WESTERN BIRDS

Volume 9, Number 4, 1978

LESSER BLACK-BACKED GULL IN CALIFORNIA, WITH NOTES ON FIELD IDENTIFICATION

LAURENCEC. BINFORD,California Academy of Sciences,Golden Gate Park, San Francisco, California 94118

On 14January1978 Ronald L. Branson,Benjamin D. Parmeter,John Parmeter and I saw a British LesserBlack-backed Gull (Larusfuscus graellsii)on the westside of Robert'sLake, Monterey, Monterey Co., California,about 0.8 km inlandfrom thePacific Ocean beach. This is the westernmostrecord for thespecies in NorthAmerica; the only previous western records are from Colorado, the Texas coastand the Northwest Territories (seeDiscussion). The onlyrace collected in North Americais L. f graellsii(American Ornithologists'Union 1957,Jehl 1958, Mumfordand Rowe 1963, Woolfendenand Schreiber1974), although the NorthwestTerritories bird and one observedat Newburyport,Massachusetts (Finch 1976) werethought to be nominatefuscus. SIGHTING Whendiscovered, the Montereybird was loafing with about80 other gullson a patchof bare ground near the lake edge and about 10 m from where we sat in our van. Included in the flock and thus available for directcomparison were adults of the CaliforniaGull (L. californicus), WesternGull (bothL. occidentaliswymani and L. o. occidentalis)and Glaucous-wingedGull (L. glaucescens), aswell as several American Coots (Fulicaamericana). We scrutinizedthe bird for 10minutes (1500-1510), using binoculars anda 20xspotting scope. Although clouds obscured the sun and a slight mist was falling,the fairly bright sky,open terrain and closerange affordedgood lighting. Branson obtained four good Kodachrome slides with the aid of a 400 mm lensset at f5.6, 1/60 sec.;analysis of the foot colorsof thevarious ages of CaliforniaGulls demonstrates that the color fidelityof the slidesis excellent. WesternBirds 9:141-150, 1978 141 LESSER BLACK-BACKED GULL

The LesserBlack-backed Gull spentseveral minutes preening but most of the time dozed with neck retractedand eyesoften partially closed,apparently much at ease.Eventually the arrivalof anothercar causedthe flockto rise and scatter,only a few birds returningto the loafingarea. The LesserBlack-backed flew inland,circled twice over a nearbypond and then flapped eastward alone until outof sight.When it took off, two of us (L.C.B.,B.D.P.) obtained views of the wing pattern. Despitean intensivesearch during subsequent weeks, the bird couldnot be found again.

