In general, February is the nadir of the year for a Vineyard birder, with numbers and diversity at their lowest. Mortality and migration have emptied many species entirely from our region, and the first hints of northbound spring migration often don’t appear until the very end of the month.
But for a gull enthusiast — and I plead guilty as charged — the shortest month may also be the best. While gulls of one kind or another can be found here year-round, the shortest month often brings unusual visitors. And even if only the usual gulls are present, the challenging conditions of winter often prompt interesting, even dramatic behavior on their part.
Three common species are always easy to find in winter, and indeed the trick to spotting an unusual gull is knowing these species inside-out. Most numerous are generally the herring gulls: large, gray-backed, pink-legged adults are what most non-birders mean when they use the imprecise name “sea gull.” Still larger, with a massive beak and a jet-black back when mature, is the great black-backed gull. Dainty compared with these two species, though still a good-sized bird, is the ring-billed gull, with yellow legs and, true to its name, a black band around the bill.
But part of the challenge of gull-watching stems from the fact that only some individuals sport adult plumage. Gulls take from two to four years to mature, and during those years, they pass through a sequence of plumages, usually starting with a dark, mottled juvenile plumage and gradually working toward the gray back and white underparts of an adult. Facility at gull ID means getting familiar with the full range of plumages, and the full range of individual variation within each age class. True expertise at gull ID is the product of decades of observation.
Happily, gulls are active, intelligent birds, with behavior that is rewarding to watch even if you can’t put a name to the species you’re seeing. True generalists, gulls of any kind are adept at finding anything edible, and creative in catching and eating it. From Dumpster diving to capturing smaller birds, gulls can do it all.
Their strategies for shellfish are a good example. Gulls, especially the larger species, are devoted predators of shellfish, and can be seen taking clams, scallops, whelks, and crabs. Typically, gulls find their prey in shallow water, often taking advantage of low tide to hunt. Sometimes they simply swim over likely areas, tipping up to grab prey when they spot it. In slightly deeper water, a swimming gull may flip into the air and make a shallow dive to snag a scallop; gulls may even dive, osprey-like, from patrolling flight, immersing themselves completely to reach their target.
To eat hard-shelled mollusks, gulls often fly aloft with their victim and drop it on a hard surface (Beach Road between Oak Bluffs and Edgartown and the Lagoon boat landing are two great place to watch this behavior). Crabs, in contrast, are simply flipped onto their backs and bashed open with a few hard whacks of the beak. Gulls lack the powerful, grasping claws of terrestrial birds of prey — but they manage fine with the equipment they have.
Also fascinating is a behavior called “kleptoparasitism”: stealing prey obtained by other species. If scoters or eiders are feeding actively, for example, there will usually be a few gulls in attendance as well. If a duck surfaces with a clam or mussel in its beak and can’t swallow it promptly, it is likely to find itself pecked and pestered by a gull until it has to drop its prey, which the gull promptly snatches and flies away with. Kleptoparasitism sometimes ends in the duck being battered to death or drowned — an indication of how powerful gulls are, and how intent on their purpose.
In addition, to our three large, common gulls, a variety of other species are possible in February. Some are surprisingly small: Bonaparte’s gull, for example, with flashy white patches on its outer wings, is about the size of a very lanky pigeon. And the aptly named little gull, a rare but fairly regular visitor here, is even smaller. Also possible here are glaucous and Iceland gulls, about the size of great black-backed gulls and herring gulls, respectively, but much paler in all plumages and lacking significant black in the wing tips.
In all, the well-prepared Vineyard birder needs to become familiar with about a dozen gull species that are regular in our region. And given the mobility of these birds, which can literally wander the world, one wants to stay alert for several more possibilities, including species from the West Coast or even from another hemisphere. So many species, each occurring in multiple plumages (and that’s not even counting hybrids, which occur quite regularly!): It’s no wonder that among serious birders, gull identification is currently considered the area of greatest challenge.