OTTO FRENGEN PETER W. POST Figure 1. Breeding pair of L. f. fuscus in typical definitive alternate Figure 2. Typical example of intermedius from the west coast plumage. Note the even blackish color of the back and wings of Sweden. The back and wings are lighter than in fuscus, and the relative lack of contrast with the black primaries, the small and the contrast with the black primaries is therefore greater. white primary spots, the long wings with the tip of the tail opposite Hållo, Bohuslän Province, Sweden. 16 July 1992. or falling short of the fourth primary tip, and the relatively long yellow legs. Horsvaer, northern Norway. June 1986.

ROGER TIDMAN ROBERT H. LEWIS Figure 3. A typical graellsii. The shade of gray, and the contrast with Figure 4. A Dutch intergrade (intermedius × graellsii) showing the the black primaries, precludes this bird from ever being mistaken for mantle and wing–color characteristic of the majority of Lesser any other subspecies of L. fuscus, despite the small size of the white Black-backed Gulls breeding in the Netherlands. Maasvlakte, primary tips caused by wear. Northumberland, England. June 1982. Rotterdam. 16 July 1994.

282 BIRDING. AUGUST 1995 The Lesser Black-backed Gull in the Americas Occurrence and Subspecific Identity Part I: Taxonomy, Distribution, and Migration

cently been discovered breeding in 1950 to 1994. Sight and speci­ PETER W. POST * † Greenland (Boertmann 1994), and men records continued to accu­ and ROBERT H. LEWIS † one, mated to a Herring Gull, was mulate at a slow rate from 1950 found breeding in southern until the mid-1970s, when the Gull watching is one of the Alaska (van Vliet et al. 1993). number of reports per year be­ most challenging and rewarding gan to rise noticeably, if not ex­ aspects of birding. This is no Discovery ponentially. By the 1980s, L. fus­ doubt due in part to the large and Expansion cus had been recorded from all population of gulls, the ease with in the New World of eastern and central Canada which they can be observed, the 1850 to 1949. The first North and from all the Great Lakes subtle identification challenges American records of Lesser states and along the entire Atlan­ they present, and the exciting Black-backed Gull consist of tic and Gulf coasts of the US. possibility of finding a wanderer specimens collected in Greenland As of the first half of 1994, from another coast or continent. in 1850 (Boertmann 1994; Table Lesser Black-backed Gulls have For much of the past forty 1) and on 15 April 1920 (Salo­ been reported in all 31 states and years, one of the most eagerly monsen 1967; Table 1). The first the District of Columbia in the sought prizes in the northeastern bird reported for North America eastern half of the United States, US and eastern Canada has outside Greenland was an indi­ except for West Virginia (De­ been the Lesser Black-backed vidual seen on 9 September 1934 Sante and Pyle 1986; White 1990; Gull (Larus fuscus) of northern at Beach Haven, Ocean County, Hall 1993; Stedman 1994). In the and western Europe. But in the New Jersey (Edwards 1935). Great Plains states it has oc­ last two decades, this species has This record was followed by curred once in North Dakota undergone a continent-wide ex­ eight reports of birds from the (Martin 1991) and three times in pansion and is no longer re­ coastal New York City and New Nebraska (Silcock and Roche stricted to the Northeast, nor Jersey area in the late 1930s and 1994), and at least one bird has even in the New World to the 1940s (Kuerzi and Kuerzi 1935; occurred annually since 1984 in US and Canada. The total num­ Elliott 1940; Cruickshank 1942; Oklahoma (Newall 1984; J.A. ber of Lesser Black-backed Gulls Alexander 1946), a 1938 report Grzybowski, pers. comm.). Far­ seen on the National Audubon from Key West, Florida (Sprunt ther west it has occurred at least Society Christmas Bird Counts 1938), a 1948 specimen from thirteen times in Colorado has been increasing every year Maryland (Buckalew 1950; Ta­ (Webb and Conry 1978; R. and is still increasing, ln fact, the ble 1), a 1948 record from Indi­ Knight, pers. comm.), once in Lesser Black-backed Gull has re­ ana (Brock 1979), which is the Utah (Kingery 1991), and six earliest inland record for North times in California (Binford *141 West 73rd Street, New York, New America, and a 1949 specimen 1978; Small 1994). There are also York 10023-2917 † 176 Hunter Avenue, North Tarrytown, from upstate New York (Beard­ three acceptable records from New York 10591-1315 slee and Mitchell 1965; Table 1). southeastern Alaska (Gibson and

TAXONOMY. DISTRIBUTION, AND MIGRATION 283 Lesser Black-backed Gull

Kessel 1992; T.G. Tobish, pers. list (1983), Lesser Black-backed ton 1988a; Raffaele 1989), St. comm.), including a specimen Gulls winter regularly in small Croix (Norton 1986), Antigua (Gibson and Kessel 1992; numbers in North America from (Norton 1988b), Aruba (Voous Table 1) and a bird found mated the Great Lakes region, Labra­ 1977, 1983), St. Martin (Voous to a Herring Gull near Juneau in dor, eastern Québec, and New­ and Koelers 1967; Voous 1983), 1993 (van Vliet et al. 1993). foundland, south to Florida and Trinidad (ffrench 1991), Tobago In Canada, L. fuscus has been along the Gulf coast west to (ffrench 1991), Mexico (Howell recorded in all ten provinces and Texas. The first report of Lesser and Webb 1995), Venezuela (Alt­ in the Northwest Territories (De- Black-backed Gulls on a Christ­ man and Swift 1989), Guyana Sante and Pyle 1986; White mas Bird Count (one each from (D. Finch and A. Maley, pers. 1990). Although regular well in­ New York and Kings counties, comm.), French Guiana land in southern Ontario, it is New York) was during the 1962– (Devillers 1979), and on the Pa­ still casual in the Prairie Prov­ 1963 season (Cruickshank 1963). cific coasts of Panama (Smith inces: it has occurred about four Thirty years later, the 1992–1993 1982) and Costa Rica (S. times in southern Manitoba in counts (including count week) re­ Perkins, pers. comm.). ln addi­ the Winnipeg area (P. Taylor, corded 160 individual Lesser tion to the birds that come from pers. comm.) and four or five Black-backed Gulls on 86 counts the northern Palearctic, it is also times in northern Manitoba at in three Canadian provinces, likely that some birds directly Churchill (P. Benham, J. Schulen­ twenty-one states, and the Dis­ cross the Atlantic to the south­ berg, and P. Taylor, pers. trict of Columbia (Le Baron eastern US and the Caribbean comm.), five or six times in Sas­ 1993). One hundred forty-three from southern Europe or the Af­ katchewan (R. Kreba, pers. of these birds were found from rican coast. comm.), and about four to six Newfoundland on the Atlantic An “immature” gull collected times, with only one confirmed, seaboard to Texas on the Gulf in Argentina on 26 March 1931 in Alberta (P. Sherrington, pers. coast, eleven in the Midwest and identified by Robert Cush­ comm.). It has occurred twice in (Ohio, Michigan, Indiana, Illi­ man Murphy as a Lesser Black- British Columbia (Campbell nois, Iowa), one in Kentucky, backed Gull (Steullet and Deau- 1990; Siddle 1994). The first Ca­ one in Tennessee, and three in tier 1939) may be an example of nadian record was at Churchill Bermuda. The largest number of Olrog’s Gull, L. (belcheri) atlan­ in 1968 (Godfrey 1986). individuals recorded were from ticus (Narosky, pers. comm.). Ron D. Weir and Ron Ridout New York to North Carolina The specimen is extant (N.A. have provided a table detailing (100) and in Florida (9), latitudes Bó, pers. comm.) and needs to be the explosive increase of reports equivalent to the main wintering reexamined. in Ontario from 1977 to 1993 areas in the Old World. Maximum numbers of L. fus­ (Table 2). Tove (1989) provides An early analysis of North cus seen in a single day include: a similarly dramatic chart for American Lesser Black-backed 11 from the Chesapeake Bay North Carolina and South Caro­ Gull records by Webb and Conry Bridge and Tunnel, Virginia, 26 lina, and, indeed, comparable ta­ (1978) indicated that “some indi­ October 1985 (R.D. Barber, bles could probably be prepared viduals migrate through the US, pers. comm.); 31 at Cape Point for many states and provinces perhaps to winter farther south on the North Carolina Outer bordering the Atlantic Ocean, along the coasts of Mexico, Cen­ Banks, 28 January 1995 (E.S. the Great Lakes, and the Gulf of tral and South America, and in Brinkley, pers. comm.); 35 at the Mexico. The Lesser Black- the Caribbean Islands”. Indeed, Pompano landfill, Pompano, backed Gull is recorded regularly to the south of the US, there are Florida, 10 April 1993 [although in Greenland, where it is also in­ reports of L. fuscus (although the published report (Langridge creasing. The species occurs regu­ many of these lack any details) 1993) states these last birds were larly in Bermuda (Amos 1991). from Abaco in the Bahamas all “immatures” ,according to According to the AOU Check­ (Norton 1994), Puerto Rico (Nor­ the observer about a dozen were

284 BIRDING. AUGUST 1995 part I

adults, the rest first- and second- summer birds, were at Hart- Gull (L. argentatus) group is ex­ year birds (A. Wormington, pers. Miller Island, Maryland, 20–31 tremely complex. For the pur­ comm.)]; and 40 at Penn Manor July 1992 (Armistead 1992). poses of this article we follow Lakes and landfill, Bucks Grant (1986), who treats L. fus­ County, Pennsylvania, 5 January Taxonomy cus as a separate species consist­ 1994 (Brinkley et al. 1994). ln The taxonomy of the Lesser ing of three subspecies, L. f. summer, up to 19, mostly first- Black-backed (L. fuscus) / Herring graellsii, L. f. intermedius, and