DESCRIPTION Thefollowing description ofthe Monterey bird was written using only our original fieldnotes and microscopic examination ofthe four photographs (Figure 1). A copyof thispaper and the original photographs are on filewith the California Bird Records Committee.References to theHerring Gull pertain to the NorthAmerican subspe- cies,L. argentatussmithsonianus. Ageand molt: adult in freshbasic (winter) plumage; no wearnoticeable on wingor tail tips;when preening, bird twicespread left wing tip, revealingan outermost (10th) primary only about half-grown; slides indicate that the 9thprimary was not fully grown, its white apical spot merging in partwith that of the normallymuch shorter 8th; no other molt evident. Body size: length and bulk of body (includingwings and tail) slighdy larger than in CaliforniaGull, considerably smaller thanin WesternGull, and hencevery similar to thoseof smallHerring Gull. Body shape:perhaps slightly more elongatethan in Californiaand thusabout same as in Herring;head larger in proportionto body thanin mostindividuals of largergull species(e.g. Western Gull). Forehead: dove-shaped, slightly more vertical in relation to culmenthan in Californiaand very much less sloped than in Western.Bill sizeand shape:like thatof smallHerring or perhapsslighdy finer throughout;field observa- tions,supported by micrometermeasurements of slideimages, show bill wasabout 4 mm longerand 2 mm higherthan bills of nearbyCalifornias; upper and lower outlinesnearly parallel as in California,but culmen very slightly recurved in middleto producea veryslighdy bulbous tip; gonydealangle very weak; compared to adult Western'sbill, shorterand much shallower (hence also proportionately shallower), tip lessbulbous, and gonydealangle much less pronounced. Head streaks(do not show clearly in photographs):head white with narrow, sharplydefined, rather short, longitudinalstreaks of dark grayon crownand face,lengthening, widening and blurringon napeand hindneck;reminiscent of thoseof winteradult Ring-billed Gull (L. delawarensis)but lesssharp and numerous,and spotsof latter specieslacking. Underpartsand tail: solidsnow white, with no suggestionof darkeningthat would indicateimmaturity. Mantle: Dark Neutral Gray(capitalized colors from Ridgway 1912; seebeyond), paler .than jet blackof wing tips and about same"shade" (see beyond)as upper back (with daylight reflections) of nearbyAmerican Coots; a half- shadedarker than in nearbyadult L. o.wymani; a full shadedarker than in nearbyadult L o.ocddentalis; two shades darker than in adultCalifornias; no tingeof browncould be seen;scapulars broadly tipped with white. Primaries: above and below dark gray, distallyabove jet blackwith white apicalspots; outermost (10th) crossedby a subterminalwhite mirror (band) about as wide as long, well separated (by about width of mirror)from apicalwhite, embracing both webs,and slightlyindented both proximallyand distally along rachis; no whitetongues or mirrorsvisible on 9th or other primarieswhen tips spreadin preeningor flying,although we couldhave misseda smallwhite spoton the 9th; wing tips extendedwell beyondtail tip. Secondaries:above dark gray like mantle, with broad white tips; below (as seen in flight)gray, about as in adultWestern or perhapseven darker, with broad white tips; 142 LESSER BLACK-BACKED GULL winglinings white. Bill color:yellow with a brightred, orange-tinged gonydeal spot, nearScarlet-Red, confined to lowermandible, not reachingtip or tomium, and very large- abouttwice as long as high (shape unique in my experience)and thus nearly twicethe sizeof a Western's.Eye: iridesvery paleyellow with a few flecksof dusky accordingto our field notes,but nearlyg•ayish-white, tinged yellowish, in slides;in proportionto headsize, eye seemed about same size as California's and larger than Western's.Eyelid color: bright red, the exact shade somewhat obscured by shadowof browbut seemingin field and slidesslightly darker and lessorange than gonydeal spotand near Spectrum Red. Leg and foot color:tarsi and toesbuffy-yellow, not a pureyellow nor tinged with g•eenish or pinkish,close to Buff-Yellow;color unique in my experiencewith gulls;web colornot noted.Voice: noneheard.

IDENTIFICATION Similarityto L. fuscusgraellsii. The Montereybird was identicalto a typicalwinter adultL. f. graellsiiin all characteristics. Witherbyet al. ( 1941)state thatgraellsii ends its molt in Januarywith replacementof the Outer primaries,the conditionexhibited by the Montereybird. Judging from the fragmentaryliterature on thissubject, mostother large gulls terminate their basicmolt in fall,while molt in the Kelp Gull (L. dominicanus)is at its heightin Januaryand February. Ridgway(1912) presents a standardcolor scheme with whichmande colors,very. important to identification,can be com.pared. He pictures six shadesof graybetween white and black:Pallid Neutral Gray, Light NeutralGray, Neutral Gray, Deep Neutral Gray,Dark NeutralGray, and Dusky Neutral Gray. I term these"full shades."The colorshalfway betweenI term "half-shades,"which are easily seen both in thefield and hand when comparisonsare available.In the forms with which I am concernedherein, individualsvary no more than a quarter-shadeon eachside of the average,or a totalof one half-shade.All mantlecolors mentionedherein were determined from specimens,as many literature designations,even those using Ridgwaycolors, were found to be untrustworthy. In Figure1, the reader may compare the mantle of theMonterey bird, judged to be Dark Neutral Gray,with thoseof adult CaliforniaGulls (NeutralGray), a second-yearL.0. occidentalis(between Neutral Gray and DeepNeutral Gray; second-year birds are about a half-shadepaler than adults),and an American Coot (upper back Dark Neutral Gray but appearingdarker in slide).To testour visual judgment of mantlecolors, I took light meter readingsof museumstudy skins of variousspecies, includingthe CaliforniaGull, andcorrelated these with Ridgwaycolors. I thentook readings of the slideimages of Californiasand the Monterey LesserBlack-backed and calculateda "specimenvalue" for the latter. Thisfigure was the same as that for the coot'supper back (Dark Neutral Gray),a half-shadedarker than in L. o. wymani,and a half-shadepaler than in the Slaty-backedGull (L. schistisagus),thus closely matching our visualimpression. 143 LESSER BLACK-BACKED GULL

