D50 Archives: Hybrid Gull?

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“Olympic Gull” or Thayer’s Gull? | Stanley Park, Vancouver, BC | February 2013

This week’s “D50 Archives” feature is rather unusual, since I am posting what is likely to be two completely or at least partially separate species: The picture above may be a hybrid gull (in all likelihood an “Olympic Gull,” which is not an actual species, but a cross between a Western and a Glaucous-winged Gull) or it could be a Thayer’s Gull (THGU). I have included below a picture of a Glaucous-winged Gull (GWGU) in its winter plumage – for comparison only, since I will feature at least one other image of this species in a future posting.

I rediscovered the photo above only recently. Looking closely, I noticed right away that the bird’s mantle was darker grey than a pure GWBU, especially the primaries, which are in fact almost black. I also noticed that, compared to the GWGU, its bill looks a bit smaller (compared to its head) and its eye is quite dark. As the image below demonstrates, however, eye colour is not always useful, especially in certain light conditions, since this is clearly a GWBU (with its light grey mantle and primaries), but its eye look quite dark, not clear yellow or light brown as it should be. I should also indicate that the black spot on the bill (next to the red) may also be a sign that a California Gull was involved in creating this individual, but many birders have told me that this indication may be quite misleading, especially in younger adults.

Now I have not always cared much about gulls, especially out in Montreal, because there are relatively few species that are commonly found there and they are readily identified. But on the Pacific coast of North America, nothing could be further from the truth. In fact, many ornithologists here specialize in these birds, given the weird combinations we can find here and the challenge involved in identifying them. So, if you happen to be such an expert, what are your thoughts on the matter?

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Glaucus-winged Gull (non breeding adult) | Stanley Park, Vancouver, BC | March 2013

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