Table 1 NEW WORLD SPECIMENS AND BANDING RECOVERY OF LESSER BLACK-BACKED GULL, THROUGH 1993

Location Date Disposition Age and Sex Reference Nanor Talik, Greenland 1850 ZMUC #65272 adult Boertmann 1994; Boertmann, pers. comm. Qôrnoq (Qoornoq), Godthåb District, 15 April 1920 ZMUC #65271 adult male Salomonsen 1967; Preuss, pers. comm. Greenland Godthåb, Godthåb District, Greenland (see 1 June 1961 banded as young, Salomonsen 1967, 1971; Boertmann, pers. text) “not yet flying” comm.; Preuss, pers. comm. Faeroe Islands 1958 Faro Segunda Barranca, south of Bay of San 26 March 1931 Museo de la Plata, #6366, La female immature Steullet and Deautier 1939; Nelly A. Bó, pers. Blas, Buenos Aires, Argentina (see text) Plata R., Argentina comm.; Preuss, pers. comm. Assateague Island, Worcester Co., Maryland 7 October 1948 USNM #421801 adult female Buckalew 1950; J. P. Angle, pers. comm. S. Buffalo, Erie County, New York 14 March 1949 BSNS #4084 adult female Beardslee and Mitchell 1965 near Rutherford, Bergen County, New Jersey 9 February 1958 AMNH #468815 adult female Jehl 1958 near Morocco, Newton County, Indiana 9 April 1962 USNM #532341 adult female Mumford and Rowe 1963; Angle, pers. comm. Fresh Pond, St. Martin, Lesser Antilles 13 January 1966 ZMA #18733 first-year female Voous 1967, 1977; Prins, pers. comm. Castle Harbor, Bermuda 10 November 1969 BAM #B444 Wingate adult female Wingate, pers. comm. Courtney Campbell Causeway, Tampa, 22 February 1971 ABS #4440 Woolfenden adult male G.W. Woolfenden and R.W. Schreiber 1974; Hillsborough County, Florida Woolfenden, pers. comm. St. George Island, Franklin County, Honda 9 July 1974 TTRS#3277 second-summer male H.M. Stevenson 1975 Toytown Landfill, St. Petersburg, Pinellas 26 February 1983 ABS #240 Hoffman first-winter male S.R. Patton, pers. comm.; County, Florida G.W. Woolfenden, pers. comm. Saddlebunch Keys, Monroe County, Florida 13 December 1987 ABS #257 Hoffman adult female G.W. Woolfenden, pers. comm. near old mouth Mermentau River, Cameron 25 September 1985 LSUMZ #126705 second-winter S.W. Cardiff, pers. comm. Parish, Louisiana female near old mouth Mermentau River, Cameron 6 October 1985 LSUMZ #126707 male, molting from S.W. Cardiff, pers. comm. Parish, Louisiana third-summer to adult winter near old mouth Mermentau River, Cameron 10 November 1985 LSUMZ #126706 female, adult S.W. Cardiff, pers. comm. Parish, Louisiana summer, molting to winter Beauharnois Dam, Québec 3 December 1977 NMC #65883 adult female M. Gosselin, pers. comm. Nepean Dump, Ottawa, Ontario 20 October 1983 NMC #78726 adult male M. Gosselin, pers. comm. Nepean Dump, Ottawa, Ontario 21 October 1983 NMC #78727 adult female M. Gosselin, pers. comm. Nepean Dump, Ottawa, Ontario 28 October 1983 NMC #78728 adult female M. Gosselin, pers. comm. Nepean Dump, Ottawa, Ontario 1 November 1983 NMC #78729 adult male M. Gosselin, pers. comm. j Nepean Dump, Onawa, Ontario 8 November 1983 NMC #78734 adult male M. Gosselin, pers. comm. Nepean Dump, Onawa, Ontario 15 November 1983 NMC #78735 adult male M. Gosselin, pers. comm. Nepean Dump, Ottawa, Ontario 30 November 1983 NMC #78736 adult female M. Gosselin, pers. comm. Nepean Dump, Onawa, Ontario 24 April 1984 NMC #84184 adult male M. Gosselin, pers. comm. Nepean Dump, Onawa, Ontario 26 September 1984 NMC #84185 adult male M. Gosselin, pers. comm. Nepean Dump, Ottawa, Ontario 4 October 1984 NMC #84186 adult male M. Gosselin, pers. comm. Nepean Dump, Onawa, Ontario 22 October 1984 NMC #93831 adult male M. Gosselin, pers. comm. Lemon Creek, Juneau, Alaska 19 September 1990 UAM #5708 adult female Gibson and Kessel 1992 Abbreviations: ABS = Archbold Biological Station, Lake Placid, Florida; AMNH = American Museum of Natural History, New York; BAM = Bermuda Aquarium, Museum; BSNS = Buffalo Society of Natural Sciences, Buffalo, New York; LSUMZ = Louisiana State University Museum of Natural Science, Baton Rouge; NMC = National Museum of Canada (Canadian Museum of Nature), Ottawa; TTRS = Tall Timbers Research Station, Tallahassee, Florida; UAM = University of Alaska Museum, Fairbanks; USNM = United States National Museum, Washington, DC; ZMA = Zoological Museum, University of Amsterdam, Amsterdam; ZMUC = Zoological Museum, University of Copenhagen. All the specimens listed (except for the unknown identity of Florida specimens ABS#240 and ABS#257) have been identified as graellsii. Number 257, however, is also probably graellsii because its mantle, except for being less worn and not as brown, matches that of #4440 identified as graellsii by E. Eisenmann (G.E. Woolfenden, pers. comm.).______

TAXONOMY. DISTRIBUTION, AND MIGRATION 285 Lesser Black-backed Gull

L. f. fuscus (Figures 1–3). Birds to distinguish among the subspe­ cent years the Netherlands has of the Western Palearctic cies. According to Ryttman et al. been colonized by graellsii from (Cramp and Simmons 1983) and (1978), however, this feature is the west and intermedius from the Handbuch der Vogel Mit­ of “limited” taxonomic value in the northeast (see Distribution teleuropas (Glutz von Blotzheim this regard. Barth’s studies were and Migration in the Old World and Bauer 1982) also consider largely overlooked at first, at below), and large-scale inter­ two Eurasian forms that Grant least in North America. It was breeding is blurring the distinc­ (1986) considers subspecies of only with the publication of the tion between the two forms (Fig­ the Herring Gull to be Lesser books by Grant (1982, 1986) and ure 4). In fact, Spaans (1979) felt Black-backed Gulls —one of Harrison (1983, 1985) that inter­ that interbreeding had pro­ which may have occurred in medius received wide recogni­ gressed to the point where the North America. A specimen be­ tion. If fuscus is elevated to spe­ subspecific identification of lieved to be L. argentatus cific status, then, if Sibley and Dutch birds (described in Part 11) taimyrensis was taken in Alaska Monroe (1993) are followed, was no longer possible. in 1921 (Bailey 1948). It is pre­ graellsii and intermedius will be sumably the basis for the Alaska known as the “Dark-backed record of Lesser Black-backed Distribution Gull” and fuscus will continue to and Migration Gull cited in the sixth edition be known as the Lesser Black- in the Old World of the AOU Check-list. The backed Gull. specimen needs to be reex­ L. f. graellsii breeds in the It needs to be stressed that amined. The other form, L. a. Faeroes and the British Isles. In Barth’s work was based on speci­ heuglini, has never been re­ the late 1920s, this subspecies mens from the British Isles, the corded in North America to our colonized Iceland, recolonized Faeroes, Finland, and Scandina­ knowledge. France, and colonized the Neth­ via, and on only two old speci­ Although intermedius was first erlands and Germany. It was mens from the Netherlands. The described in 1922, until fairly re­ first found breeding in Denmark latter were obtained when graell­ cently most authorities did not about 1940 (Olsen 1992) and in sii was a rare breeding bird in recognize it as a valid subspecies Portugal and northwestern Spain the Netherlands, and inter­ of L. fuscus. A reexamination of in the 1970s (Cramp and Sim­ this question by Voous (1963), medius was only a visitor. In re­ mons 1983). L. f. intermedius and especially by Barth (1966, Table 2 1967a, 1968, 1975a, 1975b), dem­ RECORDS OF LESSER BLACK-BACKED GULL IN ONTARIO onstrated the validity of inter­ Year Spring Summer Fall Winter Summer medius. Differences among the 0 0 1 0 1 three subspecies are based pri­ 1978 0 0 2 0 2 marily on bill and wing length, 1979 0 0 2 0 2 mantle color, molt, and migra­ 1980 0 0 8 0 8 1981 0 0 4 0 4 tion patterns, ln all these charac­ 1982 3 0 5 8 16 teristics, except back and wing 1983 3 1 24 6 34 color, intermedius and graellsii 1984 7 1 25 6 39 are more similar to each other 1985 6 0 13 5 24 1986 13 1 25 8 47 than they are to fuscus. These 1987 13 2 17 16 48 and other differences, such as dif­ 1988 22 9 29 13 73 ferences in feeding ecology, have 1989 25 7 40 17 89 led some authors to suggest that 1990 24 4 26 19 73 1991 28 3 34 18 83 fuscus may be a distinct species 1992 20 6 39 27 92 (Strann and Vader 1992). Barth 1993 21 2 42 17 82 (1967b) also used egg dimensions Totals 185 36 336 160 717

