A New North American Larus? - The "Giant" Herring Gull

An unfortunate truth of the so-called "gulling community" is that many members of this group have failed to separate the gull-watcher and the bird-watcher. The pursuit of Larus is so utterly far removed from the pedestrian hobby of birding that to conflate the two is an insult to the very nature of this complex family. Alas, this is not the mindset of many self-proclaimed "gullers", who would rather stretch each and every specimen that does not fit neatly into the pre-defined norms of a "species" into its own distinct taxon. These hobbyists, more akin to common twitchers than true Larophiles, seek order where none exists. They impose their sterile taxonomic fetishes upon a lineage that thrives in the gray.

And so, few Larus remain unmolested by the eager scalpels of these misguided souls in their attempt to carve structure into a genus that sneers at rigidity. This mentality has given rise to a host of mass delusions, including but not limited to "Thayer's Gull", two species of Mew Gull ("Common" and "Short-billed" of Eurasia and North America, respectively), and a complex of large West Coast gulls with mantle and primary shades ranging clinally from pale to dark that has been split into no fewer than five species. Yet, a genuine source of "good" splits is entirely untapped: the humble North American Herring Gull. An abundant (or rather, successful) denizen of coasts, lakes, landfills, and northern forests, this supreme Larus is often spared the wrathful scrutiny of taxonomists. Perhaps as a result of its omnipresent and superficially accessible nature, hot-blooded "gull-watchers" take limited interest in it. Through decades of observations and research, I have found that at least three distinct breeding populations of Herring Gull occur on the North American continent: the Atlantic Herring Gull of the East Coast, the Eastern/Taiga Herring Gull of the Great Lakes and boreal forest, and the Northwestern Herring Gull of Canada's arctic islands (classified by most authorities as "Thayer's Gull"). However, my work on Herring Gulls has also revealed a strong species candidate within the complex. This article details my findings pertaining to the previously unacknowledged "giant" or Greenland Herring Gull, along with the substantial evidence suggesting that it is deserving of species consideration.

Whilst scanning flocks of Larus on the Great Lakes and Atlantic Coast, I have regularly encountered individuals that, despite otherwise fitting neatly into the Herring Gull designation, are roughly 30-40% larger than adjacent birds. Though it is easy to dismiss such birds as cases of individual variation, I have also noted minor yet consistent differences in the structure and plumage of these giant Herring Gulls. Most obviously, they possess ever-so-slightly heavier bills, blockier heads, and bulkier builds than their "typical" counterparts. When studied carefully, they also exhibit an infinitesimally lighter mantle shade. Given that these birds almost certainly hail from high latitudes, these may at first seem expected adaptions to northern climates, where larger body sizes serve as a thermoregulatory mechanism (see Bergmann's rule) and many species are paler overall. The differences do not end here, however. I have also noted a consistently abnormal primary pattern on these individuals. P10-P8 are distinctly two-toned, with noticeably pearly inner webs contrasting with dark outer webs. P7-P1 are exceedingly pale, with black restricted to broad subterminal bands on P7 and P6. First cycle birds may average slightly paler and more diffusely patterned than typical first cycle Herring Gulls.

Figure 1: a classic second cycle giant Herring Gull among typical adult Herring Gulls. Aside from the significant size discrepancy, this bird appears much bulkier and more square-headed. Photo by Akira Takemura, Ebird web site.

Figure 2: a standard giant Herring Gull primary pattern as described above. Photos by David Brown, Ebird web site.

Additionally, none of the birds I or others in my network have observed display intermediate characteristics. In short, this appears to be a discrete entity, with no evidence to suggest hybridization or clinal variation. This raises the question of where exactly this taxon originates. Most likely, it is a relatively rare form with nesting locales restricted to far northern latitudes. A likely candidate is the coastal cliffs of southwestern Greenland, where an isolated populations of Herring Gulls has been documented to breed. Nesting could also occur on northeastern Baffin Island or Devon Island in the Canadian arctic.

More to come,

Gene.