124 Questions about Thayer's Gull Richard C. Banks and M. Ralph Browning

Two recent papers (Howell 1999, The Committee on Classification Pittaway 1999) have expressed and Nomenclature is a conservative opinions about the taxonomy of group that is inclined to maintain Thayer's Gull (Larus thayeri) and the taxonomic status quo until its presumed close relatives. Both there is sufficient published scien­ express the viewpoints of the tific evidence for us to consider and authors, seemingly based on reports vote on a change. Aside from the of unpublished studies weighted by publication of opinions, there has opinions published by others. Both been nothing to instigate even seri­ chide the AOU Check-list ous discussion of Thayer's Gull by (American Ornithologists' Union the committee, although the com­ 1983, 1998) for retaining specific mittee is aware that there is a prob­ status for Thayer's Gull, and lem and that its treatment may be Pittaway (1999) suggests that "The wrong. There are, in fact, a fair AOU is bound to change its posi­ number of species in that category. tion as more authors independently The committee may eventually adopt a taxonomy recognizing that change its position, but the reason Thayer's is a form of the Iceland will not be unfounded opinions of Gull". others. This response is at two levels. Some years ago, we (B and B) One of us (RCB) chairs the AOU's compiled a taxonomic history of Committee on Classification and Thayer's Gull similar to that of Nomenclature (=Check-list Com­ Pittaway (1999). Rather than lead­ mittee) and will respond to what ing us to conclusions, our compila­ "the AOU is bound to..." do. tion generated additional questions Beyond that, we have long had an that we believe must be addressed intense interest in the systematic before an informed taxonomic deci­ position and taxonomy of the sion can be made. Our studies since Thayer's Gull complex and have we posed these questions in 1990 done a great deal of research on it have addressed some of these prob­ which, unfortunately, we are not yet lems, but to our knowledge none of prepared to publish. The length of them has been fully resolved. Along that interest is suggested by the fact with our questions, we give some that most of the comments below comments on why they remain are from a paper that we presented unanswered. What follows is only to a meeting of the Wilson slightly modified from our oral pre­ Ornithological Society in 1990. sentation.

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As everyone knows, Thayer's characters of Thayer's Gull in the Gull was named as a species in east were stable, showing little or 1915, reduced to the level of a sub­ no intergradation with the Herring species of the Herring Gull, Larus Gull, but that in the western Arctic argentatus, a few years later, revived there was complete and perfect as a distinct species in the 1970s, intergradation of characters so that and is now considered by some to "it is difficult to tell where one form be a subspecies of the Iceland Gull, begins and the other leaves off". L. glaucoides. The nomenclature Manning et al. (1956) similarly and history of Thayer's Gull is so found no sign of intergradation closely tied to that of Kumlien's with the Herring Gull in the Frozen Gull, first described as a species, L. Straits area of eastern Canada, even kumlieni, in 1883, and now general­ though the range of variation there ly considered a subspecies of the was sufficient to overlap Kumlien's Iceland Gull, that it is impossible to Gull, but contra Taverner, they had discuss one without frequent refer­ no difficulty in assigning western ence to the other. birds. One is forced to wonder if Manning et al. had a better set of 1. Is the Thayer's Gull the same criteria than Taverner. At any rate, bird in the western part of its range their confidence was so much better as in the eastern part? The original that they did not give their criteria description of Thayer's Gull was or the distinguishing characters of based on birds breeding on the two forms. Ellesmere Island, although two Is it possible that the western birds from the Arctic coast of birds assigned to thayeri are differ­ Alaska were also assigned to the ent from the eastern birds? We can­ species. No information on the true not tell, because eastern and west­ range of the species was then avail­ ern thayeri have never been directly able. Dwight (1917) quickly placed compared in the literature. Most it in the Canadian Arctic Arch­ published measurements of thayeri ipelago' and extended its range as lump all specimens available into a far west as Banks Island by assign­ single sample, and aside from the ing to the form several specimens very large numbers of Thayer's from intervening localities. The Gulls measured by Smith (1966) on August adult from Alaska has been Baffin Island and in the Frozen ignored in subsequent statements Straits area, all told there are mea­ of the breeding range, but who surements in the literature of fewer knows if that bird was a breeder, or than 50 male Thayer's Gulls - and if it was even what we now call some of these may be the same Thayer's Gull. birds measured by different work­ Taverner (1933) stated that the ers. Despite the fact that Thayer's