286 BIRDING. AUGUST 1995 part I

breeds in southern Norway, From their breeding grounds (Edelstam and Ramel 1956; southwestern Sweden, and Den­ in Scandinavia, intermedius mi­ Preuss and Harild 1980; Glutz mark, and spread south to the grate south, overland, across con­ von Blotzheim and Bauer 1982; Netherlands in the late 1960s tinental Europe to the Mediterra­ Kilpi and Saurola 1984). Most (Rijsdijk 1968; Spaans 1979). L. nean (Preuss and Harild 1980), birds continue to the Persian f. fuscus breeds in northern Nor­ or southwest, to winter in the Gulf and to the Arabian and Red way, southeastern Denmark, same areas as graellsii (Edelstam seas. Some individuals continue eastern Sweden, Finland, and and Ramel 1956; Glutz von south to Mozambique (Urban et northwestern Russia. Birds at­ Blotzheim and Bauer 1982; Kvin­ al. 1986) and occasionally south tributable to one subspecies occa­ nesland and Munkejord 1984). It to Natal and the Transvaal in sionally breed within the range is also the most abundant subspe­ South Africa. of another; birds whose mantle cies in southeastern England dur­ Many nominate fuscus mi­ color is typical grate down the of intermedius Nile and Rift have been valleys as far as found breeding Zambia and in England, Malawi, to and all three winter on East subspecies have African lakes. been found in Some move the same breed­ west from the ing colony in Rift Valley as Denmark far as western (Barth 1966). Zaire. Banded Recoveries of birds recovered birds banded in from the West Great Britain African coast (Harris 1962; presumably ar­ Baker 1980), rived via this the Faeroes route rather (Preuss and than south Harild 1980; along the At­ Jensen and lantic coast of Fritze 1991), RICHARD BOWEN northwestern Iceland and Figure 5. An apparent intermedius Lesser Black-backed Gull at the Africa. Move­ France (Cramp Pompano Landfill, Broward County, Florida, 10 March 1990. This represents ment of L. f. one of only a few documented records of this subspecies for North America. and Simmons Note the even blackish color of the back and wings, fuscus to the 1983), and the and the contrast with the black primaries. west and south­ Netherlands west is excep­ (Speek and Speek 1984) show ing the non-breeding season tional. Through 1978, for exam­ that graellsii winter mainly along (Davenport 1985). ple, there had been only five re­ the Atlantic coast of Iberia and Nominate fuscus migrates coveries of fuscus from the Neth­ northwestern Africa, extending overland from its breeding erlands (de Heer 1981). south to Senegal, and occasion­ grounds to the south and south­ Furthermore, some of these ally to Sierra Leone and Nigeria. east, across central and eastern birds, which were banded as A few individuals are found in Europe to the Black and Caspian chicks in mixed colonies, may the western Mediterranean as far seas, and to the Mediterranean have been misidentified Herring east as Italy and Tunisia. as far west as Italy and Algeria Gulls (see Voous 1963).

TAXONOMY. DISTRIBUTION, AND MIGRATION 287 Lesser Black-backed Gull

The populations of both graell­ sii (Kuerzi and Kuerzi 1935)! Be­ At present there is no conclu­ sii (Cramp and Simmons 1983) cause intermedius was not gener­ sive evidence that nominate fus­ and intermedius (Røv 1986) have ally recognized at the time, and cus has occurred in the New generally increased in recent this is the more likely of the Scan­ World. Although fuscus mi­ years, while that of fuscus has dinavian forms to occur in grates to the south and southeast greatly declined throughout its North America, we believe that from its breeding grounds, it is range. L. f. fuscus is now gener­ these birds were possibly inter­ possible that a bird that had ally considered threatened in medius, although the Florida crossed from East Africa to the northern Norway (Strann and bird could have been fuscus. The Gulf of Guinea could continue Vader 1992). A 1986 report men­ backs or mantles of three of west to the New World. The re­ tions only about 500 pairs breed­ these individuals were reported cent substantial decline in the ing in Finland compared to 1800 to match those of the Great numbers of this subspecies, how­ pairs in the 1950s (European Black-backed Gulls they were ever, make the likelihood of this News, 1986), and the total Swed­ with (Edwards 1935, Elliott happening slim. ish population, which was esti­ 1940), a description that strongly The subspecies graellsii ex­ mated at about 17 000 pairs in supports intermedius. panded its breeding range to Ice­ the late seventies, had dwindled Dark-mantled Lesser Black- land between 1920 and 1930 to about 4000–5000 pairs in 1990 backed Gulls reported to be the (Gudmundsson 1955) and is ap­ (T. Tyrberg, pers. comm.). subspecies fuscus are occasion­ parently still increasing there. On the basis of population, ally seen in eastern North Amer­ Thus, it has generally been as­ breeding distribution, and migra­ ica (see Part II). Most, if not all sumed that all the Lesser Black- tory patterns, we would expect of these, are probably inter­ backed Gulls that occur in graellsii to occur in North Amer­ medius or Dutch intergrades. Of North America originate in Ice­ ica, with perhaps some inter­ the eighty or so Lesser Black- land (e.g. Cramp and Simmons medius. ln contrast, fuscus backed Gulls seen by the second 1983). This belief, of course, ig­ would be extremely rare, if it oc­ curred at all. author in the Carolinas, two nores sight-record and photo­ were almost certainly inter­ graphic evidence that birds of medius (Lewis 1980, Tove 1989). Distribution the Scandinavian subspecies in­ in the New World Of the sixty-three observed by termedius have occurred in Bruce Peterjohn in Ohio, only North America, and the possible For more than thirty years the one exhibited characteristics of existence of one or more breed­ common wisdom has been that intermedius (B.G. Peterjohn, all Lesser Black-backed Gulls ing populations of graellsii in seen in North America are mem­ pers. comm.). northern Canada. The first bers of the subspecies graellsii. It is useful to look at the ratio of North American records from This assumption is supported by graellsii to intermedius Lesser Greenland were in 1850 and the fact that all of the North Black-backed Gulls wintering in 1920, before the species was American specimens identified to southern Portugal, which has the known to breed in Iceland, and subspecies have been graellsii same latitude as southern Vir­ the one New World banding re­ (Table 1). Although the vast ma­ ginia. The second author’s field covery, also from Greenland, jority of sight records has also in­ work there during two winters in­ was of a bird hatched on the volved graellsii, there is evidence dicates graellsii outnumbers inter­ Faeroes (Salomonsen 1967, 1971; that intermedius has also oc­ medius by at least one hundred to Table 1). curred (Figure 5 and front cover; one. Assuming that in a typical If Lesser Black-backed Gulls see also Part II). winter there are a few hundred are breeding in the New World, Intriguingly and paradoxi­ Lesser Black-backed Gulls in east­ numbers have to be substantial cally, six of the seven initial sight ern North America and that most to account for the number of in­ records from 1934 to 1940 were of them come from Western dividuals seen here. Could a sub­ reported to be fuscus (Edwards Europe, then, extrapolating from stantial number of Lesser Black- 1935; Sprunt 1938; Elliott 1940; the Portugal figures, it might be backed Gulls be breeding in the Cruickshank 1942). Only one of reasonable to expect a few inter­ vast expanse of the far north? these birds was assigned to graell­ medius among them. Thus far, the only confirmed

