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[Mea culpa! For whatever reason or combination of reasons, I made a huge boo-boo in the November 2011 photo quiz. The primary reason for this mistake is that I had intended to use a particular picture that illustrated a point that I wanted to make – one different from the point that the picture that I actually used makes. Thus, I came to write the solution to that quiz with the wrong species in mind. Then, I made a classic birder mistake and assumed that I was right and explained why I was right, overlooking all of the obvious reasons that my original solution was wrong. Way wrong. Can I get a do-over?]
Ugh, another gull! And, one of which we cannot see the bill. Ugh! However, we’ve got a great look at the bird’s wingtip pattern, which should go a long way toward identifying the bird.
Ageing gulls of uncertain ID is always a good first step. Our quiz bird seems fairly clean gray and white – with black wingtips, of course – and with no black in the tail, features that tell us that it is probably an adult. However, the bird does sport dark shaft streaks on the coverts associated with the outermost primaries on both wings, a sign of immaturity. This fact, in combination with a feature noted later in this essay and the aforementioned lack of black in the tail, may mean that the bird has not quite reached definitive (= adult) plumage. Despite that slight immaturity, enough of the features of the wingtip are adult enough to be used as if the bird were a full adult. Before getting to wingtip pattern – the reason for using this picture, we can eliminate the dark-mantled gulls straight away, leaving us with the paler-mantled/black-wingtipped species: Mew, Ring-billed, California, Herring, Thayer’s, and Yellow-legged.
When studying wingtip pattern, it is incumbent upon us to know what, exactly, to look at and the nomenclature of those features. Critical features here are mirrors and tongues, both of which are characters of outer primaries, and primary tips. Mirrors are white patches near the tip of the 10th, or outermost, primary (p10) and, in some species, p9. Mirrors are always abutted by black or blackish on those species with black wingtips. Tongues are patches of white on the inner webs of, variably, p5-p8. Tongues are always abutted distally by black or blackish (in those species with black or blackish wingtips) and proximally by the adult upperparts coloration (some variation of gray to blackish). The very tips of individual primaries are tipped white in most gull species, with the pattern of which primaries being tipped helpful in identification.
With the above firmly in mind, let us look at the right wingtip. There is a large mirror on p10 that nearly reaches the feather tip, while p9 lacks a mirror. The tongues on p5-p8 are quite thin and small, being less than obvious. The bird’s left wing, however, is a bit different, with a small, but well-defined, mirror on p9. These differing wingtip patterns suggest at least some of the variation in this character inherent in the species.
Just on the strength of the size of the mirrors, we can tentatively eliminate from consideration Mew and Thayer’s gulls, as those species show more-extensive mirrors on p9. The extent of the black in the wingtip can help us rule out other species. California and Yellow-legged gulls have more extensive black, with that color extending distally on both webs on p8 to nearly the base of that feather, which eliminates any possible p8 tongue; our bird’s most obvious tongue is on p8. Even though our bird has indistinct tongues, those tongues are still much more striking than any sported by Ring-billed Gulls, which lack a p8 tongue, as the black on that feather extends about halfway to the primary covert. Additionally, Ring-billed Gull lacks white tips to the outer two primaries, unlike on our quiz bird. I took this picture of an adult Herring Gull in North Cape May, Cape May Co., NJ, on 18 February 2011.
An interesting feature of this Herring Gull lies in the p9 mirrors, even above the fact that our quiz bird has p9s of differing patterns. Eastern Herring Gulls tend to medium-sized mirrors on p9, while western Herring Gulls typically lack p9 mirrors. Something that birders can help us solve, is where that line between eastern and western smithsonianus Herring Gulls lies. Simply make note of the number of mirrors per wing of fully adult Herring Gulls. I am at a loss, however, to suggest a place to publish that information.
The following people (listed by submission date beginning with the earliest) submitted correct answers for the November Bird Photo Quiz—Herring Gull:
The following list shows the number of submissions for each species guessed.
The photo and answer for this quiz were supplied by Tony Leukering.