Adult breeding plumage Herring Gull
Gulls. Herring and Ring-billed are pretty simple. They're your everyday "seagull".
But what about the other gulls? Well, Great Black-backed is fairly easy. It's much bigger than anything else. Adult Lesser Black-backed is also fairly simple. It's darker backed than the surrounding Herring Gulls and is bigger than the Ring-bills. What if you added Slaty-backed or Kelp Gull? again, they are much much darker mantled than most of the other gulls you'll see around here. Slaty-backed is dark dark black and Kelp is even darker.
Then what happens if you added Glaucous, Glaucous-winged and Iceland you say. Same thing except backwards. GLGU, GWGU and ICGU are all much lighter in color than Ring-billed or Herring. Neither do they have black primaries which makes ID all the easier.
But what about the tricky ones. Let's try Thayer's Gull. Thayer's Gulls are identical to Herring Gulls in every way, except for three small differences. Adult Thayer's Gulls have dark eyes, no black on the underside of the primaries, and brighter, richer pink legs.
How many times have you picked through a huge flock of gulls at a dump while looking for a Thayer's Gull? Has someone reported a Thayer's minutes ago only for you to miss it? Why is this? Imagine that the other birder has exactly the same skill level you do. He picks out the Thayer's. You can't. Why?
Because if you take into account the variations in plumage and regional plumage variation in both species, you will find that the two species are impossible to tell apart with any certainty.
Now, add a dark Iceland Gull and a light Thayer's Gull. Once again, they are practically impossible to tell apart.
Now think of all the things that to you, constitute a Thayer's Gull.
Bright pink legs? Dark eye? Lack of black on the underside of the primaries? Amount of white on the "windows"?
Then think of all the variations in gull plumage that you've ever seen. Think of all the reports of aberrant gulls and weird looking gulls and darker-backed Herring Gulls, Herring Gulls with a minimal amount of black on the underwing tips......
Taking all that into account, are the field marks that you use to ID a Thayer's Gull really sufficient to actually confidently ID a Thayer's Gull?
I didn't think so.
Ask yourself, do we even know much about Thayer's Gulls? Look at all the other Gulls in North America and then compare to Thayer's. Compared to other gulls, we have very little idea about where Thayer's nest, how they nest, what the incubation period is, what the fledging period is, or even the exact time of year they start nesting. Why is this? Surely not because they nest in remote areas.
You can probably see where this is heading. Ok, I'll get to the point.
SHOULD THAYER'S GULL EVEN BE CONSIDERED A FULL SPECIES?
Should it? But even if we lump it, it doesn't completely solve the ID problem.
If it should be lumped, it would be lumped with ICELAND GULL. This doesn't help us at all.
Now, instead of trying to ID Thayer's vs Iceland, we'll be trying to ID the Thayer's subspecies of Iceland Gull from Herring (which by the way, is considerably harder).
That leaves us back at square one.
So then what about Iceland? Should Iceland be considered a full species? Most people would reply yes. Iceland Gull is considerably easier to ID. Most Icelands are missing the black primaries of Ring-billed and Herring.
So leave Iceland alone.
Let's try lumping another two species. THAYER'S AND HERRING. That would solve all our ID problems. Larus argentatus thayerii would be much easier on us birders than Larus glaucoides thayerii.
Why not? it's easy, it's simple. The two species are identical anyway so why try to ID a bird that you can't ID with any certainty?
Let's hear your thoughts on the subject. Anyone? Post your thoughts in the comments section.
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