288 BIRDING. AUGUST 1995 part I breeding of this species in North Altman, A. and B. Swift. 1989. Checklist 1983. The Birds of the Western America consists of single pairs of the Birds of South America. 2dn cd. Palearctic, v.3. New York: Oxford Uni­ Great Barrington, Massachusetts. Pri­ veritys Press. in Greenland in 1990, 1991, and vately Printed. Cruickshank, A. D. 1942. Birds Around 1992, with others suspected, in­ American Ornithologists’ Union. 1983. New York City. New York. American cluding at least eight additional Check-list of North American Birds. Museum of Natural History. pairs in 1992 (Boertmann 1994), 6th ed. ———. ed. 1963. The sixty-third Christ­ Amos, J.R.E. 1991. A Guide to the Birds mas Bird Count. Audubon Field Notes, and a bird mated to a Herring of Bermuda. Pembroke, Bermuda: Ber­ 17: 61–296. Gull found breeding in southeast­ muda Press. Davenport, L.J. 1985. British status of ern Alaska in 1993 (van Vliet et Armistead, H.T. 1992. Middle Atlantic northern Lesser Black-backed Gulls. al. 1993). A juvenal-plumaged Coast region. American Birds, 46: 1129. British Birds, 78: 668–669. Lesser Black-backed Gull at Bailey, A.M. 1948. Birds of Alaska. Denver: de Heer, P. 1981. Over status van Baltis­ Colorado Museum of Natural History. che Kleine Mantelmeeuw in Nederland Long Point, Ontario, on the Baker, R.R. 1980. The significance of the (On the status of the Baltic Lesser early date of 28 July (Ridout Lesser Black-backed Gull to models of Black-backed Gull in the Netherlands). 1993) may have been hatched in bird migration. Bird Study, 27: 41–-50. Dutch Birding, 3: 55. North America. The appearance Barth, E.K. 1966. Mantle colour as a taxo­ DeSante, D. and P. Pyle. 1986. Distribu­ nomic feature in Larus argentatus and tional Checklist of North American of other juveniles as early as 18 Larus fuscus. Nytt Magasin for Zoologi, Birds. v. 1. Lee Vining, California: August in southern Ontario 13: 56–82. Artemisia Press. (Weir 1989) and 6 September in ———. 1967a. Standard body measure­ Devillers, P. 1979. Un Goéland brun Massachusetts (S. Perkins, pers. ments in Larus argentatus, L. fuscus, L. (Larus fuscus) en Guyane française. comm.) does not prove breeding canus, and L. marinus. Nytt Magasin Gerfaut, 69: 79–80. for Zoologi, 14: 7–83. Edelstam, C. and C. Ramel. 1956. Fåglar­ in North America, because there ———. 1967b. Egg dimensions and laying nas Flyttning (The Migration of Birds). are large numbers of fully dates of Larus marinus, L. argentatus, Stockholm: Norstedts. fledged juveniles in the Nether­ L. fuscus and L. canus. Nytt Magasin Edwards, J.L. 1935. The Lesser Black- lands by 15 July, and birds of the for Zoologi, 15: 5–34. backed Gull in New Jersey. Auk, 52: 85. ———. 1968. The circumpolar systemat­ Elliott, J. 1940. Scandinavian Lesser Black- year banded in Britain have been ics of Larus argentatus and Larus fus­ backed Gull on Long Island. Proceed­ recovered in Spain and Portugal cus, with special reference to the Nor­ ings of the Linnaean Society of New during August. wegian populations. Nytt Magasin for York, 50/51: 34–35. A more thorough analysis of Zoologi, 15(supplement 1): 1–50. European News. 1986. British Birds, 79: distribution based on past and fu­ ———. 1975a. Moult and taxonomy of the 284–292. Herring Gull Larus argentatus and the ffrench, R. 1991. A Guide to the Birds of ture New World Lesser Black- Lesser Black-backed Gull L. fuscus in Trinidad and Tobago. 4th ed. Ithaca: backed Gull records would be northwestern Europe. Ibis, 117:384 –387. Cornell University Press. valuable. Unfortunately, but per­ ———. 1975b. Taxonomy of Larus argen­ Gibson, D.D. and B. Kessel. 1992. Sev­ haps inevitably, attending the in­ tatus and Larus fuscus in north-western enty-four new avian taxa documented Europe. Ornis Scandinavica, 6: 49–63. in Alaska. Condor, 94: 454–467. crease of reports in Lesser Black- Beardslee, C.S. and H.D. Mitchell. 1965. Glutz von Blotzheim, U.N. and K.M. backed Gulls in recent years has Birds of the Niagara Frontier Region. Bauer. eds. 1982. Handbuch der Vogel been a lessening of interest in the Bulletin of the Buffalo Society of Natu­ Mitteleuropas. Band 8. Wiesbaden, Ger­ species. There exists an almost ral Sciences, No. 22. many: Akademische Verlagsgellschaft. Binford, L.C. 1978. Lesser Black-backed Godfrey, W.E. 1986. The Birds of Can­ “ho-hum another Lesser” atti­ Gull in California, with notes on field ada. rev. ed. Ottawa: National Muse­ tude. We submit that this is a se­ identification. Western Birds, 9: 141–150. ums of Canada. rious error. Every effort should Boertmann, D. 1994. An annotated check­ Grant, P.J. 1982. Gulls: A Guide to Identi­ be made to assess the subspecific list of the birds of Greenland. Meddelel­ fication. Vermillion, South Dakota: and changing status of this spe­ ser om Grønland, Bioscience, 38: 1–63. Buteo Books. Brinkley, E.S., W.J. Boyle, Jr., R.O. Pax­ ———. 1986. Gulls: A Guide to Identifica­ cies in the New World. The in­ ton and D.A. Cutler. 1994. Middle At­ tion. 2dn ed. Vermillion, South Dakota: crease in numbers presents an op­ lantic Coast region. National Audubon Buteo Books. portunity to critically identify Society Field Notes, 48: 185–192. Gudmundsson, F. 1955. Íslenzkir fuglar the distribution and movements Brock, K.J. 1979. Birdlife of the Michigan XII. Sílamáfur (Larus fuscus) (Icelandic City area, Indiana. Indiana Audubon Birds XII. The Lesser Blackback (Larus of a fascinating species as it pos­ Quarterly, 57: 94–113. fuscus)). Náttúrufraedingurinn, sibly colonizes another continent. Buckalew, J.H. 1950. Records from the Del- 25: 215–226. Mar-Va Peninsula. Auk, 67: 250–252. Hall, G.A. 1993. Appalachian region. Campbell, R.W. 1990. The Birds of Brit­ American Birds, 47: 256–258. References ish Columbia, v.2. Victoria: Royal Brit­ Harris, M.P. 1962. Migration of the Brit­ Alexander, H.G. 1946. Lesser Black-backed ish Columbia Museum. ish Lesser Black-backed Gull as shown Gull in New York harbor. Auk, 63: 258. Cramp, S. and K.E.L. Simmons. eds. by ringing data. Bird Study, 9: 174–182.

TAXONOMY. DISTRIBUTION, AND MIGRATION 289 Lesser Black-backed Gull

Harrison, P. 1983. Seabirds: An Identifica­ Fugle ringmaerket i Denmark 1964— Stedman, S. 1994. Central Southern re­ tion Guide. Boston: Houghton Mifflin. 1968 (Birds ringed in Denmark 1964— gion. National Audubon Society Field ———. 1985. Seabirds: An Identification 1968). Copenhagen: Copenhagen Notes, 48: 215–218. Guide. rev. ed. Boston: Houghton Zoological Museum. Steullet, A.B. and E.A. Deautier. 1939. Mifflin. Raffaele, H.A. 1989. A Guide to the Birds of Sobre la Presencia de Larus fuscus y Howell, S.N.G., and S. Webb, 1995. A Puerto Rico and the Virgin Islands, rev. Speotyto cunicularia juninensis en la Ar­ Guide to the Birds of Mexico and ed. Princeton: Princeton University Press. gentina. Notas del Museo de la Plata, 4, Northern Central America. New York: Ridout, R. 1993. Ontario region. Ameri­ Zoologia, No. 21: 245–249. Oxford University Press. can Birds, 47: 1104–1106. Strann, K.-B. and W. Vader. 1992. The Jensen, J.-K., and E. Fritze. 1991. Farøske Rijsdijk, K. 1968. Tweedc bekende nominate Lesser Black-backed Gull Larus Sildemågcrs (Larus fuscus graellsii) broedgeval van Larus fuscus inter­ fuscus fuscus, a gull with a tern-like feed­ traek (The migration of Faeroes Lesser medius in Nederland (Second known ing biology, and its recent decrease in Black-backed Gulls (Larus fuscus breeding occurrence of Larus fuscus in­ northern Norway. Ardea, 80: 133–142. graellsii)). MTR Interne Meddelelser termedius in the Netherlands). Limosa, Stevenson, H.M. 1975. Lesser Black- Til Zoologisk Museums Ringmaerkere, 41: 153. backed Gull summering in Florida. Flor­ 90: 6–7. Ryttman, H., H. Tegelström, and H. ida Field Naturalist, 3: 22. Kilpi, M. and P. Saurola. 1984. Migration Jansson. 1978. Egg dimensions of Her­ Tove, M. 1989. Reappraisal of the status of and wintering strategies of juvenile and ring Gulls Larus argentatus and Lesser gulls in the Carolinas. Chat, 53: 53–63. adult Larus marinus, L. argentatus and Black-backed Gulls L. fuscus. Ibis, 120: Urban, E.K., C.H. Fry and S. Keith. eds. L. fuscus from Finland. Ornis Fennica, 353–356. 1986. The Birds of Africa, v.3. New 61: 1–8. Røv, N. 1986. Bestandsforhold hos York: Academic Press. Kingery, H.E. 1991. Mountain West re­ sildemåkc (Larus fuscus) i Norge med van Vliet, G., B. Marshall, D. Craig and gion. American Birds, 45: 296–299. hovedvekt på L. f. fuscus (The breeding J. Egolf. 1993. First record of nesting ac­ Kuerzi, J. and R. Kuerzi. 1935. Occur­ population of Lesser Black-backed Gull tivity by a Lesser Black-backed Gull rence of Lesser Black-backed Gull Larus fuscus in Norway, with emphasis (Larus fuscus) in North America. Pa­ (Larus fuscus graellsi [sic]) in Bronx on L. f. fuscus). Vår Fuglefauna, 9: 79–84. cific Seabird Group Bulletin, 20: 21. County, New York City. Proceedings of Salomonsen, F. 1967. Fuglene på Grøn­ Voous, K.H. 1963. Geographic variation the Linnaean Society of New York, land (The Birds of Greenland) .Copen­ of Larus fuscus in northwestern 45/46: 101–102. hagen: Rhodos. (For an English transla­ Europe. Ardea, 51: 16–24. Kvinnesland, A. and A. Munkejord. tion of the seabird chapters by R.G.B. ———. 1977. Northern gulls in Aruba, 1984. Sildemåkene fra Vestlandet trek- Brown, sec The Seabirds of Greenland. Netherlands Antilles. Ardea, 65: 80–82. ker direkte over Nordsjøen (Lesser Canadian Wildlife Service Report No. ———. 1983. Birds of the Netherlands Black-backed Gulls from west Nor­ 100, 1 June 1981.) Antilles. 2dn cd. Zutphen, Netherlands: way migrate across the North Sea). ———. 1971. Recoveries in Greenland of De Walburg Pers. Vår Fuglefauna 7 : 91–93. birds ringed abroad. Meddelelser om Voous, K.H. and H.J. Koelers. 1967. Langridge, H.P. 1993. Florida region. Grønland, 91: 1–52. Check-list of the birds of St. Martin, Saba, American Birds, 47: 406–408. Sibley, C.G. and B.L. Monroe, Jr. 1993. and St. Eustatius. Ardea, 55: 115–137. Le Baron, G.S. ed. 1993. The ninety-third A Supplement to Distribution and Tax­ Webb, B.E. and J.A. Conry. 1978. First Christmas Bird Count. American Birds, onomy of Birds of the World. New Ha­ record of a Lesser Black-backed Gull in 47: 473–1028. ven: Yale University Press. Colorado. Western Birds, 9: 171–173. Lewis, B. 1980. Lesser Black-backed Gull Siddle, C. 1994. British Columbia / Yukon Weir, R. D. 1989. Ontario region. Ameri­ in the Carolinas. Chat, 44: 79–81. region. American Birds, 48: 142–144. can Birds, 43: 94–99. Martin, R. 1991. Northern Great Plains Silcock, W.R. and R.R. Roche. 1994. White, A. 1990. List of North American region. American Birds, 45: 288–290. Winter field report, Dec 1993–Feb 1994. Birds. Bethesda, Maryland: Bird Com­ Mumford, R.E. and W.S. Rowe. 1963. Nebraska Bird Review, 62: 51–63. mander. The Lesser Black-backed Gull in Indi­ Small, A. 1994. California Birds: Their Woolfenden, G.E. and R.W. Schreiber. ana. Wilson Bulletin, 75: 93. Status and Distribution. Vista, Califor­ 1974. Lesser Black-backed Gulls in Flor­ Newall, J.G. 1984. A new bird for Okla­ nia: Ibis Publishing Company. ida. Florida Field Naturalist, 2: 20–21. homa: Lesser Black-backed Gull. Bulle­ Smith, N.G. 1982. Lesser Black-backed Gull tin of the Oklahoma Ornithological So­ in Panama. American Birds, 36:336 –337. ciety, 17: 17–20. Spaans, A.L. 1979. Kleine Mantelmeeuw Norton, R.L. 1986. West Indies region. Larus fuscus (Lesser Black-backed Gull American Birds, 40: 528–529. Larus fuscus). In: R.M. Teixeira, ed. ———. 1988a. West Indies region. Ameri­ Atlas van de Nederlandse Broedvogels can Birds, 42: 327–328. (Atlas of the Breeding Birds of the Neth­ ———. 1988b. West Indies region. Ameri­ erlands). ’s-Graveland, the Netherlands: can Birds, 42: 485–486. Natuurmonumenten. ———. 1994. West Indies region. National Speek, B. J., and G. Speck. 1984. Thieme’s Audubon Society Field Notes, 48: 252–254. Vogeltrekatlas (Thieme’s Atlas of Bird Olsen, K.M. 1992. Danmarks Fugle— en Migration). Zutphen, Netherlands: oversigt (Birds of Denmark—a check­ Thieme. list). Copenhagen: Dansk Ornithologisk Sprunt, A. Jr. 1938. Scandinavian Lesser Forenig. Black-backed Gull at Key West, Flor­ Preuss, N.O., and P.A. Harild. 1980. ida. Auk, 55: 671–672.

