1) Poor view, 2) unfamiliar with local abundance or seasonal occurrence, 3) unfamiliar with all plumages or variation, 4) over-eager to see a rarity. These are all reasons why an identification error might occur, why one might mistake a common bird for some rarity.

One can even mistake one common species for another. That usually comes from relying too much on a single "diagnostic" field mark. And what have I been trying to teach with my ID Quizzes? "The purpose of these quizzes is to learn to identify the whole_bird."

So, in this quiz I present the most misidentified bird in western North America.*

Here is how one might make approach identifying this bird: This obvious gull has a yellow bill with black ring around the tip. The legs are yellowish. There are only three choices, Mew with unmarked bill, California with a red and black spot on the bill, and Ring-billed with a black ring around the bill. This has to be a Ring-billed Gull. Easy.

And wrong.

The above logic is unassailable--unless, of course, the bird is not an adult.

Now, I know from experience that 99.7% (997 out of 1000) of you don't want me to go into a long involved discussion of gull aging and molt. Just remember this easy 1-2-3 gull aging sequence: 1) back, 2) wing coverts, 3) wing tips.

Gulls start as tan and brown marked juveniles with brownish wing tips. Depending upon species they take 2-4 years to molt into adult plumage. The brown and tan juvenile first gets an adult-like gray back. Next, the wing coverts become an adult-like gray. Finally, the brown wing tips become black (except the "white-winged" gulls such as Glaucous, etc.) with white windows.

Looking again at the quiz bird we can see that this bird has very worn but solid brown wing tips, and mostly gray back and wing coverts. There are a few frayed and worn brown feathers in the wing coverts, but most are gray. The next time this bird completes its fall molt it will be an adult. But it is not an adult yet.

In this last plumage before reaching adult plumage the eye usually reaches the adult color, the legs are close to adult color, and the bill is yellowish with a dark tip, often ringed. In other words, a ringed bill is common in most large gulls the year before reaching adult plumage.

In the plumage just before adult plumage the legs and eye are very close to the adult color, The bill color doesn't mean much, but the bill shape is helpful. So, look again. The legs are greenish yellow. They eye is very dark. The bill is fairly long and straight.

Greenish-yellow legs eliminate all North American gulls except Mew, Ring-billed, and California. The dark eye eliminates Ring-billed. The long straight bill eliminates Mew.

This third-year California Gull was photographed by Greg Gillson at Puerto Penasco (Rocky Point), Sonora, Mexico in May 2007. But note that California Gulls breed in Oregon and birds exactly as this one can appear anywhere in Oregon.

The bird on the adjacent rock might not have fooled as many. Note the wide tail band on this bird (Ring-billed has only a narrow tail band). Also note the all-dark bill tip.

* - The "Ring-billed Gull... NOT!" is first on Don Roberson's list of Ten Most Misidentified Birds in Monterey County.

Guesses:
Ring-billed Gull 9
California Gull 3
Thayer's Gull 2
Mew Gull 1

Correct responses, in order received:
Vjera Thompson, Eugene, OR
Mike Denny, College Place, WA
Linda Fink, Grand Ronde, OR