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Articles

Taxonomic History of Thayer's Gull

Ron Pittaway

In this article, I present a chrono­logical review and historical per­spective on the taxonomy ofThayer's Gull (Larus thayeri). It ishoped that this overview will be ahelpful contribution to the ongoingdiscussion of this confusing gull. Ilayout the historical and currentviews on Thayer's Gull taxonomyso that you can make your owndecision. In the end, I give you myopinion on Thayer's Gull.

In reading the following chron­ology, it is important to keep threepoints in mind: (A) Thayer's Gullwas generally treated as a sub­species of the Herring Gull (L.argentatus thayeri) from 1917 until1973 when the AOU (1973) gave itfull species ranking; (B) Kumlien'sIceland Gull (L. glaucoides kum­lieni) has always been the problemtaxon because it is highly variableand it exhibits intermediate charac­ter traits between Thayer's andnominate Iceland Gulls; and (C) thelimits of variation in both Kum­lien's and Thayer's phenotypeshave not been adequately definedby most of the following authors.

1. W.S. Brooks (1915) described anew species of gull, naming itThayer's Gull (L. thayeri), based on

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a very few specimens collected in1901. The designated type specimenis from Ellesmere Island. He com­pared it to Kumlien's Gull (L. kum­lieni), then considered a full species,and to Herring Gull (L. argentatus).

2. Dwight (1917) next consideredThayer's Gull to be a subspecies ofthe Herring Gull (L. smithsonianusthayeri), based on about 25 speci­mens, and supposed intergradationbetween thayeri and smithsonianus.

3. Dwight (1925), in his classic studyof gulls, again treated Thayer's as asubspecies of the Herring Gull. Heregarded Kumlien's Gull as ahybrid between Thayer's andIceland Gulls. Interestingly, Dwightnoted intergradation betweenThayer's and Kumlien's Gulls, butstill listed Thayer's as a race of theHerring Gull!

4. The AOU Check-list (1931) listedThayer's as a subspecies of theHerring Gull. It placed Kumlien'sGull on the hypothetical list as aprobable hybrid between Thayer'sGull and Iceland Gull.

5. Taverner (1933) regarded Kum­lien's Gull as a separate species. He

challenged Dwight (1925) and theAOD (1931), who consideredKumlien's to be a hybrid betweenThayer's and Iceland Gulls. Even ifthe Kumlien's population were ofhybrid origin, Taverner believedthat it should be treated as a sepa­rate species because it bred in purecolonies and not in association witheither Thayer's or Iceland Gulls.

6. Taverner (1937), in his Birds ofCanada, treated Thayer's as a sub­species of the Herring Gull. Hetreated Kumlien's Gull (L. kum­lien i) as a full species. Tavernernoted "much variation in the pat­tern [of the wingtips]. It may beunusually deep and extensive so toalmost suggest the thayeri form ofthe Herring Gull".

7. A. Brooks (1937) believed thatThayer's Gull would prove to be adistinct species from Herring Gull.He was the first to challengeDwight's (1925) treatment of thay­eri as a race of the Herring Gull.

8. Peterson (1947) was the guidethat I started with in the 1950s. Ithad a subspecies section in the backof the book that is still worth read­ing today. He said that someThayer's come so close toKumlien's that "it is a questionexactly what they are".

9. Salomonsen (1950/51) reported asmall population of Thayer's Gullsbreeding in the Middle ThuleDistrict of northwest Greenland.

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His description of Thayer's speci­mens from Greenland is similar toCanadian birds. Salomonsen statedthat Thayer's Gull was the highArctic form of the Iceland Gull. Hementioned two specimens ofKumlien's Gull from Greenland.Salomonsen said that the most nat­ural explanation for kumlieni was ahybrid population between glau­coides and thayeri.

10. Manning et al. (1956) in ananalysis of Thayer's Gulls on BanksIsland, Northwest Territories stated:"There is no difficulty in decidingthat the five adult specimens fromBanks Island are typical of the thay­eri population. A more complexquestion is the relationship of thispopulation as a whole to L.a. smith­sonianus on one hand and L.g.kumlieni on the other."

