Monday, November 9, 2009

Thayer's Gull- A species with no future

Few birds have garnered as much taxonomic debate as Thayer's Gull. Considered a subspecies of the Herring Gull by the AOU until 1973 it earned full species status based largely on the research of A.H. Macpherson and Neil Smith in the 1960's. Neil Smith's work which suggested Thayer's and Kumlien's Gulls mated assortatively on Baffin Island is now viewed with much scepticism. Repeated studies by Canadian ornithologist subsequently have strongly supported nonassortative breeding between these two taxon. Many experts including the BOU consider Thayer's and Kumlien's as subspecies of the Iceland Gull. Ron Pittaway a respected authority on this subject has published an excellent account of the history of this taxonomical debate which can be accessed at

Adult Thayer's Gull

It seems inevitable that the AOU will eventually lump Thayer's with Iceland and Kumlien's but until then I will cherish it species status despite the overwhelming evidence to the contrary.

Thayer's Gull first came to the attention of birders in the 1960s and was first illustrated in Godfrey's classic Bird's of Canada published in 1966. Gosselin and David were the first to publish photographs and a detailed description in 1975 in American Birds. Subsequently in a tour de force publication in Birding Paul Lehman described and provide illustrations and photographs of all age classes of Thayer's Gull. Specimens of Thayer's Gull were collected on the lower Great Lakes as early as the late 60's. Ron Pittiway may have been the first "birder" to identify a Thayer's Gull in the Great Lakes region identifying a first winter Thayer's Gull in Hull, Quebec (first provincial record)on November 11, 1973. The bird was later collected and the identification confirmed by Earl Godfrey.

Juvenile Thayer's Gull

I vividly remember identifying a first winter Thayer's Gull with my father at the Orillia Landfill on Nov. 28th, 1975. We used Godfrey as a reference to differentiate this bird from Kumlien's and Herring Gull. I subsequently saw adult birds on the Niagara River probably the most well know location to view this species in the east.

In the Sault Area at the junction of Lakes Huron and Superior Thayer's Gull is a regular fall visitor. Juvenile birds which predominate usually arrive in late October with birds persisting into early January most years. In season one or two Thayer's Gulls are usually seen on most visits to local landfill. Traditionally Kumlien's Gulls have outnumbered Thayer's by at least two to one. The last few seasons has seen increased Thayer's with as many as five at a time. This fall Thayer's definitely seem to outnumber Kumlien's. In the western parts of Lake Superior Thayer's are the predominant taxon with Kumlien's being uncommon.

Second winter Thayer's Gull

The consistent presence of both Thayer's and  Kumlien's Gulls makes this an excellent location to study the  cline between these taxon, especially in first year birds. Observation opportunities at very close range and for prolonged periods allow for careful study and superb photographic opportunities.  Many bird are seen that are not comfortably classifiable into either taxa. Theses 'intergrades" are commonly seen and probably make up close to 20% of the combined total. Most of these birds look like petite "pale" Thayer's but a distinct  ''silver'' form is occasionally seen which is somewhat mystifying to me and will be discussed in a subsequent post.

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