Monday, January 11, 2010

Mystery Gull

Below are several photos taken January 8th from the sewage outflow in St. John's Newfoundland. In general size this bird is between average Iceland and Herring Gull. The bill in particular stands out among surrounding Iceland Gull and seems closer to Herring Gull in size.

I have already received several comments on this bird. Most people advising this is a Thayer's Gull.Another commented that it could be some kind of Herring Gull hybrid.It surely cannot be a Kumlien's Iceland Gull.

What confuses me about this bird is large amount of black in the wing tips. I have searched the internet and cannot find a Thayer's Gull with this amount of black in the primaries. I guess it's possible that some might consider Herring Gull in this identification,but this gull very clearly has a purple/pink orbital ring,that is never seen in Herring Gull to my knowledge.

Thayer's Gull is very rare in Newfoundland,the extreme variation in our Iceland Gulls makes it difficult to know where to draw the line between Thayer's and Kumliens(for me at least).

My question is,can this bird be unequivocally identified as Thayer's Gull? If not,then What is it? Could an Herring X Iceland Gull or Herring X Thayer's look like this? Again,to my knowledge neither of these crosses have been documented.

Any comments would be greatly appreciated and photos of similar looking Thayer's Gull would be excellent.









3 comments:

  1. This gull does not look good at all for Thayer's. In particular, the underside of the outer primries have too much black showing through (Thayer's Gull looks more silvery), plus there is way too much black in the outer primaries for Thayer's which has a neater and much more limited trim of black on each of the outer primaries.

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  2. Dave - I think that the underside wingtip pattern is fine for Thayer's, at least as far as extent and darkness on the outer few primaries -- the only black is the tips of the outer 4-5. However, though I cannot be sure due to the views provided, the number of primaries with straps seems on the short side, more like Iceland; Thayer's usually shows a strap on p5. I think.

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  3. Tony's mention of a "strap" on P5 is the telltale mark that would distinguish Thayer's from Iceland. Although, not every Thayer's shows a subterminal band on P5. If this bird had a full band then we would eliminate Iceland. The lack of a band on P5 does not, however, eliminate Thayer's.

    Jake, there are specimens of Thayer's Gulls with an unusual amount of black in the wingtips and underwing (albeit an atypical pattern for this taxon). See the last two skins of the adult Thayer's below:

    http://www.freewebs.com/merseybirders/gullidentificationpage.htm

    I would leave this bird as a Thayer's/Iceland type. In the close-up shots the bill looks big and better for Thayer's. However, in the first photo, the bill looks okay for Iceland. Eye color is not much to work with here. The markings on the neck/hindneck seem better for Thayer's. An interesting bird to say the least.

    Amar Ayyash
    Illinois, USA

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