11. The AOD Check-list (1957) con­tinued to list Thayer's Gull as a sub­species of the Herring Gull. Therewas very little interest in Thayer'samong birders because it wasthought to be only a race of theHerring Gull and virtually nobodyknew how to identify it.

12. Parmelee and MacDonald(1960) treated Thayer's Gull as aseparate species. They included aphotograph of two adult Thayer'sfrom Ellesmere Island. One is a typ­ical Thayer's. In the second bird, theamount of dark in the foldedwingtips is well within the range ofmany Kumlien's Gulls. The field

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party from the National Museum ofCanada collected specimens ofThayer's Gull near Eureka onEllesmere (80 degrees north lati­tude). Parmelee and MacDonalddescribed the wingtip patterns ofthe specimens: "The tips of the pri­maries (excluding white mirrors)grade from dark grey to grey tovery light grey in the four males;from very dark grey (nearly black)to grey in four females. The fifthfemale has the entire wing tipswhite or nearly white and is theonly one of the series (both sexes)that differs greatly in wing tip pat­tern from the type specimen (seeDwight, 1917:413-4). According toA.H. Macpherson (verbal comm.),Thayer's Gulls with grey to lightwing tips appear to be numerous inthe breeding range only at high lat­itudes. The Eureka specimens bearthis out." The reason these palewinged birds from Ellesmere areclassified as Thayer's and notKumlien's is that they were collect­ed well within the breeding range ofThayer's and they are part of aninterbreeding population ofThayer's Gulls. However, these palewinged Thayer's suggest past intro­gression with Kumlien's, nominateIceland Gull or even GlaucousGull. Alternatively, they may justrepresent part of the variabilityfound in this population. A palewinged Thayer's originating fromEllesmere Island would be impossi­ble to tell from Kumlien's in thefield on the winter range.

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13. Macpherson's (1961) study ofArctic gulls was the most importantand pivotal work of its time. The bighurdle then was to prove thatThayer's was not a race of theHerring Gull. Macpherson foundthat thayeri and smithsonianusHerring Gulls were breeding sym­patrically (breeding ranges overlapwithout interbreeding). This is thebest test of a biological species.Macpherson also recommendedtreating Thayer's Gull as a sub­species of the Iceland Gull. He saidthe characters shared by kumlieniand thayeri "include preference forcliff-nesting, gregarious breedinghabits, and possession of a purplish­red orbital ring".

14. Godfrey (1966) was the first totreat Thayer's Gull as a separatespecies, based on Macpherson(1961) who reported Thayer'sbreeding sympatrically withHerring Gull and because NealSmith's personal communicationsto Godfrey reported that thayeriand kumlieni bred sympatrically onBaffin Island. Godfrey also hadaccess to Smith's PhD thesis.Godfrey's (1966) description andJohn Crosby's illustrations of adultThayer's in the first edition of TheBirds of Canada provided birderswith the field marks of adultThayer's for the first time.

15. Smith (1966) reported that hisresearch done at Home Bay, BaffinIsland, found kumlieni and thayerito be reproductively isolated, thus

behaving as separate species. It isnoteworthy that no subsequentresearchers have reached this sameconclusion. Smith reported that heconducted a number of ingeniousexperimental techniques; for exam­ple, he stated that he painted andchanged orbital ring colour thatinduced hybridization by establish­ing 55 Thayer's x Glaucous pairbonds! I recommend that you visit auniversity or museum library toread this now infamous study whichled the AOD (1973) to regardThayer's Gull as a distinct species.

16. Smith's (1967) study was fea­tured on the cover and in a majorarticle of the October 1967 issue ofScientific American. A good libraryshould have this issue or access to it.

17. Parmelee et al. (1967) reportedon ornithological investigations ofVictoria Island in the NorthwestTerritories. They listed Thayer's Gullas a separate species, probably basedon Macpherson (1961) and personalcommunications with Neil Smith. Anadult Thayer's Gull banded on 27August 1962 at Cambridge Bay,Victoria Island was observed 58 dayslater in Vancouver, British Columbia.It was seen several times at the citydump from 24 October to 6November 1962, when observationswere discontinued. Remarkably, theobserver read the band number witha telescope! Most Thayer's Gullswinter on the West Coast fromBritish Columbia to San Francisco.

