Saturday, February 23, 2013

first cycle Slaty-backed Gull in CT?

 [Feb 25 update: We have received correspondence from a couple of authoritative larophiles from other continents with SBGU experience. Both have stated that this could very well be a good Slaty-backed Gull but there are some concerns, with leg color and structure being mentioned most often. No deal-breakers though. Other possibilities include a very atypical smithsonianus HERG or a hybrid of New or Old World species. As one of them put it "it certainly looks so similar [to SBGU] that it would be worrying if it is something else entirely!"

The bad news is that we're no closer to knowing what this bird is. The good news is that their concerns echo our own, which shows that most of us seem to be on the same page here.

If anything new develops I will update this post again.]

A few days ago Mark Szantyr found an interesting first cycle gull at the Windsor Landfill that seems like a decent candidate for Slaty-backed Gull. I carpooled to the fill this morning with Julian Hough and Jake Musser to find a small group of birders already working the flock. After a bit of time we located Mark's gull and studied/photo'd it until it started to get uncomfortably wet.

All photos below are completely unedited except for cropping. Conditions were overcast with a light mist/drizzle. Click thumbnail for larger image. Take a look at all the photos as size, structure, and even plumage features seemingly vary from photo to photo.

I'm going to leave the comments to a minimum here, at least for now. The question here is, how identifiable is a first cycle Slaty-backed Gull in North America? Can it be done with confidence? If so, does this bird fit the bill? For example, can a worn, faded smithsonianus Herring Gull or hybrid be ruled out?

If you have any thoughts, please feel free to use the Comments section at the end of the post. I will likely respond by playing devil's advocate in either direction :-) Otherwise, enjoy this head-scratcher. Bigtime kudos to Mark for picking out this bird and bringing it to our attention.

marked by arrow, to give a feel for how it looked among the flock

center, body facing away, head turned right

center, in profile

wings raised

center, facing us


with first cycle GBBG behind

from left: GBBG, subject bird, HERG, HERG


facing left, with GBBG behind, HERG at far right



Of the two young birds here, the subject bird is on the left, and a first cycle HERG is to its right








among Herring Gulls






subject on left, HERG on the right















I currently do not have an opinion on this bird (and I'm not alone). Much more research is needed, all of which could be for naught; this one may go unidentified. I personally have seen zero SBGU of this age. On the other hand, I have seen thousands of first cycle Herring Gulls, and we know how ridiculously variable HERG and HERG hybrids can be...

Check out images of the same bird by Mark Szantyr, Julian Hough, and Joseph Cala so you can get a feel for what it looks like under different conditions/cameras/edits.

 - NB

7 comments:

  1. Of the over 60 or so records of SBGU that the CA committee has accepted, only two are first year birds. Two records of first year birds have been rejected as well, although I dont know on what grounds. I don't think it is an impossible plumage to ID here, although its obviously tricky...I'm sure its more straightforward in parts of Alaska.

    I think those dark mantle feathers coming in, among a number of other field marks, eliminate a pure Smithsonianus...but Im not very well versed on HERG X black-backed gull hybirds.

    Anything blatantly "wrong" for SBGU on this bird?

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  2. Hi Steve. Thanks for that. I have seen the occasional first cycle HERG that has seemed to show a similar mid-gray cast to first winter scapulars, but these birds have otherwise looked fine for HERGs, so I've just called them that and moved on (perhaps in error?). So I'm not sure that rules HERG out.

    I haven't yet noticed anything blatantly off for SBGU, but my research of minutiae such as exact feather patterning is in the beginning stages. I hope to delve deeper into this over the coming week. If I find something wrong, I'll mention it. So far, of the handful of experienced gullers that have seen photos, nobody has mentioned any deal-breakers for SBGU.

    I would feel better if the leg color was deeper pink, but this is variable, especially in first year birds. Perhaps not a deal-breaker.

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  3. In these photographs, some of those new gray scap feathers appear extremely dark (too dark for Smithsonianus, IMHO), but since you saw the bird in person I'm sure you have a better sense of their true color.

    Keep us updated!

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  4. Nick,

    Despite all the caveats you and I have discussed in private, I am feeling better about this bird and less inclined to feel it's a weird smithsonianus, since the sum of its parts don't add up to that taxon and fit SBGU better. The actual width of the dark secondary bar, the upperwing pattern, the shape of the internal markings on the scaps as well as the perceived their darkness seem pro-SBGU. The tail pattern also seems to be SBG-like more than smithsonianus too. The barring that is quite extensive on the inner webs of the outer tail feathers isn't what I'd expect mpared to a smithsonianus. They tend to show barring restricted to the bases of the outer two feathers and a little ways down the outer web of the outer tail.Of course we can find variation to dispute what i just sa if we look hard enough, but that it matches SBGU is good. The underpart markings and the pattern of the undertail coverts seem also to fit SBGU better than smithsonianus. Bill seems spot-on for SBGU, wth that fleshy base starting to develop. Structurally it is interesting that in photos it has that unbalanced look to it with a pot-belly. I don't see too much wrong structurally and in some flight shots, it has that broad-backed look. So, if I had to commit some comments, these are them. I don't see anything too off for SBGU.

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  5. Julian, I agree that it's difficult to find anything wrong for SBGU with this bird, with everything falling somewhere into the range of variation for that species. But in this case that might not be enough. If this bird had deep pink legs and a slightly shorter-winged look to it (though I think it looks short winged in some photos, longer in other), I think we'd have enough to slap a name to it. Given what we know right now, I think a bird textbook in every way is needed. Frustrating though. I don't think this bird is smithsonianus, but can I even be sure of that?

    I have updated the post at the top with the most recent developments.

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  6. Hi Nick and Julian.

    Peter Pyle has made a comment on the age of this gull, in which hi suggest that it might even be a second cycle bird? The pointed primaries and and juvenile tertials among other plumage features suggest the oposite - namely a first cycle.

    JanJ

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  7. Thanks JanJ,

    After further correspondence I believe that everyone now agrees this is a first cycle bird, but it was right to rule out second cycle as that would have changed our perspective.

    Interesting bird that will likely never be definitively ID'd. One of the most telling stories is of a well respected birder who identified the bird differently based on two different photo sets.

    As for me, I still think that SBGU is in play but perhaps not even smithsonianus can be ruled out here, nevermind hybrids. It would take some hard evidence for me to put a name to this thing.

    Thanks everyone for the comments thusfar. This bird has stirred a healthy debate.

    ReplyDelete