Witherby(1914) gives an excellentcolor plate of the headof an adult summergraellsii. Our bird matchedthis plate almostexactIv in bill proportions,gonydeal spot color, shape and extent, iris and eyelid colors,and eve-headproportions. In the Montereybird, however,the gonydealangle was slightly less pronounced (more like the third-winter bird pictured),and the grbundcolor of the bill wasmuch yellower, less orange; this latter differenceprobably is a reflection of the more advancedbreeding condition of the picturedbird. Barnes(1952), in discussingthe greatvariation in winter adult leg coloringraellsii, states that many immigrants to Englandin lateFebruary and Marchhave legs of"rich ochreyellow," a phrasethat except for the word "rich" would well describe the Monterev bird. Eliminationof similarJbrms.Despite the fact that the Monterevbird seemedidentical to L.f. graellsii,I deemedit necessarvto eliminateall other gulls of the world, becauseMonterey is well outside even the knownvagran%, range of that form. This requiredelimination on the subspecificlevel, as several races of HerringGull aresimilar to theLesser

Figure1. Adult British Lesser Black-backed Gull •Larusfuscusgraellsii; darkest-mantled bird,left center• at Monterev,California, 14 JanuaD' 1978. Also shown are a second- winter WesternGull (L. o. occidentalis;left foreground),American Coot (Fulica americana;and CaliforniaGulls (L. cali•rnicus;rem•iinder of gulls Photob)' Ronald L. Branson 144 LESSER BLACK-BACKED GULL

Black-backedGull. I made a thoroughsearch of the widelyscattered literature and examined specimensin the CaliforniaAcademy of Sciences,Museum of VertebrateZoology, Berkeley, and somefrom the National Museum of Natural History, Washington,D.C. Eugene Eisenmannkindly provided commentsbased on the collectionof the AmericanMuseum of Natural History,New York, and Jon Winter loanedphotographs of the Kelp Gull. This papertreats only those forms that arelikely to be confusedwith graellsiior aregrossly similar but mightbe unfamiliarto thereader. Table 1 liststhe charactersthat distinguishthe mostsimilar forms (those with mantlesdarker than Neutral Gray)from the Montereybird (and hence from graellsii).The lesssimilar forms are discussedbelow. Four similar species,the Kelp Gull, Great Black-backedGull (L. marinus),Slaty-backed Gull andWestern Gull, were easily eliminated by their charactersas listed in Table 1. Thayer'sGull (L. thayeri)differs markedlyfrom theMonterey bird in itsdark pink legs and feet, magenta eyelids,darker irides, much paler mantle (betweenPale and Light Neutral Gray),and white wing tips ventrally. The HolarcticHerring-Lesser Black-backed (argentatus-fuscus) group, which is much discussedbut poorly understood,caused the greatest difficulties.The prevalent school of•hought (e.g. Vaurie 1965) holds that there are only twoLesser Black-backed Gulls in the world,graellsii and nominatefuscus,while the remaining ten or soforms are subspecies ofL. argentatus.On the oppositeend of the spectrum,some authors (e.g. Voous1960) believe that thereare onlytwo Herring Gulls,smithsonianus andnominate argentatus, while all other forms are subspecies ofL. fu[cus. Someauthors (e.g. Stegmann 1934) consider the two species conspecific, eventhough they are sympatric over parts of theirranges. Dwight (1925) takes an intermediateposition, treating the "Yellow-leggedGull," cachinnans,asa separatespecies, vegae and thayeri as races ofL. argentatus, and taimyrensisand atlantisas subspeciesofL. fuscus;his monograph, however, loses considerable usefulness because it does not deal with all presentlyrecognized forms of the complex. For the purposeof identifyingthe Montereybird, I havetaken the mostconservative view, that of Vaurie (1965),who recognizestwo races of the LesserBlack-backed Gull, L.f. graellsii(Iceland, British Isles) andL. f. fuscus(Scandinavia, northwestern Russia), and ten subspeciesof the Herring Gull, divided into two groups.Included in the northern circumpolargroup of Herring Gulls, listedfrom westto east,are: a. argentatus(Iceland, British Isles, Scandinavia,northwestern Russia; includesargenteus and omissus);heuglini (northern Russia, northwestern Siberia;includes antelius); taimyrensis (north-central Siberia); vegae (north- easternSiberia; includes birulae); and smithsonianus (North America). The southerngroup, listed from westto east,includes the following:atlantis 145 LESSER BLACK-BACKED GULL