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18. Sutton (1968) was the first topublish a skeptical review ofSmith's (1966) study. George M.Sutton was an eminent ornitholo­gist who knew Thayer's andKumlien's Gulls in the Arctic. In hiscarefully worded review, Suttonwrote: "Smith's findings concerning'super-eye-ringed' Thayer's Gullsperplex and discomfort me. In onebreath he asks us to believe that thesuccess of a gull's whole reproduc­tive cycle depends on eyesight keenenough to keep it from wastingeffort on a gull of opposite sexwhich does not have precisely thesame eyelid colour as its own, andthat this same gull will be fooledinto considering a big black circle asan 'eyelid', an eye as a 'pupil', etc."Sutton further stated: "His findings... are intensely interesting to specu­late upon whether they be consid­ered conclusive or not."

19. Andrle (1969) listed five speci­mens of Thayer's Gull from theNiagara Frontier Region, includingthe first specimen (first winter)taken in 1945 that was originallyidentified as L.g. kumlieni. InDecember 1967, three Thayer's(two adults and one second winter)were collected in the gorge of theNiagara River below the powerdams. Andrle (1969) said: "The 1967specimens might also be consideredthe first three for the Province ofOntario because these birds fre­quently flew back and forth acrossthe International Boundary before

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being collected on the UnitedStates side, and they probably wereretrieved from the Canadian por­tion of the river." We now knowthat the Niagara River is one of thebest places in eastern NorthAmerica, south of the Arctic, to seeThayer's Gulls.

20. 1. R. Jehl and B. A. Smith (1970)treated Thayer's Gull as a fullspecies. Jehl was one of the reviewersof Neal Smith's (1966) monograph.Jehl and Smith's book has an excel­lent photograph of an adult Thayer'sGull, and text on separating it fromHerring and Kumlien's Gulls. Theyalso mentioned two immature speci­mens of thayeri from Churchill in theNational Museum of Canada thatwere originally identified as L.g.kumlieni by Taverner and Sutton,once again illustrating the confusionbetween the two forms. They alsodescribe "one call-note of thayeri,given both by flying and foragingbirds, that is distinctly deeper-pitchedthan the comparable note of argenta­tus." I saw my first Thayer's Gulls in1970 at Churchill, Manitoba.

21. The ADU (1973) gave Thayer'sGull full species status based onMacpherson (1961) who showedthat smithsonianus and thayeri bredsympatrically without interbreed­ing, and Smith (1966) who reportedkumlieni and thayeri breeding sym­patrically. Until this decision,Thayer's Gull was regarded as asubspecies of the Herring Gull. Thiswas the turning point. Thayer's Gull

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was now official as a distinct species.Birders were now looking for thismythical gull and seeing it every­where! Interestingly, we wouldknow much less about Thayer's Gulltoday had the ADU not given it fullspecies status in 1973.

22. On 11 November 1973, I found afirst winter Thayer's Gull in Hull,Quebec near Ottawa. RichardPoulin of the National Museum(CMN 59224) collected it on 19November 1973, and Earl Godfreyconfirmed its identification. Thisspecimen was the first record forQuebec. The specimen of L.a. thay­eri listed for Tadousac, Quebec byDwight (1917) and the AOU (1957)was re-identified as L.a. smithsoni­anus with a Thayer's-like wing pat­tern (Earl Godfrey, pers. comm.).Ottawa area birders soon becamefamiliar with the field marks ofThayer's, finding them regularly insmall numbers afterwards. Duringthe 1970s a large series of Thayer's,Kumlien's and intermediate birdswas collected at Ottawa area dumpsby the National Museum, and uponanalysis, Earl Godfrey began tohave doubts about the validity ofThayer's Gull as a separate species.

23. Gosselin and David (1975) pub­lished the most detailed descriptionof Thayer's Gull to date with pho­tographs in American Birds. Nowbirders had more field marks, andThayer's Gulls were seen every­where!

24. Lehman (1980) wrote a compre­hensive article in Birding on theidentification of Thayer's Gull, withexcellent photographs and illustra­tions of all ages. Birders had morefield marks, and the sightingsincreased across North America.

