Thursday, August 30, 2018

Glaucous-winged x Herring Gulls (?)

I can say with 100% certainty that the birds you are about to see are gulls.  I can even say that they're large white-headed gulls.  Beyond that, well, at some point we cross much more into Wild Ass Guess land than most of the birds that get featured here.

Returning to Juneau, 2 posts ago I ran through as many Glaucous-winged plumages as I could find.  I was trying to get as many portraits of as many individuals and appearances as I could since it'll be a while before I see these birds again, but a lot of the pics don't really fit, and I suspect they're Glaucous-winged x Herring hybrids.

Here's a young bird with an adult Glaucous-winged.
The young bird's bill is barely half the thickness of the adult's, and given the juvie Glaucous-winged from 2 posts ago had a honking thick bill I'm inclined to think this is outside of pure Glaucous-winged.  It's also A LOT paler than most of the one year old (2nd calendar year) birds I saw and its bill is fairly bicolored.  It still has the Glaucous-winged white outer primaries though.

The other young bird it was with also had a narrow bill, though was darker overall both in bill and plumage.
I'm saying its bill is too narrow to not have HERG genes as well.

This next bird is either more advanced and the same age or is a year older with a clearly bi-colored bill.  To me the bi-colored bill screams Herring, but it looks a little heavy headed so I'm putting it here as a possible hybird.

This bird may just be a Herring, though even the extreme ones we see on the Great Lakes aren't usually quite so dark in the wing coverts

Here's a subadult bird.
It has the Glaucous-winged marbling of the head and breast, but the bill is thinner than the adult in the background and it has marked pale-ness to the eye.  Glaucous-winged has dark eyes.

This is a similar bird in flight.
The milky tail and darkish eye look pretty good for Glaucous-winged, but the fresh adult primaries' black tips are at least a shade (and probably two) darker than most of the other adults.

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