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Herring Aids

December 6, 2007

I went into the museum this week to get some pictures of the mystery gulls I mentioned in my last museum post. But first we had business to take care of with the Massachusetts Bird Records Committee. See, apparently a Pterodroma type petrel was seen off the coast of Massachusetts a few years back. They are almost certain it’s a Black-capped Petrel but they wanted to look at some skins to get an idea of the variation within the species.

At the NC Museum of Natural Sciences, we have loads of Black-capped Petrels, as you can see to the left. So first we picked a few birds from roundabout when the MA bird was seen and took some photos to send to the good folks up north.

That done, I went back to finish up the Herring Gulls and, in doing so, wrap up my excursion into the family Laridae. Not much going for the birds I had left, let’s go straight to the birds I identified originally as Yellow-legged Gulls (Larus michahellis). I’ve got some additional pictures that may shed a little light on the subject. First here’s the presumed michahellis (bottom) side by side with an European Herring Gull (Larus argentatus) (top) also in the collection. You can see the slightly lighter mantle in the bottom bird, consistent with Yellow-legged Gull but not entirely conclusive. (edit to add: actually this isn’t nearly as conclusive as I originally though, and I got them mixed up. YL should be darker. That throws quite the monkey wrench into my predicament)

This next picture shows the wingtip to the best I was able to display it. I’m not totally familiar with the differences between michahellis and argentatus here, though I know michahellis shows a darker wingtip but I don’t have experience with either bird personally and the Howell/Dunn book doesn’t show the wings in a way in which I can readily compare them. Any takers out there willing to go out on a limb with this guy? Are my two birds Yellow-legged Gulls or two weird yellow-legged European Herring Gulls?

  1. slybird permalink
    December 6, 2007 9:46 am

    Well for starters, every reference I have says michahellis should be the darker bird… am I reading something wrong? I’m inconclusive on the wing-tip pattern but lean slightly herring.

  2. slybird permalink
    December 6, 2007 9:47 am

    Darker bird in terms of mantle color, I mean.

  3. December 6, 2007 9:56 am

    Hmm, you’re right. I don’t know why I hadn’t noted that, for whatever reason I thought it was the other way around.

    The argentatus is an fair bit older skin which tend to be darker so that could have something to do with it. Also I believe European Herring is darker than American.

    I actually tend to agree with you on the wingtips.

  4. slybird permalink
    December 6, 2007 10:07 am

    I think what you really need is some european opinions… why not post on birdforum? Or ID-Frontiers?

    The darker-mantled bird also has darker black wingtips… hmm are you sure you remember which one is which? 🙂

  5. December 6, 2007 1:43 pm

    No the birds are correct. I may post to ID-Frontiers, they’re pretty good about that stuff…

  6. Jochen permalink
    December 8, 2007 9:43 am

    Sorry, I have very little time at the moment, so I can’t comment in detail until January, you’ll see why soon on my blog.
    Posting the gulls on ID frontiers is a good plan!

  7. January 4, 2009 12:57 pm

    Just to put a bookend on these birds way way way after the fact.

    Based on the wingtip, they’re most definitely argentatus, or in english, European Herring Gulls. They’re both odd individuals with yellow legs which is probably what made them targets for collection.

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