25. Weber (1981) in a taxonomicreview concluded that the Iceland­Kumlien's-Thayer's complex form­ed a single polytypic species.

26. Gaston and Decker (1985) ofthe Canadian Wildlife Servicereported random interbreedingbetween Thayer's and Kumlien'sphenotypes on Southampton Islandin northern Hudson Bay. Theyreported a mix of light and darkeyed gulls, with varying wingtip pig­mentation and patterns.

27. Grant (1986) revised his classicgull guide of 1983 and it nowincluded North American species.Thayer's Gull was treated as a fullspecies following the AOD (1973,1983). Based on information fromone Nova Scotia birder, Grantincorrectly said that Kumlien'sIceland Gull is not variable, when infact it is extremely variable. Thiswrong information added to theconfusion.

28. In the revised edition of TheBirds of Canada, Godfrey (1986)treated Thayer's Gull as a sub­species of the Iceland Gull. Godfreysaid: "Studies made by Brian

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Knudsen for the National Museumof Natural Sciences in summers of1975 and 1976 at Home Bay, BaffinIsland (where in 1961 thayeri andkumlieni were thought by N.G.Smith [1966 Ornithological Mono­graphs 4] to breed sympatricallywith no observed interbreeding)produced no evidence of assorta­tive mating of the morphs but indi­cated instead an area of widespreadinterbreeding among the pheno­types of these two taxa. Additionalreasons for treating thayeri here asa subspecies of L. glaucoidesinclude abundant specimen evi­dence from widely separated locali­ties that colour and pattern differ­ences between thayeri and kumlieniare completely bridged by individ­ual variation." Godfrey's book hascolour illustrations on Plate 36 byJohn Crosby of all three subspecies:glaucoides, kumlieni and thayeri. Inaddition, there is an illustration byS.D. MacDonald on page 264 show­ing the variation in the pattern andpigmentation in the primaries, rang­ing from pale extreme to averageadult Thayer's.

29. DeBenedictis (1987), in a com­mentary on Gaston and Decker(1985) [incorrectly cited as A.I.Canaster and R. Zecher], statedthat: "This paper may mark thebeginning of the end of thayeri as aspecies."

30. Snell (1989, 1991) found non­assortative breeding between

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Kumlien's and Thayer's Gulls atHome Bay, Baffin Island. He refut­ed the assortative mating of thayeriand kumlieni reported by Smith(1966). Snell assessed the logisticaldifficulties of Smith setting upexperiments, collecting data andtravelling long distances betweenstudy sites in the Arctic, concludingthat it was impossible for Smith tohave completed all the work report­ed. He stated that Smith's method­ology and conclusions should beviewed cautiously.

31. DeBenedictis (1990) traced thehistory of Thayer's Gull. He statedthat his article "might well havebeen subtitled the 'rise and fall ofThayer's Gull'." DeBenedictis dis­cussed the studies of Macpherson(1961), Smith (1966, 1967), and howSnell (1989) tried to replicate someof Smith's experiments, "given thecontrary results that subsequentinvestigators had reported". Heconcluded: "I think that it is time toaccept the consensus of Canadianornithologists and reduce thayeri toa subspecies of the Iceland Gull ...like kumlieni".

32. Gaston and Elliot (1990)described a colony of Kumlien'sGulls on Coats Island in northernHudson Bay, which Smith (1966)previously identified as Thayer'sGulls. This is a good example of theconfusion that existed and stillexists about the appearance ofthese two taxa.

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33. Sibley and Monroe (1990) treat­ed Thayer's as a subspecies of theIceland Gull. They stated that"kumlieni appears intermediatebetween glaucoides and thayeri, allthese forms constituting one contin­uum of breeding populations repre­senting a single species". They alsocited Richard C. Banks who "sug­gests that kumlieni (and thayeri) is adistinct polymorphic species moreclosely related to argentatus than toglaucoides". Richard Banks is thecurrent chair of the AODCommittee on Classification andNomenclature. Interestingly, BurtL. Monroe, co-author listed above,was the previous chair of the ADDCommittee on Classification andNomenclature. Monroe died in1994. Considering that Sibley andMonroe (1990) treated Iceland,Kumlien's and Thayer's as con­specfic, I wonder if the recent ADDCheck-list (1998) would havelumped Thayer's with Iceland hadMonroe lived. Also of interest, thelate Charles C. Sibley was Neil G.Smith's PhD supervisor at Cornell,but he did not follow his former stu­dent I s conclusion in his book asstated above.

