Bird of the Month - January 2003
 

Glaucous Gull
Larus hyperboreus

by David Fix

At some point in the mind of a birder, there comes the general leap of conception that gulls aren’t merely esthetic objects—with practice, many can be distinguished, species from species.  Causing this shift in awareness to follow a bit of a rocky course is the apprehension nearly everyone feels at attempting to ID large gulls.  Indeed, years are required to become proficient.  And there are no ‘experts’ who place a name on each gull they look at!  With hybridization among related taxa further muddying the picture, the complexities facing the gull-watcher can seem a howling wilderness of potential wrong choices.  For these reasons, an encounter with a species or plumage that is fairly distinctive offers an encouraging moment of orientation.  Sooner or later, one’s first Glaucous Gull (Larus hyperboreus) appears.  Large, and with strikingly pale wing-tips, Glaucous Gulls often stand out among a crowd of smaller, darker-winged gulls. 

Glaucous Gulls are northern-nesting birds—the species name “hyperboreus” means ‘beyond the north wind’—which have a circumpolar breeding range.  They are powerful predators as well as scavengers, eating small rodents, birds, and birds’ eggs during the brief Arctic summer.  In winter, a very small proportion of the population drifts southward to shores and waters of the temperate eastern North Pacific Ocean.  From late fall into early spring, a few of these gulls occur along the California coast.  Here in the Redwood Region, one (almost always), two (rarely), or three (exceptionally!) may be found associating with big flocks of large gulls gathered at feeding or loafing sites.  As a tiny number usually winter south of us, the occasional south- or northbound migrant is sometimes detected in apparent daytime passage from coastal vantage points, flying through the surf zone alone or in the loose company of other gulls.

Since (a) individuals representing the younger age classes move farthest south, and (b) the mortality curve dictates that first-year immatures will typically make up a disproportionately large fraction of the total population, most of the Glaucous Gulls seen here are in their first year of life.  So how will you know a first-winter bird?  Four key marks are (1) generally conspicuous paleness, the whole bird being either palest latte color or whitish and finely ‘freckled’ across the back and wings;  (2) a heavy bright pink bill with a sharply-demarcated black outer quarter of the bill;  (3) wingtips which are white, or nearly white, and are nearly unmarked, and (4) large size-- first-winter birds are usually the size of a Glaucous-winged Gull or just slightly larger.  A few are by some margin the biggest gull in the flock, others might ‘tie’ for size, while still others may be only the bulk of a Western Gull.  Second- and third-winter birds are seldom seen here.  Adults are rare;  they are known by their immaculate white wing-tips, very pale gray ‘mantles’, and yellow eyes.

It’s best to learn gulls in the company of an experienced observer.  Such a person may point out subtle but regular identification pitfalls involving look-alikes such as Glaucous-winged Gulls in worn late spring plumage, other gulls with pink-based bills, and the possibility of hybrids (for example, Glaucous X Glaucous-winged and Glaucous X Herring are known to be produced in Alaska and are suspected to show up on the northern California coast).  But armed with several field guides and a willingness to ‘let them go’ sometimes, any birder can have fun taking a look for one of these northern visitors and, with patience, luck, and a good long study, enjoy a Glaucous Gull.