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Gull acts like a species in the east, ature said it occurred abundantly, relative to the Herring Gull, and but to some extent all over North like a subspecies in the west, America. It is not only observations according to some accounts, no one or sight records that we wonder has reported looking at the possibil­ about; we wonder also about identi­ ity of differences in eastern and fications of specimens. western birds. Consider the following. In 1945, a gull taken in the Niagara Falls 2. With that in mind, we ask how area was sent to the American reliable are identifications of Museum where it was identified as Thayer's Gull? One of our favourite L. glaucoides kumlieni. Another quotations is from a 1986 American "almost identical" bird taken in the Birds Regional Summary, where same area in 1957 was therefore Ken Able noted that "A bird match­ also considered to be Kumlien's, or ing the description of what usually Iceland, Gull. After Thayer's Gull passes for an adult Thayer's Gull was recognized as a species, those was seen ...." specimens were considered to be As a subspecies, Thayer's Gull the first records of Larus thayeri for was reduced to observational obscu­ the Niagara Frontier region rity only two years after it was (Andrle 1969). There is no indica­ described. There were few birders tion that the specimens were re­ then, so there is no record of a lot of examined or re-compared - just re­ these gulls being seen. Field workers identified. We wonder which in the Canadian Arctic did identify species they really represent, and and study Thayer's Gulls, and muse­ why, if the first was Thayer's Gull um workers labeled some speci­ after 1973, it was not identified as mens with that name. But many of L. argentatus thayeri originally. us grew up before there was an enti­ Kumlien's Gulls did not automati­ ty called Thayer's Gull to be seen on cally become Thayer's Gulls when field trips, and not surprisingly there thayeri was split from argentatus. are few records of it in most of the We wonder, too, about records for literature for about 50 years, and no the north shore of the Gulf of St. illustrations of it in field guides of Lawrence, where what appears to those times. Soon after studies pur­ be the same individual has been ported to show that it didn't inter­ identified in the literature as breed with anything and it was ele­ Thayer's, Herring, and Kumlien's vated back to species status, gull. Most current literature seems Thayer's Gulls popped out of the to reflect the first identification, by woodwork everywhere, showing up Dwight (1925), and ignore the two on life lists, state lists, and so on, par­ later identifications. How can the ticularly in the west where the liter- range of a form be recorded if we

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don't know which identification of extending only to Pond Inlet, which an individual is correct? is very far north, and Kumlien's Taverner (1933) wrote in refer­ Gull was found north only to ence to Kumlien's Gull: "Juveniles Cumberland Sound, which is pretty of sure identity have never been far south. Wynne-Edwards (1952) positively demonstrated and speci­ noted that there were no gulls of mens so designated have been the glaucoides-argentatus group in named more by process of elimina­ several intermediate localities, and tion and careful judgement (neither that there was a gap of about 500 of which I care to question here but miles (800 km) on the east coast of suggest possibilities of doubt) than Baffin Island without any gulls of by evidence of parentage". Surely this group. Maps published by that statement could be extended to Macpherson (1961) show this large Thayer's Gull, many records of gap. There were, however, several which are based on juvenile birds. colonies of Glaucous Gull (Larus hyperboreus) known from the area, 3. Have there been recent so it is not strictly a matter of the range extensions of either or both area being unexplored. Yet, for Thayer's and Kumlien's Gulls creat­ some reason, Smith went to Home ing a zone of secondary contact Bay, in the middle of this no-gull's­ where they are now reported to land, in 1961 and found not only interbreed? On Southampton Glaucous but also Thayer's, Island, Sutton (1932) found only L. Kumlien's, and Herring Gulls, argentatus on the south side of the breeding in variously mixed island. Manning et al. (1956) found colonies in large numbers, and mat­ L. thayeri in a small area at the ing assortatively. In 1975 and 1976, northern tip, and Smith (1966) Knudsen revisited Home Bay and found Thayer's much farther east­ found Thayer's and Kumlien's ward. Kumlien's were unknown interbreeding (Godfrey 1986, Snell from the island. But Gaston and 1989). Decker (1985) found Thayer's and Thus, by early accounts, Kumlien's interbreeding on the Thayer's and Kumlien's gulls were north side of the Bell Peninsula, the well separated geographically, but easternmost part of Southampton suddenly they were interbreeding Island, where neither species had all over the place, especially where been reported - although perhaps neither had been before. If these no one ever had a chance to look are truly zones of secondary con­ there. tact, how much do they tell us about On Baffin Island, Soper (1928, species relationships? Might not the 1946) reported that Thayer's Gull situation stabilize in a decade or was confined to a northern area two, as it may have in a similar situ-