34. Zimmer (1990) provided adetailed treatment of the complex.He stated that "the problem ofidentifying Thayer's Gull has notgone away; it has become evenmore difficult" because "these gullsare confusingly variable". The pres­ence or absence of pigmentation on

the sixth primary arbitrarily dividesadult Thayer's and Kumlien'saccording to Zimmer.

35. Smith (1991) replied to Snell(1989) and to the earlier review bySutton (1968). Smith agreed thatthere were some errors in his study,but claimed that they did not affecthis findings and conclusions. I high­ly recommend that you read thetwo papers by Snell (1989, 1991),and Smith's (1991) reply inColonial Waterbirds.

36. Zimmer (1991) had 19 pho­tographs showing the tremendousrange of variation in Iceland Gullsfrom Newfoundland, including sev­eral probable kumlieni x thayeriintergrades. The photo in Figure 14shows four birds (three adults andone third winter); one bird haswhite wingtips, one bird has blackwingtips, and the third and fourthbirds are intermediate! Zimmeragain arbitrarily separatedKumlien's and Thayer's by the pig­mentation on the sixth primary.Southern Ontario birders also areaware of the incredible variation inIceland Gulls, ranging from adultswith pure white wingtips and clearyellow eyes to birds with blackwingtips and dark eyes.

37. James (1991) treated thayeri as asubspecies of the Iceland Gull, fol­lowing Godfrey (1986) and sup­ported by a large series of speci­mens in the Royal Ontario Museum.

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38. The British Ornithologists'Union (1991) treated Thayer's Gullas a subspecies of the Iceland Gull.

39. Snell and Godfrey (1991) pre­sented their findings at the AOUmeeting in Montreal. They said:"Iceland Gulls (Larus glaucoides)form a poorly understood and taxo­nomically controversial speciescomplex. We analysed patterns ofgeographic variation among 317museum specimens of adults col­lected throughout the breedingrange of Greenland to Banks Islandin the western Canadian arctic arch­ipelago. Although east-west clinalincreases in degree of mantlemelanism, primary feathermelanism, primary pattern score,and bill size are significant, there issubstantial overlap in all charactersamong geographic regions. There isno evidence that any of the threesubspecies (L.g. glaucoides, L.g.kumlieni, and L.g. thayeri) are mor­phologically discrete. Type speci­mens of kumlieni and thayeri (thetype of nominate glaucoides is notextant) are simply points within cli­nal continua, rather than exemplarsof differentiated groups." RichardSnell is of the "new school" of tax­onomists. He considers the Iceland­Kumlien's-Thayer's cline to repre­sent one highly variable species withno subspecies. Earl Godfrey is of the"traditional school" of taxonomists,believing that dividing the threeforms into subspecies is a very use­ful way of sorting the populations.

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40. Pittaway (1992) treated Thayer'sas a subspecies of the Iceland Gullfollowing Godfrey (1986) and James(1991). I often accompanied RichardPoulin of the National Museum tocollect gulls at Ottawa area dumps.Seeing the fresh specimens in thehand and the wide degree of overlapbetween Iceland and Thayer's Gullsmade me realize that they comprisedone variable species.

41. Weir et al. (1995) reported on aninvasion of Iceland Gulls that werekilled by an oil spill at the BritishShetland Islands in 1993. The adultspecimens examined clearly demon­strated a glaucoides-kumlieni cline.

42. The video by Vanderpoel (1997)on The Large Gulls of NorthAmerica, like Grant's classic guide, isa milestone in gull identification. Itincludes excellent footage and discus­sion of Thayer's and Iceland Gulls.