290 BIRDING. AUGUST 1995 Figure 1. A definitive basic (winter) plumaged L. f. graellsii with Herring Gulls for comparison at the Chesapeake Bay Bridge and Tunnel, Virginia, 26 October 1985. Note the back and wing color and targe white primary tips. The amount of head streaking is less than in most basic-plumaged graellsii. DANIEL R HEATHCOATE

Figure 2. Typical example of L. f. fuscus taken on the wintering grounds at Eilat, Israel, Spring 1988. Note the even blackish color of the back and wings, small white primary tips, relatively long wings, and slender bill.

HADORAM SHIRIHAI

Figure 3. Adult L.f. intermedius (left) with L f. graellsii and Yellow-legged Gulls (L cachinnans; upper right) for comparison, photographed at Lagos, Portugal, 9 January 1994. Note the length of the wing extension beyond the tail (the fourth primary tip is in line with the tip of the tail). Compare the wing length and dark even color of the back and wings with that of the accompanying graellsii.

ROBERT H. LEWIS

370 BIRDING. OCTOBER 1995 Lesser Black-backed Gull in the Americas Occurrence and Subspecific Identity Part II: Field Identification

scribe adult birds — those in de­ Great Black-backed Gulls be­ PETER W. POST * †and finitive (fourth or later) basic cause of their more extensive ROBERT H. LEWIS † (winter) plumage— only, though dark head markings. And Lesser many of our comments also ap­ Black-backed Gulls are more like In Part 1, we presented an ply to third basic and to third Iceland Gulls (L. glaucoides) in overview of the taxonomy of the and definitive alternate (breed­ body proportions and wing Lesser Black-hacked Gull (Larus ing) plumages. Younger birds are length, having slender bodies fuscus) and provided a historical presumably not identifiable as to and relatively long and slender synopsis of its occurrence in subspecies until adult coloration wings. North America. The field identi­ begins to show on the mantle Adult Lesser Black-backed fication of Lesser Black-backed and scapulars in second basic Gulls have a red orbital ring Gulls is discussed by many (second-winter) and second alter­ and a pale yellow iris, as do authors, including Binford nate (second-summer) plumages. Great Black-backed Gulls. (1978), Glutz von Blotzheim and Adult Lesser Black-backed Bauer (1982), Cramp and Sim­ General Characteristics Gulls, however, have yellow mons (1983), Harrison (1983), ln a distant mixed flock of Great legs and feet, which vary indi­ Bruns (1983, 1988), Grant (1986), Black-backed (L. marinus) and vidually and seasonally in Urban et al. (1986), and De Herring (L. argentatus) Gulls, brightness; they can even be Schutter (1989). Identification of adult Lesser Black-backed Gulls bright orange at the beginning the three subspecies is discussed appear somewhat similar to the of the breeding season. Some in­ in detail by Cramp and Simmons Great Black-backed Gulls in dividuals have legs and feet that (1983) and Grant (1986). The fol­ back and wing color. As one gets have been described as fleshy, lowing discussion is based on closer to the birds, the paleness grayish, or cream. One must be these sources, examination of of L. f. graellsii becomes more careful, however, when dealing museum skins, and field experi­ obvious. In size Lessers are the with the colors of soft parts, es­ ence in North America, Europe, same or (usually) smaller than pecially with “apparent” adults and elsewhere. Herring Gulls. When seen in that actually may be “ad­ We assume reader familiarity flight from below, the primaries vanced” three-year-olds or “re­ with the four-year sequence of and secondaries of adult L. fus­ tarded” four-year-olds. Great plumages of large Larus gulls. cus (of all subspecies) are dusky Black-backed Gulls with yellow The basics are covered in Grant gray, as in Great Black-backed feet (Barth 1968) or orange legs (1986) and Wilds (1989). We de­ Gulls. The grayness of the lower (van Kreuningen 1980; de Heer surface of these feathers con­ 1981) have been reported from * 141 West 73rd Street, New York. New trasts with the white of the un­ Europe. A small black-backed York 10023-2917 derwing coverts. † Department of Mathematics, Fordham gull with yellow legs reported University, Bronx, New York 10458 In winter, graellsii and inter­ from South Portland, Maine, in (e-mail: [email protected]) medius generally stand out from 1985, and identified as a Lesser

FIELD IDENTIFICATION OF LESSER BLACK-BACKED GULL 371 Lesser Black-backed Gull

Black-backed Gull, appears from picts a pale individual. Both Coloration the photographs to be a Great books imply, however, that there of Upperparts Black-backed Gull. Another are only two subspecies and de­ L. f. graellsii is the lightest of the Great Black-backed with yel­ pict only one, as do other guides three forms. Obviously much lowish legs was reported from (e.g. Farrand 1983), which only darker-mantled than the North Virginia Beach, Virginia, in Feb­ adds to the confusion. Plate 59 in American form of Herring Gull ruary 1995. Harrison (1983) is another fine il­ (L. a. smithsonianus; Figure 1), Although the back and wings lustration of graellsii. Photo­ darker than California Gull (L. of Lesser Black-backed Gulls graph number 455 in Harrison californicus), but much paler vary in the degree and shade of (1987) of an adult in flight, if, than Great Black-backed Gull, it black or gray, they are always indeed, it is a Lesser Black- does appear to be a “black- noticeably darker than those of backed Gull, is an astonishingly backed” gull in the field under Herring Gulls. Thus, Lessers pale individual. Harrison (1983, most light conditions. The man­ stand out as “black-backed 1985) is the only one of these tle and wings are a dull smoky gulls” .They are easily distin­ four guides to illustrate gray or ash gray rather than guished from Great Black- L. f. fuscus. blackish, with obvious contrast backed Gulls by their overall The painting of a breeding between the black wing-tip and shape, body size, bill, and usu­ adult L. f. fuscus (Plate 82, Fig­ the remainder of the wing and ally yellow legs. The bill of the ure 5) in Cramp and Simmons back. Some lighter-colored birds Lesser Black-backed Gull is (1983) is accurate, except that resemble the shade of gray of a slender with a sharp gonydeal the mantle should be slightly Laughing Gull (L. atricilla). angle, like that of a Herring blacker. As pointed out by Dav­ L. f. fuscus is the darkest of Gull, and unlike the deep mas­ enport (1985), however, the the three forms (Figure 2). Both sive bill and bulbous gonydeal non-breeding adult intermedius Grant (1986) and Cramp and angle of the Great Black- (Plate 82, Figure 6) is not repre­ Simmons (1983) state that the backed Gull. The Lesser’s bill is sentative of this subspecies. It is back and wings of fuscus are as also generally more brightly col­ much too pale, and we believe black or blacker than that of ored, and the red spot at the it is more typical of graellsii, as Great Black-backed Gull, show­ gonys is typically more oblong are the two subspecifically un­ ing “hardly any” contrast with in shape (Figure 1). identified adults depicted in the black wing-tip. Harrison flight on Plate 81. Further, all (1985) states that the “mantle, Depictions the adults pictured on Plate 82 scapulars, back and upper wings in the Literature look too much alike in bill and [of fuscus are] almost (emphasis Lesser Black-backed Gulls have body proportions. ours) black (as in [the] Great been frequently misrepresented The many photos in Grant Black-backed Gull …)”. Reflec­ in field guides and other bird (1986), though in black and tion measurements clearly show, books. The main problem has white, are excellent. Note that however, that the mantle color been the depiction or description numbers 264 and 269 depict L. f. of fuscus from northern Norway of the shade of mantle color as intermedius and L. cachinnans and the Baltic is markedly (em­ too dark or too light. Among re­ (Yellow-legged Gull). Number phasis ours) darker than that of cent illustrations, the depictions 268, which shows an example of Great Black-backed Gull, of L. f. graellsii on page 155 of L. f. graellsii also next to a Yel­ whereas that of intermedius the National Geographic Soci­ low-legged Gull, is underex­ from southern Norway is ety’s Field Guide to the Birds of posed. Both birds are too dark. slightly lighter than that of North America (1983, 1987) This is a prime example of the Great Black-backeds (Barth and on plate 37 of The Birds of problems one encounters when 1966). Indeed, the examples of Canada (Godfrey 1986) are ex­ trying to judge shades of gray fuscus the senior author saw cellent, although the latter de­ from photographs. breeding in southeastern Sweden