(Azores, Canaries);michahellis (Mediterranean); armenicus (Armenia); cachinnans(middle East,southwestern Siberia; includes barabensis and ponticus);and mongolicus(Mongolia, Manchuria). The aboveranges are veryincomplete; the readermay consultVaurie (1965) for details. Of the ten Herring Gull races,only argentatusand smithsonianus consistentlyhave pink legs and feet. In heuglini,atlantis, michahellis, cachinnansand armenicus,these parts are alwayssome shade of yellow, whiletaimyrensis, vegae and mongolicus may have either color (Vaurie 1965). The Herring Gull racessmithsonianus, argentatus, taimyrensis, vegae, michahellis,armenicus, cachinnans and mongolicus were easily eliminated by theirpale mantles, which range from Pallid Neutral Gray to NeutralGray and thusare at leasttwo shadespaler than that of the Montereybird. Additionaldistinguishing characters are as follows:smithsonianus and argentatushave orange eyelids and pink legs and feet; taimyrensis issaid to have orangeto orange-vermilioneyelids, little or no winter head streaking,and a largerbody; vegae is largerin bodybulk; michahellis is sedentaryand usuallyhas a slightlylarger mirror on the 10thprimary; armenicushas a verysmall population (and may not be a validrace) and is sedentary;cachinnans has the headstreaking absent or restrictedto the hindneckand completesits basicmolt in the fall; and mongolicusis considerablylarger in bodyand bill. The remainingtwo races of HerringGull, heuglini and atlantis, are the forms most similar to the LesserBlack-backed Gull, but nevertheless can be eliminatedwith certaintyon the basisof their palermantles and the other distinguishingcharacters listed in Table 1. Separationof graellsiifrom nominate fuscus is, of course,difficult in the field, but I believepossible in typicalbirds. In the latter race,the mantleis one shadedarker, nearly as dark as the primarytips (Witherby et al. 1941),and slightly tinged with brown to producea shadeof Fuscous ratherthan Neutral Gray. Also, in fuscusthe "Head andneck in winter [are]considerably less streaked" (Witherby et al. 1941).

DISCUSSION Everycharacteristic of the Montereybird perfectlymatches typical examplesofL. fuscus graellsii, and everyother gull form in the worldis eliminatedby two or more characters. Despite the unusual locality, our conclusionis supportedalso geographically,as none of the threemost similar forms (L. f. fuscus,L. a. heugliniandL. a. atlantis)has been definitely recorded in NorthAmerica, whereasgraellsii has. Furthermore, the LesserBlack-backed Gull seems to be undergoingrapid expansionin North America, althoughthe recentincrease in recordsmay be at leastin parta functionof improved awarenessand coverage on the part of observers.In recentyears, L. fuscus has been reportedmore frequentlyin Texas (Watsonand Goldman 146 LESSER BLACK-BACKED GULL

Table1. Characteristicsof selected adult winter gulls that distinguish them from the BritishLesser Black-backed Gull (Larusfuscus graellsii), including the one photo- graphedat Monterey, California on 14January1978. Key: N. -- Neutral;G. -- Gray;g. a• -- gonydealangle.

Lesser Black-backed Gull z• fuscusfuscus Head streaksfewer or absent; mande one shade darker andtinged brown (dusky Fuscous-Black [ --- Dusky N. G.]) and nearlyas darkas primarytips.

Herring Gull L argentatusheuglini Head streakson hindneckonly; mande one shade paler (DeepN. G.); basicmolt endsSep.-Oct. L a. atlantis Mantle 1•4shades paler (betweenN. G. and Deep N. G.); iris perhaps amber; eyelids perhaps orange; sedentary.

Kelp Gull L dominicanus Foreheadmore sloped;bill actuallyand proportion- atelyhigher; g. a. usuallymuch stronger; head streaks absentor on crown only; mantle two shadesdarker andtinged brown (very dusky Fuscous-Black [ -- nearly Black])and as dark as primarytips; gonydeal spot rounderand extendsto tomium and almostto tip; legs and feetvariable but usuallywith greenishtinge; basic molt at height(old feathersworn) in Jan.-Feb.

