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 other young bird it was with also had a narrow bill, though was darker overall both in bill and plumage.
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.
This is a similar bird in flight.