372 BIRDING. OCTOBER 1995 part II

Figure 4. An apparent L f. intermedius

(right) with a L f. graellsii (left)

and Herring Gulls for comparison,

photographed at the Pompano Landfill,

Broward County, Florida, on 10 March

1990. Note in these two examples

of L fuscus the difference in the back

and wing color, and the contrast

between the black primaries and the

remainder of the wing. Both birds

have yellow legs. The smaller bill

and body size and rounder head shape RICHARD BOWEN of the graellsii indicate it is probably were all noticeably blacker than although many intermedius from a female, whereas the larger bill the Great Black-backed Gulls Denmark and southwestern Swe­ and body size and more angular they were with. All of the Finn­ den are fully as dark as Great ish, Swedish, and Norwegian or­ Black-backeds (Barth 1966). head shape of the intermedius nithologists and birders with They do not look grayish as in whom we have talked and corre­ graellsii. The contrast between indicate it is probably a male. sponded agree that this is the the black wing-tip and the re­ The small white primary tips case throughout its range. It mainder of the wing is more pro­ should also be noted that the nounced than in fuscus. The dif­ in the graellsii are the result color of the upperparts of Great ference in upperpart color of wear. Black-backed Gulls does not between intermedius and fuscus show geographic variation; we is most evident on the upper were unable to detect differences back (mantle). L. f. intermedius among museum specimens from and especially L. f. fuscus often New York, England, and Scandi­ show a brownish cast to the navia. back and wings (Figure 5), as L. f. intermedius (Figures 3 does L. marinus, a result of fad­ and 4) may represent an inter­ ing that can best be seen during grade population between graell­ molt as a contrast between fresh sii and fuscus. It shows the great­ and old feathers. Indeed, fuscus est individual variation in mantle means brown in Latin.† color among the three subspecies The situation is further compli­ (Barth 1966). It needs to be cated by large numbers of Dutch stressed that Barth (1966, 1975b) intergrades. Since about 1960, found some overlap in mantle for example, a large colony of color, albeit slight, between Lesser Black-backed Gulls has graellsii and intermedius and be­ formed in the industrial and port tween intermedius and fuscus. areas west of Rotterdam, espe­ The back and wings of L. f. in­ cially on a man-made peninsula termedius are blackish, varying from slightly to clearly paler † “graellsii” does not mean “gray.” It refers to a than Great Black-backed Gulls, Portuguese duke.

FIELD IDENTIFICATION OF LESSER BLACK-BACKED GULL 373 Lesser Black-backed Gull

called Maas­ ing all along the North Sea coast vlakte. From need to be studied with modern about 2000 biostatistical techniques. Birds pairs of Lesser breeding in western Jutland Black-backed (Denmark), may, for example, Gulls in 1983 also be intergrades between the population graellsii and intermedius has exploded to (Olsen 1992). its present (1994) size of Wing Pattern about 20 000 In this paper we follow Grant pairs (P. de (1986) in ignoring the vestigial Knijff, pers. outermost primary and number­ comm.). The ing the primaries inward from colony contains the outermost large (first) pri­ both graellsii mary to the innermost (tenth) HADORAM SHIRIHAI and inter­ Figure 5. Same adult L f. fuscus as shown primary. medius, often in mixed pairs. in Figure 2, here showing the relationship L f. graellsii generally shows a between feather wear and the brown color This situation is typical of the en of the back and wings, which can be so larger white mirror and larger tire Dutch population of Lesser white tip on the outermost pri­ pronounced in fuscus. Those feathers Black-backed Gull, which is cur­ showing the most wear are brown, mary than do intermedius and whereas those feathers on the mantle rently estimated to consist of fuscus. Although there may be with the least amount of wear are grayer. 40 000 to 60 000 pairs (P. de some overlap, intermedius and Knijff, pers. comm.). Most of the fuscus generally show only one birds resemble the one shown in small white mirror and a very Figure 4, Part 1, taken at Maas­ small white tip to the outermost vlakte, falling between the clas­ primary (Figures 8 and 9). In a sic graellsii (Figure 3, Part I) and study of museum specimens, intermedius (Figure 2, Part I) in Hario (1986) found that the mantle color. The bird in Figure white mirror of the first primary 6 also seems to be of this type. extended into the white feather Furthermore, in eastern Eng­ tip in 18 percent of graellsii land, where Figure 7 was taken, (n = 40) and 14 percent of inter­ there are another estimated medius (n =42), but in only 3 per­ 20 000 breeding pairs of Lesser cent of fuscus (n= 37). Although Black-backed Gulls that have the Grant (1986) stated that graellsii same shades of gray back and also usually (emphasis ours) has wings as most of those Lesser a mirror on the second primary Black-backed Gulls found breed­ where fuscus has none, Hario ANTHONY F. AMOS ing in the Netherlands (P. de (1986), in the series he examined, Figure 6. This bird, photographed Knijff, pers. comm.). This find­ found only 51 percent of graellsii at Mustang Island, Nueces County, Texas, ing means that there is a large to have a mirror on the second on 14 March 1984, is possibly an intergrade of the type breeding population of Lesser Black- primary compared to 30 percent in the Netherlands. It is apparently not backed Gulls that do not fall of intermedius and 22 percent of quite dark enough to be intermedius, within the range of mantle color fuscus. It is not uncommon to though too dark to be graellsii. It is hard variation of either graellsii or in­ to see which primary tip falls opposite the see fuscus with no mirrors at all, end of the tail, though the white primary termedius as described by Barth. especially in individuals with ex­ tips themselves are small. Lesser Black-backed Gulls breed­ tensive feather wear.

374 BIRDING. OCTOBER 1995 part II

Figure 8. L. f. fuscus in flight, photographed in Helsinki, Finland, 11 June, showing the relative lack of contrast between the primaries and the remainder of the wing (this contrast is further reduced in this photograph because of the bright sunlight), the single white mirror on the outermost primary, and the relatively long and slender bill. ROGER TIDMAN Figure 7. This is a very dork graellsii, or probably a Dutch intergrade type, photographed at Norfolk, England, April 1992. Note the large white primary tips, which are characteristic of graellsii. Compare with Figure 4, Part I, and with Figure 15. URBAN OLSSON

ROBERT H. LEWIS Figure 10. Photograph of L. f. graellsii, at Lagos, Portugal, 9 January 1994, illustrating the wing pattern. Note the sharp, but zigzag, demarcation between the black portion of the primaries and the remainder of the wing and back. ROBERT H. LEWIS Figure 9. L. f. intermedius with wings outstretched, at Lagos, Portugal, 9 January 1994. Note how the black of the primaries blends imperceptibly into the mantle color. The small white primary tips are visible, as is the single primary mirror, found on only the outermost primary. The bird to the right is a graellsii or a Dutch intergrade.

FIELD IDENTIFICATION OF LESSER BLACK-BACKED GULL 375 Lesser Black-backed Gull

When seen well in flight from above, graellsii usually shows sharp contrast between the black of the primaries and the gray of the remainder of the wing and mantle. There is a clear line of demarcation (often zigzagged) between these two areas (Figure 10). Not all graellsii show this character, however, and it is often difficult to see clearly. Sometimes the sharp demarca­ tion is visible only on one or two primaries. Freshness of plumage may be a factor. In flight, inter­ medius and fuscus never show ROBERT H. LEWIS igureF 11. A dose-up of the intermedius shown in Figures 3 any line of demarcation. On and 9, photographed 9 January 1994 at Lagos, Portugal. perched birds, however, the con­ Compare this photograph with the birds pictured in Figures 7 trast between the black tips of and 15. All three are relatively dark birds, but this bird is not as gray; it is blacker. Also compare the size the outer primaries and the rest of the unworn white primary tips and the length of the wings of the wing in intermedius and in the three birds, ln this bird, the wings are extremely long, and the end of the tail reaches the tip of the fourth primary. fuscus is evident. When the wing ln the birds pictured in Figures 7 and 15 the unworn white is closed, the proximal portions primary tips are larger, and the tip of the tail reaches, of the primaries are hidden by or is near, the white tip of the third primary. other feathers. The white bound­ ary between these areas, formed by the white tips of the secondar­ ies and the tertial-crescent, may add to this perception of con­ trast (see “Coloration of Upper­ parts” above). On fully adult (definitive ba­ sic) birds in fresh plumage seen perched from the side, the white tips of the outermost primaries form a row of diamond-like- shaped spots resembling seg­ ments of a circle, which are smaller on intermedius and fus­ cus than on graellsii (Figures 11 and 12). But beware of worn or abraded feathers! Primary molt in both graellsii and intermedius

GREG W LASLEY is usually complete by early De­ Figure 12. A typical definitive basic (winter) plumaged cember (fuscus takes a bit graellsii, photographed at Mustang Island, Nueces County, longer; Cramp and Simmons Texas, on 14 February 1980. Note the gray back and wing color, large white primary tips with the end of the tail falling 1983), so the feathers are neat between the third and fourth tips, and heavily streaked head. and fresh through the winter

376 BIRDING. OCTOBER 1995 part II

gull-watching season. By May, Figure 13. Another apparent however, the white primary tips North American intermedius photographed at the Pompano are worn. See Figure 3, Part I, Landfill, Pompano, Broward and Photo 286 in Grant (1986) County, Florida on 10 March for a graellsii showing small 1990, the same day as the worn tips to the primaries. intermedius pictured in Figure 4 and Figure 5, Part I. If we allow Wing length provides another for the slight underexposure character for separating graellsii of this photograph, the mantle and intermedius. On a perched color is correct for intermedius. Also note the small size intermedius, the wings extend of the white primary tips, far enough beyond the tail so and the long wings that extend that the white tip of the fourth well beyond the tip of the tail. primary reaches, or extends be­ RICHARD BOWEN yond, the tip of the tail (Figures 3, 11, 13, and 14). In graellsii, the tip of the tail falls between the third and the fourth primary tip (Figure 12). The Dutch inter­ grades are most like graellsii in this feature (Figure 4, Part I; Fig­ ures 7 and 15), although some of the dark gray birds show the fourth tip in line with the end of the tail.

