Presumed Hybrids of the Herring Gull and the Great Black-Backed Gull

has seen such hybrids misidentffied as martnusandfuscus (tentatively), in both casesthe lighting was dull and the only Presumed hybrids of the other speciespresent was argentatus However, under ideal conditions the paler mantle, heavier bill, larger s•ze, Herring Gull and the and eye-ringcolor (whenyellow) should Great Black-backed Gull- preventconfusion with fuscus. Conversely, observersidentifyingfuscus with whitish or pinkishlegs should ensure always that a newproblem of identification the bird is similar in size to argentatus, the bill more slender,and the eye-ring R ogerA. Foxall red. In addition the streakingabout the head and neck of typical wmter- plumaged fuscus is reddish-brownand spoton the ninth. The legcolor is whitish relatively heavy. Similarly under ideal BSERVERSthe northeasternINEASTERN UnitedCANADA Statesand or very pale flesh. The colorsof the iris conditionsthe other possibleconfusions shouldbe aware of the increasingnum- and eye-ringare various shadesof yel- can be avoided. The mantle is too dark ber of apparenthybrids of Herring Gull low. The streakingabout the head and and the size too great for most of the (Larus argentatus) and Great Black- neckis variablebut alwaysmarkedly less subspeciesof argentatusthat have nonce- backed Gull (Z. marinus). These birds intense and more restricted than that of ably darker mantles than L. a. smtthso- could be misidentifledby the unwary as typicalwinter-plum aged argentatus. nianus (L. a. atlantis, barabensis, cach- the paler race of the Lesser Black- innans, michahellis, mongolicus,tatmy- backed Gull (Z. Jhscusgraellsii), dark HESPECIMEN COLLECTED at Ottawa rensis,vegae). L. a. heugliniis largerand mantied subspeciesof L. argentatus, differs from the above only in that much darker mantled than L. a. smtth- Western Gull fL. occidentalis)or by the there is virtually no subterminalwhite sonianusbut the leg coloris yellow InL very ambitious as Slaty-backedGull (L. spotin the ninth primaryand thereis no occidentalis the mantle is darker, the schistisagus). streakingabout the head and neck. As usuallydark, the eye-ringyellow, and the The first North Americanspecimen of far as can be ascertained in the field, the white in the outer primariesis restricted a presumed argentatus X marinus Ottawa sightrecords are of very similar to the tenth. L. schistisagushas a much hybridwas collectedby Jehl,January 10, birds also, with one significantexcep- darkermantle and a red eye-ring. 1959 at Staten Island, New York (Jehl, tion. The eye-ring of the 1973 bird In conclusion, observers in eastern 1960). Sincethen specimenshave been appeareddark and that of the 1974 bird Canada and the northeastern United taken at Kingston,Ontario January 12, (whichmay havebeen the samebird) was Statesshould be awareof thesepresumed 1967 (Godfrey, 1973); on the Niagara seenclearly to be bright red. hybrids,take particularcare in the •den- River December 5, 1970 (Andde, 1972) It seemsstrange that, with the excep- tiffcation of any dark mantled Land and November 22, 1971 (Andde, 1973); tion of the first record, all the records other than marinus, and should make an and at Ottawa, Ontario, September25, are from Ottawa or the lower Great effort to contribute to the scarce avail- 1974 (spec. in Nat'l Mus. of Nat. Sci., Lakes. All records occurred in the fall or able data regarding these hybrids by Ottawa). In addition there have been winter seasons.Obviously more informa- attemptingto determinetheir source sight records of similar individuals on tion is needed on the occurrence of these The author is grateful to Dr. W E the Niagara River in 1968 and 1969 birds and their distribution. Observers Godfrey,Curator, Ornithology, National (Andrle, 1973) and at Ottawa November shouldnot only report all sightingsof Museum of Natural Sciences, Ottawa, 23-28, 1972 (seeGodfrey, 1973), Novem- such birds, but also look for mixed col- for his constructive criticism of this arti- ber 11-24, 1973 (both by Ron Pittaway onies to determine their source. cle andfor supplyinga detaileddescrip- and the author) and November 16-23, The occurrenceof thesebirds will pose tion of the specimencollected in Ottawa 1974 by Richard Poulin, Ron Pittaway, an identificationproblem for observers Literature Cited and the author. unaware of their existence. The com- All the specimensdescribed in the lit- bination of characteristics described ANDRLE, R. F. 1972. Another probable erature bear a striking resemblanceto above is sufficientlydifferent from that hybridof Larus marinusand L. argentatus one another. All are adult females. In of those specieswith which it may be Auk 89 (3): 669-671. 1973.A secondprobable hybrid of Larus confused so that, under ideal conditions, each case the mantle color, body size, marinusand L. argentatuson the Niagara and wing. bill and tarsusmeasurements experiencedobservers should realize that River. Can. FieM-Nat. 87 (2): 170-171. are intermediatebetween those of argen- sucha bird is somethingdifferent. How- GODFREY, W. E. 1973. More presumed tatus and marinus (for measurements ever, some of the characteristics are dif- hybrid gulls: Larus argentams X L marin us. Can. Field-Nat. 87(2):171-172 summary,see Godfrey, 1973). The man- ficult to determinein the field and judg- JEHL, L R., Jr. 1960. A probablehybrid of tle color of each is described as close to ment of size,mantle color, and bill pro- Larus argentatus and L. marinus. Auk 77 "neutral gray" of Ridgway(1912). The portionsmay dependupon which species (3):343-345. primary pattern is slightlyvariable but are present for comparison.Although RIDGWAY, R. 1912. Color standards and consistsbasically of a long subterminal the mantle color is somewhatpaler than color nomenclature.Pub. by the author Washington,D.C. white spot on the tenth (terminal in the that ofL. f graellsii,poor lighting condi- New York specimen) with a shorter tions can make the mantle appearmuch --587 DuJf Crescent,Ottawa, Ontarto, (about half as long) subterminalwhite darker,particularly in flight. The author Canada K1J 7C6.

838 AmericanBirds, November 1979