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ation in orioles in the Great Plains? birds to form an unbroken continu­ How much do we need to know um from dark to white, and before we rush to judgement? Knudsen's criteria are not available, these data are not readily inter­ 4. And anyway, what happens pretable. when thayeri and kumlieni inter­ The results of any of these inter­ breed? Normally, when two species breedings, in terms of young pro­ interbreed, the progeny are interme­ duced, have never been reported, so diate in most respects. If this hap­ we do not know·(except as judged pens frequently, and there is a fair from the range of variation) whether number of F-1 hybrids, they may the forms are interfertile. No young interbreed and backcross and form a from mixed nests have ever been hybrid swarm. Perhaps this is the sit­ collected or raised to adulthood, so uation in the Thayer's-Kumlien's we don't know what they look like. Gull, where individual variation was And when you get right down to it, said to be so extensive as to bridge seeing two birds at a nest does not the difference between the two necessarily mean that those two types even before they were known birds copulated and laid the eggs in to interbreed. Yet where they occur that nest, if there are any. Most of together, investigators seem to have these nests have been viewed only no trouble telling them apart. Smith from afar, e.g., from a boat. apparently had no trouble on Baffin Island where they bred assortatively. 5. Even if interbreeding is regu­ Gaston and Decker (1985) had no lar and mixing is thorough, why is trouble on Southampton Island, Kumlien's Gull, and therefore reporting six pairs of Thayer x Thayer's, associated with the Iceland Thayer, five pairs of Thayer x Gull? When it was first described, Kumlien, and one pair of Kumlien x kumlieni was differentiated from Kumlien. They did mention two and compared to the Glaucous­ intermediate birds, but did not list winged Gull, Larus glaucescens, of them among known pairs. How do the Pacific coast. The English name you tell intermediates when the proposed was "Lesser Glaucous­ range of variation bridges the gap? winged Gull." Its similarity to the Snell (1989) wisely didn't use Iceland Gull was noted and a possi­ names, but reported dark- and light­ bIe relationship mentioned, mainly winged pair combinations and cited on the basis of color. Knudsen's unpublished paper as Taverner (1933) stated that reporting pairs consisting of light x kumlieni "is of the Herring Gull dark, two of "fairly intermediate" type" with the "wing tip pattern coloration, and intermediate x light­ washed out to grey and greatly winged. Since Snell considered the reduced in area. In all other charac-

ONTARIO BIRDS DECEMBER 1999 129 ters it seems indistinguishable from really provide any definitive evi­ that species." Manning et al. dence of relationship. Noone has (1956:98fn) quotedWynne-Edwards reported a contact zone between as writing that "in life Kumlien's Iceland Gulls and Kumlien's Gulls. Gull does not differ greatly from the Indeed, they are well separated by Herring Gull except in the paler the Davis Straits. pigmentation of the primaries, Is it conceivable that Thayer's whereas they were 'obviously differ­ and Kumlien's could represent a ent from Iceland Gulls on any but species distinct from both Herring the most superficial examination"'. and Iceland? That seems to be Rand (1942) was the first to list about the only combination that has kumlieni as a subspecies of the not been proposed seriously. Iceland Gull, on the basis of a series of immatures intergrading in color. 6. And finally, has everyone for­ Salomonsen (1950) thought that gotten that regardless of one's con­ both kumlieni and thayeri should be cepts of the characters of these treated as the same species as the birds, or how many ofeach are iden­ Iceland. Characters he gave were tified in the field in or out of the smaller size, less melanin on the pri­ expected range, their nomenclatural maries, and "having a very differ­ disposition depends on the charac­ ent, much paler juvenile plumage". ters of the type specimens? Despite But according to Godfrey (1986), all that has been written about some young thayeri are darker than Thayer's Gull in the past two or Herring Gulls. three decades, there is no indication The fact that both Thayer's and in the literature that anyone Kumlien's Gulls have dark fleshy (besides us) has examined the type eye rings, in contrast to the yellow specimen or the rest of the type eye ring of the Herring Gull, has series since Dwight in the early been of primary importance in 1920s. The same can be said for merging these two forms. This eye Kumlien's Gull. Even Howell ring is also dark in the Iceland Gull, (1999), who gave measurements of and the Glaucous-winged. Both birds from the Museum of Kumlien's and Thayer's have vari­ Comparative Zoology, does not able dark flecking in the iris, in con­ mention examining the type of thay­ trast to the pure yellow iris of the eri, which is housed there. Herring Gull and the yellow iris of The purpose of this paper is not the Iceland Gull. There is much vari­ specifically to rebut or refute any­ ation reported in iris color of both thing published on the subject by Thayer's and Kumlien's gulls, rang­ others. Rather, we hope that it might ing from nearly pure yellow to very stimulate work that will eventually dark. Eye color and contrast do not lead to the resolution ofthe problem.

