02 July 2017

The Post-Thayer's Era

And so Thayer's Gull has at long last been put to rest. The AOS (AOU) Committee on Classification and Nomenclature has voted unanimously on the proposal to lump thayeri with Iceland Gull (2017-C-7) .

The question was not so much whether there was an irrevocable need to retire the species altogether. Rather, the matter of contention was that there was never sufficient evidence to recognize the Iceland Gulls (nominate glaucoides, kumlieni and thayeri) as unique "biological" forms. I could not agree more. Whether we call all 3 taxa Iceland Gulls or any other suitable English name is inconsequential - so long as they're regarded as conspecifics in the present.

First cycle Thayer's [Iceland] Gull (L.g. thayeri). Waukegan, Illinois. December.

The overwhelming majority of birders alive today, including myself, have always known Thayer's Gull as a species. Witnessing a taxonomic lump of this magnitude is, without doubt, sobering.

Yet, how many of us were never aware that the decision to give Thayer's species status in 1973 was based largely on false pretenses? How many of us don't realize that thayeri has never been systematically described throughout its breeding range? How many birders still don't know of the multiple accounts that describe pale-winged and dark-winged birds purportedly interbreeding in several regions across arctic Canada? Add to this the fact that virtually zero amount of genetic work has been done in order to better understand these 3 similarly-behaving taxa, and it becomes clear that this lump was imminent!

An intermediate thayeri-kumlieni type that I prefer not to stubbornly label.
Michigan City, Indiana. January.

An intermediate adult thayeri-kumlieni type. Whiting, Indiana. February.

How is it, then, that anyone would be satisfied with checking off a "species" cloaked with so much ambiguity!? But I digress. This post isn't to argue the merits of lumping thayeri with the Iceland Gulls - that battle has already been fought and won (you can read my detailed opinion on this subject in a post I wrote earlier this year, Thayer's the Iceland Gull - One Species. Also, see my commentary on the recent proposal in Birding, June 2017. V49 N3).

First cycle Kumlien's [Iceland] Gull (L.g. kumlieni). Whiting, Indiana. December.

Adult Kumlien's [Iceland] Gull (L.g. kumlieni). Hammond, Indiana. February.


Moving Forward

I'd like to suggest that this classification will give fresh impetus to gull-watching and gull study in North America. Gone are the days where circular reasoning is permitted when discussing these forms. Intermediate and perplexing individuals will be called just that, with no impulse to pretend we understand their absolute pedigree. Rightfully, a hefty burden of proof is placed on any contemporary worker who attempts to untangle this complex.

Iceland Gull (L.g. glaucoides). First Cycle. Volusia County, Florida. January.

It's my hope that we'll build on the current identification papers at our disposal, and maybe, just maybe, a few brilliant students of ornithology will eventually get up to the breeding grounds and carefully study these high arctic denizens. At the very least, perhaps increased banding efforts, the use of GPS tracking and the collection of blood samples will be carried out throughout the wintering grounds, for starters.

All is not Lost

The omission of Thayer's Gull from our "checklists" doesn't any more or less change reality. Over the last couple of days, I've read remarks on social media such as, "Great, now I can stop looking for them", as if the task of finding a Thayer's Gull is similar to finding a mythical dragon. 'Tis not.

Adult-type Thayer's [Iceland] Gull. Lake County, Illinois. February.

There will still be a sizable population of dark-winged birds that we will systematically identify as Thayer's [Iceland] Gulls come this Fall/Winter. The only difference is, now, we can enjoy the inherent variation found in this complex without illogical consequences.