Head Streaking PETER W. POST The head in all three forms is Figure 14. Another probable North American L. f. intermedius, at Point white in definitive alternate Lookout, Nassau County, New York, 28 September 1985 (immediately plumage. In definitive basic following Hurricane Gloria). Compare the size and shape of the Lesser Black-backed Gull with that of the Great Black-backed Gull and the Herring plumage, the heads of graellsii Gulls. Note the small size (probably a female), long wings and generally and intermedius become exten­ attenuated shape, thin long bill, and yellow legs. Although part sively streaked and washed with of the wing is in shadow, there appears to be little contrast dusky, particularly around the between the primaries and the rest of the wing. The mantle color, which is the same as that of the accompanying Great rear of the crown and the eye, Black-backed, matches that of intermedius and these markings may extend from the west coast of Sweden down across the lower throat (Figure 2, Part I). The mantle and upper breast. L. f. fuscus, of fuscus would be darker than that of a Great Figure 15. This individual, however, has a much whiter Black-backed photographed at Lagos, Portugal, head. When streaks occur on the Gull. 9 January 1994, is similar in color latter, they are restricted to the to the graellsii or intergrade taken rear of the crown and hindneck. on the breeding grounds in England Post-breeding adult graellsii and shown in Figure 7. Compare the size intermedius generally acquire of the unworn white primary tips of this bird with that of the intermedius shown head streaking in September, in Figure 3. Note that only three primary nominate fuscus in October tips extend clearly beyond the tail. Birds (Cramp and Simmons 1983). this dark are seen fairly regularly in North America; they are There is some indication that in­ almost certainly not termedius is usually less streaked ROBERT H. LEWIS intermedius.

FIELD IDENTIFICATION OF LESSER BLACK-BACKED GULL 377 Lesser Black-backed Gull

than graellsii and that the streaks sent a possible source of confu­ probable Herring × Lesser Black- do not form a central smudge sion. Although these birds are ex­ backed gulls along the east coast around the eye, but this needs tremely rare in nature,they do of the US. corroboration. Occasionally, vir­ occur. Foxall (1979) summarized Harris et al. (1978) believed tually unstreaked graellsii are and described four known speci­ that these hybrids could be con­ seen in winter (R.H. Lewis, mens and four sight records of fused in winter with individuals pers. obs.). From roughly Janu­ gulls presumed to be L. a. smith­ from one of the darker-backed ary on, breeding-plumaged sonianus × L. marinus hybrids Eurasian populations of Herring adults can be devoid of head from Ottawa, the lower Great Gull. One such species, the Yel­ streaks. Lakes, and New York, all seen low-legged Gull (L. cachinnans), or collected since 1959, pointing formerly considered by many Structure out possible confusion with L. authors to be a Herring Gull, L. f. graellsii is the largest of the fuscus, especially in poor light. but now generally considered to three forms. It also has the short­ In size and mantle color these be a separate species, has re­ est wings and a relatively short birds were intermediate between cently been recorded in North and thick bill. L. f. fuscus is the the parent species. The legs were America in Newfoundland, smallest form on average (only whitish or pale flesh in color, Québec, the Washington, DC – 76 percent the weight of graell­ and the orbital-ring was various Maryland area (Wilds and sii), has the longest wings, a slen­ shades of yellow or bright red. Czaplak 1994), and, probably, in der bill, and proportionately (In full breeding condition, Her­ North Carolina. longer legs. L. f. intermedius re­ ring Gulls have a yellow or yel­ As the common name implies, sembles graellsii in body propor­ low-orange orbital-ring; Lesser cachinnans also has yellow legs, tions (averaging 87 percent the Black-backeds have a red one.) but most populations are large weight of graellsii), but has Under ideal viewing conditions robust birds with ash-gray man­ longer wings and a longer and these hybrids can be told from tles (less bluish-gray than Her­ more slender bill (Cramp and Lesser Black-backed Gulls by ring Gull, less brownish-gray Simmons 1983). The measure­ their paler mantle, heavier bill, than Lesser Black-backed) that ments of graellsii and inter­ larger size, and orbital ring color are noticeably darker than a Her­ medius overlap, as do those of in­ (when yellow or orange), and a ring Gull’s, close to that of a termedius and fuscus. Some large white tip or mirror on the California Gull, but not nearly subtle jizz differences between outermost primary. as dark as that of L. f. graellsii. graellsii and intermedius can be Hybrids between Herring and In mid-winter the head is un­ at least tentatively suggested. In graellsii Lesser Black-backed streaked. From late summer to addition to being a bit longer Gulls resulting from cross-foster­ early winter there is some head and a bit more slender in overall ing experiments in England and streaking, usually most obvious body proportions, the head of in­ described by Harris et al. (1978) before the streaking on Herring termedius tends to be a bit were morphologically intermedi­ Gull and Lesser Black-backed rounder and the eye appears ate between the two species. The Gull is fully developed. The spe­ smaller and more centrally two individuals observed in the cies most closely resembles a placed. (Caution: Within a given field during the breeding season Herring Gull. Confusion with a gull taxon, females average were separable from Herring and Lesser Black-backed Gull is un­ smaller and rounder headed than Lesser Black-backed when on the likely (Figure 3; see also photo­ males.) ground, but not in flight, by a graph in Birding 1994, 26: 322). gray mantle midway in color be­ The field identification of this Hybrids tween the two species, pale yel­ species is discussed by Harris et Hybrid Herring × Great Black- low legs, and an orange-yellow al. (1989) and Wilds and backed gulls and Herring × orbital ring. There are a number Czaplak (1994). Lesser Black-backed gulls repre­ of additional sight records of Two probable hybrids be­

378 BIRDING. OCTOBER 1995 part II

tween Herring and intermedius pounded in photographs as a re­ every individual can be identi­ Lesser Black-backed gulls have sult of film type, age, and expo­ fied in the field. been described by Hansen (1960) sure. We have seen photographs • L. f. graellsii have a grayish mantle and Voous (1962). In both birds of the same bird that appear to that is clearly paler than that of any the mantle color matched “the be graellsii in one frame but in­ Great Black-backed Gull; it shows a lighter variants” of L. f. graellsii. termedius in another. Similarly, marked contrast with the black of They were large birds, and even legs and feet that are yellow in the outer primaries. (A bird with in breeding condition had “flesh­ life can appear flesh or pinkish the same mantle color as a Great Black-backed cannot be graellsii.) colored” legs or “gray feet with a in photographs (and in the field), graellsii have a bill that is similar to little yellow at the ankles and especially in early-morning and that of a Herring Gull and, from toes.” We know of no records of evening light. about September through January crosses between Herring and fus­ The two reports of L. f. fuscus or later, dusky head streaking. A cus Lesser Black-backed gulls, [= intermedius/ fuscus] published perched adult in fresh plumage (de­ and such birds are not likely to in The Birds of Canada (Godfrey finitive basic) shows medium to occur because of differences in 1986) illustrate some of the diffi­ large white primary tips. The end of breeding times between the two culties involved. “The Victoria Is­ the tail falls between the third and species (Barth 1968). land photo was taken in low, fourth primaries, but usually closer L. fuscus and L. cachinnans near-midnight arctic sunlight to the third. michahellis have recently ex­ and the yellow legs show as • L.f. intermedius have bill and body tended their ranges, so that they pink” (W.E. Godfrey, pers. shapes similar to graellsii, but have a now breed sympatrically in west­ comm.); the published descrip­ blackish mantle lighter than or ern France. Although mixed tion (Alsop and Jones 1973) is in­ equal to that of a Great Black- backed and showing some contrast pairs have been reported (Yésou sufficient to identify it to subspe­ with the black of the outer prima­ 1991), thus far no young are cies. “The [photograph of the] ries. Winter head-streaking is simi­ known to have been produced. Churchill bird is in black and lar in extent to graellsii but not as white. It is dark enough for fus­ heavy. A perched adult bird in Identification cus but the photographer fresh plumage (definitive basic) from Photographs thought it probably was graell­ shows very small white primary sii” (W.E. Godfrey, pers. Although “typical” individuals tips and wings extending well be­ comm.). In general, individuals of the three forms of Lesser yond the end of the tail, usually far in some photographs can be Black-backed Gull discussed in enough to have the fourth primary safely identified to subspecies, tip opposite, or beyond, the end of this paper can be distinguished particularly if other gull species the tail. in the field, the situation is com­ appear in the same frame as a ref­ • A Lesser Black-backed Gull can be plicated by intergradation be­ erence, and detailed field notes identified as fuscus only if it has a tween graellsii and intermedius are available. thin, long bill, a mantle darker than and intermedius and fuscus. Fur­ that of a Great Black-backed, wings thermore, the color of the mantle showing little contrast with the varies with lighting conditions Summary black of the outer primaries, long and the substrate upon which We review the range expansion pointed wings, only one small the bird is standing. With the and current distribution of the white mirror on the outermost pri­ sun behind the observer, the Lesser Black-backed Gull in the mary, a small, slender body, rela­ mantle looks darkest when the New World (Part I) and discuss tively long legs, and virtually no bird faces directly away. It is in­ the field identification of the head markings at any time of year. structive and more than a bit un­ three subspecies of Lesser Black- Although the more than thirty nerving to watch one’s suspected backed Gull —graellsii , inter­ specimens of L. fuscus collected intermedius rotate itself into just medius and fuscus (Part II). We in the New World have been another graellsii. offer criteria for differentiating identified as graellsii, we present These variables are com­ the subspecies, although not evidence that intermedius occurs