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Literature Cited American Ornithologists' Union. 1983. Pittaway, R. 1999. Taxonomic history of Check-list of North American birds. 6th Thayer's Gull. Ontario Birds 17: 2-13. edition. American Ornithologists' Union, Rand, A.L. 1942. Larus kumlieni and its Washington, D.C. allies. Canadian Field-Naturalist 56: 123­ American Ornithologists' Union. 1998. 126. Check-list of North American birds. 7th Salomonsen, F. 1950. Gronlands fugle. The edition. American Ornithologists' Union, Birds of Greenland. Ejnar Munksgaard, Washington, D.C. Copenhagen. Andrle, R.F. 1969. "Thayer's" Gull in the Smith, N.G. 1966. Evolution of some arctic Niagara Frontier Region. Auk 86: 106-109. gulls (Larus): an experimental study of Dwight, J. 1917. The status of "Larus thayeri, isolating mechanisms. Ornithological Thayer's Gull". Auk 34: 413-414 Monographs 4. American Ornithologists' Dwight, J. 1925. The gulls (Laridae) of the Union, Washington, D.C. world: their plumages, moults, variations, Snell, R.R. 1989. Status of Larus gulls at relationships and distribution. Bulletin of Home Bay, Baffin Island. Colonial the American Museum of Natural History Waterbirds 12: 12-23. 52: 63-401. Soper, J.D. 1928. A faunal investigation of Gaston, A. J. and R. Decker. 1985. southern Baffin Island. Bulletin 53. Interbreeding of Thayer's GUll, Larus National Museum of Canada, Ottawa. thayeri, and Kumlien's Gull, Larus glau­ Soper, J.D. 1946. Ornithological results of coides kumlieni, on Southampton Island, the Baffin Island expeditions of 1928-1929 Northwest Territories. Canadian Field­ and 1930-1931, together with more recent Naturalist 99: 257-259. records. Auk 63: 223-239. Godfrey, W. E. 1986. The Birds of Canada. Sutton, G.M. 1932. The birds of Revised edition. National Museums of Southampton Island. Memoirs of the Canada, Ottawa. Carnegie Museum 12(2), section 2. Howell, S.N.G. 1999. Shades of gray: the Carnegie Museum, Pittsburgh. catch 22 of Thayer's Gull. Birders Journal Taverner, P.A. 1933. A study of Kumlien's 7: 305-309. Gull (Larus kumlieni Brewster). Macpherson, A.H. 1961. Observations on Canadian Field-Naturalist 47: 88-90. Canadian Arctic Larus gulls, and on the Wynne-Edwards, V.C. 1952. Zoology of the taxonomy of L. thayeri Brooks. Arctic Baird Expedition (1950) I. The birds Institute of North America Technical observed in central and south-east Baffin Paper 7: 1-40. Island. Auk 69: 353-391. Manning, T.H., E.O. Hohn and A.H. Macpherson. 1956. The birds of Banks Island. Bulletin 143. National Museum of Canada, Ottawa.

Richard C. Banks, USGS Patuxent Wildlife Research Center, National Museum of Natural History MRC-111, Washington, DC 20560-0111, U.S.A.

M. Ralph Browning, 15373 Elk Creek Road., Trail, OR 97541, U.S.A.

ONTARIO BIRDS DECEMBER 1999