43. The AOD (1998) currentlyregards Thayer's Gull as a fullspecies. The decision to give speciesstatus to Thayer's Gull in 1973 wasbased primarily on Smith (1966).The conclusions and methodologyof Smith's study are now widelytreated with skepticism based oninformation from Sutton (1968),Godfrey (1986), Snell (1989),DeBenedictis (1990), Snell andGodfrey (1991), Snell (1991), BOD(1991) and others. The AOD contin­ues to disregard this information.Finally, the AOD (1998) says that

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Thayer's Gull "is now generallyregarded as a distinct species". Tothe contrary, many of the authori­ties cited in this article do not con­sider Thayer's Gull a distinctspecies.

44. Beaman and Madge (1998)regard Thayer's as a race of theIceland Gull.

45. Howell (1999) gave a conciseoverview of the Thayer's debate. Ifound myself agreeing with most ofhis points. He questioned theAOD's (1998) statement thatThayer's "is now generally regardedas a distinct species", by pointingout that most recent non-AOD lit­erature treats Thayer's Gull as asubspecies of the Iceland Gull.

46. Michel Gosselin (in litt.) of theCanadian Museum of Nature hasmade a careful study of 80 adultbreeding specimens and additionalwinter adults of Thayer's-Kumlien'sin the museum. His examinationincluded measurements, primarypigmentation and pattern, andmantle colour. Gosselin arbitrarilyconsidered as pure Thayer's, adultbirds with five or more dark tippedprimaries, occurring north or westof Home Bay, Baffin Island. Dsing aprinter's grey scale (0 =white, 100 =black), he found that mantle colourtaken from the small upperwingcoverts ranged from 45 to 55 inThayer's (n = 57, mean = 50) andfrom 30 to 50 in Kumlien's (n =21,

mean = 38). He stated that themean of nominate Iceland is proba­bly around 30. The shade of thedarkest wingtip markings rangedfrom 62 to 75 in Thayer's (n = 54,mean = 69) and from 35 to 70 inKumlien's (n = 19, mean = 44).Gosselin concluded: "Given thegreat variability of Kumlien's Gull,its intermediate appearance, andthe intermediate position of itsbreeding and wintering grounds, Ifirmly believe that Kumlien' s Gullis an intergrade populationbetween Iceland and Thayer's."

47. Richard Snell (in prep.) is doingthe account of the Iceland Gull forThe Birds of North America series.Based on his field work and museumstudies, Snell (pers. comm.) will treatThayer's Gull as a form of theIceland Gull. Since Iceland Gull wasthe first described of the three taxa, itwill become the name of the species.

ConclusionThe published and specimen evi­dence clearly indicate that Thayer'sGull is not a distinct biologicalspecies. The "new school" of taxon­omists, such as Richard Snell, treatsThayer's as part of the Iceland Gullcomplex, but would not give it sub­species ranking because its clinalcharacters vary geographically atdifferent rates and in differentdirections. I recommend followingthe traditional treatment of

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Godfrey (1986) that lists three sub­species of the Iceland Gull: nomi­nate L. g. glaucoides, L. g. kumlieni,and L. g. thayeri. The two approach­es used by Snell and Godfrey arenot incompatible. We could classifyIceland Gulls as Type I (glaucoides­like), Type II (kumlieni-like) and·Type III (thayeri-like). Regardlessof how we classify them, they are nomore or less identifiable in the field.The AOD is bound to change itsposition as more authors indepen­dently adopt a taxonomy recogniz­ing that Thayer's is a form of theIceland Gull.

AcknowledgementsI greatly appreciate comments onthe first draft by Earl Godfrey,Michel Gosselin, Jean Iron, RichardSnell and Ron Tozer. I also thankMichel Gosselin, Allen Hale, TonyLang, Ron Scovell, Ron Tozer andChip Weseloh, who helped melocate critical references. Over theyears, I have had many interestingdiscussions with birders andornithologists about Thayer's Gulls,including the late Harold Axtell,Rick Blom, Glenn Coady, BobCurry, Willie D'Anna, Bruce DiLabio, Rob Dobos, Earl Godfrey,Michel Gosselin, Brian Henshaw,Jean Iron, Alvaro Jaramillo, BruceMactavish, Kevin McLaughlin, thelate Henri Ouellet, Richard Poulin,Richard Snell, Ron Tozer and AlanWormington.

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Ron Pittaway, Box 619, Minden, Ontario KOM 2KO

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