FIELD IDENTIFICATION OF LESSER BLACK-BACKED GULL 379 Lesser Black-backed Gull in North America (Cover Photo Nelly A. Bó, David Boertmann, Bill Bou­ References ton, Richard Bowen, Richard G.B. and Figure 5, Part I; Figures 4, 13 Alsop, F.J. III and E.T. Jones. 1973. Brown, Steven W. Cardiff, Arthur R. The Lesser Black-backed Gull in the and 14, Part II). There is no con­ Clark, Bruce M. Di Labio, Jon Dunn, Jon clusive evidence that fuscus has Canadian arctic. Canadian Field-Natu­ Fjeldså, A.D. Fox, Richard P. ffrench, ralist, 87: 61–62. occurred on this side of the At­ Daniel D. Gibson, U.N. Glutz von Barth, E.K. 1966. Mantle colour as a taxo­ lantic. Because of a serious de­ Blotzheim, Joseph A. Grzybowski, W. nomic feature in Larus argentatus and cline in its numbers, the prob­ Earl Godfrey, Michel Gosselin, Øyvind Larus fuscus. Nytt Magasin for Zoologi, Gjerde, Svein Haftorn, George A. Hall, 13: 56–82. ability of its occurring here in Martti Hario, M.P. Harris, Roger Hig­ the future is very low. ———. 1968. The circumpolar systematics son, J.P. Hubbard, the late M.E. Isleib, of Larus argentatus and Larus fuscus with The criteria used to separate Kaj Kampp, Mikael Kilpi, Hugh Kingery, special reference to the Norwegian popu­ the three subspecies of Lesser Nils Kjellen, Rudolf F. Koes, Rick Knight, lations. Nytt Magasin for Zoologi, 15 (sup­ Black-backed Gull need to be re­ Roger Kreba, David Lambeth, Lars Lars­ plement 1): 1–50. son, A. Maley, Phil Mattocks, Guy fined. Perhaps comparisons be­ ———. 1975b. Taxonomy of Larus argen­ McCaskie, Brad Millen, Aanen Munke­ tatus and Larus fuscus in north-western tween eye diameter and bill and jord, Tito Narosky, Duane Nelson, John Europe. Ornis Scandinavica, 6: 49–63. wing length, which led to the de­ G. Newell, Max Parker, Stephen R. Pat­ Binford, L.C. 1978. Lesser Black-backed velopment of objective criteria ton, Simon Perkins, Bruce G. Peterjohn, Gull in California, with notes on field for the field identification of Wayne R. Petersen, Galen L. Pittman, identification. Western Birds, 9: 141–150. Niels Otto Preuss, Tineke G. Prins, Johan­ Glaucous (L. hyperboreus) and Bruns, H. 1983. Heringsmöwe (Larus fuscus) nes Prüter, Robert L. Pyle, Ron Ridout, oder Mantelmöwe (Larus marinus)? Orni­ Iceland (L. glaucoides) gulls Tom Rogers, P. Sherrington, W. Ross Sil­ thologische Mitteilungen, 35: 311–315. (Grant and Mullarney 1989), cock, Ella Sorensen, Nils Røv, Karl-Birger ———. 1988. Zur feldornithologischen may prove useful with Lesser Strann, Chris Siddle, Don Smith, Dave Ste­ Unterscheidung unausgefarbter Her­ Black-backed Gull subspecies as jskal, the late Henry M. Stevenson, Nor­ ingsmöwen (Larus fuscus) u. Man­ man van Swelm, Peter Taylor, T.G. To­ telmöwcn (Larus marinus). Ornithologis­ well. bish, Jr., John L. Tveten, Tommy che Mitteilungen, 40: 215–220. Tyrberg, Gus van Vliet, K.H. Voous, Ron Cramp, S., and K.E.L. Simmons. eds. 1983. Acknowledgments D. Weir, S.O. Williams, David B. Win­ The Birds of the Western Palearctic. v.3. gate, Glen E. Woolfenden, and Richard New York: Oxford University Press. We thank the many photographers who Yank. Davenport, L.J. 1985. British status of trusted us with, and let us retain, their pre­ For help in translating papers in for­ northern Lesser Black-backed Gulls. Brit­ cious photographs for an inordinate eign languages we thank U.N. Glutz. von ish Birds, 78: 668–669. amount of time, many of whom also pro­ Blotzheim, Martti Hario, Peter Heerens, de Heer, P. 1981. On Great Black-backed vided valuable information: Kathy S. W. (Ted) Hoogendoorn, David Monk, Gull with orange legs. Dutch Birding, 3: 9. Adams, Anthony F. Amos, Robert L. An­ Fritz Mueller, Gunnel Rydström, and De­ De Schutter, G. 1989. L’identification des derson, Brad Andres, Ulf Antonsson, borah Sudran. Robert D. Barber, Paul Benham, Charles grands larides en Belgique. Aves, 25: 76–106. We thank Nina Root and her staff at W. Brasfield, Richard Bowen, R.J. Chan­ Farrand. J. Jr. 1983. The Audubon Society the American Museum of Natural History dler, John J. Christian, Clarence B. Master Guide to Birding. v.2. New York: Library, especially Debra B. Colchamiro, Diersing, Jr., Charles D. Duncan, Otto Alfred A. Knopf. Sarah F. Gramato, and Priscilla Watson, Frengen, James Granlund, Heinz Foxall, R.A. 1979. Presumed hybrids of the and staff at the New York Public Library, Haberyan, Daniel R. Heathcote, Robert Herring Gull and the Great Black-backed for their assistance. And, we thank Allison B. Janssen, Arnet Kvinnesland, the late Gull— a new problem of identification. Serge LaFrance, James E. Landing, Greg Andors, Helen Hays, and Mary LeCroy of American Birds, 33: 838. W. Lasley, Bruce Mactavish, Ian A. the Department of Ornithology at the Glutz von Blotzheim, U.N and K.M. McLaren, Joseph B. Milosevich, Arthur American Museum of Natural History for Bauer. eds. 1982. Handbuch der Vögel Morris, Bob O’Brien, Urban Olsson, Ken­ allowing us to examine specimens. Mitteleuropas. Band 8. Wiesbaden, Ger­ neth C. Parkes, Kevin D. Powers, Ronald We also thank Per Alström, Edward S. many: Akademische Verlagsgellschaft. J. Ryel, Noah Satat, Michel Savard, Ed Brinkley, Jon Dunn, W. (Ted) Hoogen­ Godfrey, W.E. 1986. The Birds of Canada. and Jean Schulenberg, Robert L. Scully, doorn, and Peter de Knijff for reviewing rev. ed. Ottawa: National Museums of John Shackford, the late Leonard A. Shel­ early drafts of the manuscript; and Paul Canada. ton, Hadoram Shirihai, Brian Taber, Lehman and Claudia Wilds for their editing, Grant, P.J. 1986. Gulls: A Guide to Identifi­ Roger Tidman, David Tomlinson, David which resulted in many improvements. cation. 2nd ed. Vermillion, South Dakota: Tipling, Jeffrey L. Walck, Claudia Wilds, Finally, the first author would like to Buteo Books. and Alan Wormington. Milton Heiberg thank Tomas Lundquist and Urban Grant, P., and K. Mullarney. 1989. The New kindly lent the resources of his studio and Olsson for their hospitality when he was Approach to Identification. Privately gave of his expertise in duplicating slides. in Sweden, and for showing him breeding printed. For answeringour requests for informa­ colonies of L. f. fuscus and L. f. inter­ Hansen, L. 1960. Krydsning mellem tion and/or photographs we thank Alien B. medius. The second author wishes to Sølvmåge (Larus argentatus Pont.) og Altman, Robert F. Andrle, J. Phillip Angle, thank Ted Hoogendoorn, Peter de Knijff, Sildemågc (Larus fuscus L.) fundet Paul J. Baicich, Stephen F. Bailey, Edvard K. and Norman van Swelm for their hospital­ ynglende sammen med en Sølvmåge. [Hy­ Barth, Gordon Berkey, Laurence C. Binford, ity when he was in the Netherlands. brid Herring Gull (Larus argentatus

380 BIRDING. OCTOBER 1995 Pont.) and Lesser Black-backed Gull (Larus fuscus L.) found breeding with a Herring Gull]. Dansk Ornitologisk Foren­ ings Tidsskrifter, 54: 85–87. Hario, M. 1986. Itämeren lokkilinnut määritys ja esiintyminen. [Larids in the Baltic Sea — identification and occur­ rence]. Helsinki: Lintutieto Oy. Harris, M.P., C. Morley and G.H. Green. 1978. Hybridization of Herring and Lesser Black-backed gulls in Brit­ ain. Bird Study, 25: 161–166. Harris, A., L. Tucker and K. Vinicombe. 1989. The Macmillan Field Guide to Bird Identification. London: The Macmillan Press. Harrison, P. 1983. Seabirds: An Identifica­ tion Guide. Boston: Houghton Mifflin. ———. 1985. Seabirds: An Identification Guide, rev. ed. London: Croom Helm. ———. 1987. A Field Guide to Seabirds of the World. Lexington, Massachu­ setts: The Stephen Greene Press. National Geographic Society. 1983. Field Guide to the Birds of North America. Washington, DC: National Geo­ graphic Society. ———. 1987. Field Guide to the Birds of North America. 2dn ed. Washington, DC: National Geographic Society. Olsen, K.M. 1992. Danmarks Fugle— en over­ sigt. [Birds of Denmark— a checklist]. Co­ penhagen: Dansk Ornithologisk Forenig. Urban, E.K., C.H. Fry and S. Keith, eds. 1986. The Birds of Africa. v.2. New York: Academic Press. van Kreuningen, J. 1980. Great Black- backed Gull Larus marinus with orange legs. Dutch Birding, 2: 14. Voous, K. H. 1962. Another presumed hy­ brid of Lesser Black-backed Gull and Herring Gull in the Netherlands. Ardea, 50: 171–172. Wilds, C. 1989. The terminology of plum­ age and molt. Birding, 21: 148–153. Wilds, C. and D. Czaplak. 1994. Yellow­ legged Gulls (Larus cachinnans) in North America. Wilson Bulletin, 106:344 –356. Yésou, P. 1991. The sympatric breeding of Larus fuscus, L. cachinnans and L. argen­ tatus in western France. Ibis, 133: 256–263.

FIELD IDENTIFICATION OF LESSER BLACK-BACKED GULL 381