a long-winded and inconclusive answer to a simple question.  But hopefully 
> useful.
> 
> Cheers,
> 
> Chris
> Chris Elphick
> 
> Storrs, CT
> 
> elphick at sbcglobal.net
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