Great Black-backed Gull L marinus Bodymuch larger; forehead more sloped; bill actually muchlonger and higher and proportionately higher; g. a•much stronger; head streaks fewer or absent;mantle one shadedarker and tingedbrown (dusky Fuscous- Black[ ---Dusky N. G.]);mirror on 10thprimary merges or nearlymerges with white apical spot; mirror on 9th primary large;eyelid color somewhatmore orange; legsand feetpink; basic molt endsin fall;eye smaller relative to head.

Slaty-backedGull L schistisagus Bodymuch larger; bill actuallylonger and higher and proportionatelyhigher; g. a. stronger;mande one half- shadedarker (between Dark and Dusky N. G.);mirror on 10thprimary larger and nearlymerging with white apicalspot; usually large mirror on 9th primary;white tongueson 8th-6thprimaries; legs and feet pink to reddish;basic molt endsin fall; eyesmaller relative to head.

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Table 1 (cont)

Western Gull L occidentalis,all races Bodylarger; forehead more sloped;bill actuallylonger and much higher and proportionatelyhigher; g. a. much stronger;bill tip more bulbous;gonydeal spot smaller and rounder; basic molt ends in fall; eye smaller relative to head. L o. occidentalis Head streaksusually absent, or when present,wide and not sharp;mantle one shadepaler (Deep N. G.); iris darker, richer amber-yellow;eyelids rich orangish- yellow;legs and feet pink. L o. wymani Head streaksabsent; mantle one half-shadepaler (be- tweenDeep and Dark N. G.);iris darker, richer amber- yellow;eyelids rich orangish-yellow;legs and feet pink. L. o. livens Head streaksabsent; mantle one half-shadepaler (betweenDeep and Dark N. G.); iris clear,unflecked lemon yellow;eyelids lemon yellow.

1952; Webster 1970, 1977) and Florida (Woolfendenand Schreiber 1974; Stevenson1976); appeared once in Colorado(Denver, 11 Dec. 1976-1Jan. 1977;Webb and Conry 1978);and has becomeregular enoughin thenortheast (Buckley et al. 1977),middleAdantic coast (Scott 1977),and southernAdantic coast (Teulings 1976) that it no longer meritsgreat attention. Godfrey (1966) did not list the species for Canada, but it hassince been noted in the NorthwestTerritories (near Albert EdwardBay on VictoriaIsland, 17July 1972;Alsop and Jones 1973), Manitoba(5 June 1968; Rossand Cooke 1969),O•uebec (David and Gosselin1977), and Ontario(twice) and Nova Scotia(Alsop and Jones 1973). Currently,the LesserBlack-backed Gull is consideredprimarily a winter visitor in North America; it is not known to nest closer than Greenland.It may,however, be followingthe samehistorical pattern as theLittle Gull (L. minutus)and perhaps Black-headed Gull (L. ridibundus), both of whichinvaded eastern North America,slowly then rapidly increasedin number, establishedbreeding colonies, and are now appearingwith increasedregularity on the Pacificcoast (Winter and Manolis 1978).The LesserBlack-backed invaded in the 1930s,increased slowlyat first,then rapidly in the last10 years, and recently has occurred a fewtimes in summer.The Monterey bird maywell be a forerunnerof a Pacific coast invasion. The adultage suggests that our bird hadvisited Monterey in previous years, either as a transientor winter resident. Most winter residents, includingvagrants, occur first as juveniles and thenreturn to the same areain subsequentwinters. Such behavior inL. fuscus is demonstrated by 148 LESSER BLACK-BACKED GULL theTexas City Dike,Texas, bird thatappeared during three consecutive winters (Webster1970), and the Digby, Nova Scotia,bird that has winteredfor the last 8 years(Vickery 1977). The Monterey individual shouldbe soughtin futureyears, especially (in caseit is a transient)in mid-January. The unworn plumageand absenceof leg bandsargue against an escape,and I doubtthere are any captiveL. fuscus in NorthAmerica. The aspectof thebird givesno indicationof hybridorigin. The combination of bodyand bill size,mantle, leg, and eyelid color, and primarypattern rule out any geographicallyand/or biologicallyreasonable hybrid combination.That a hybrid would be identicalto graellsiiis alsovery unlikely. Identificationof adultdark-mantled gulls of theworld is difficult but notimpossible, given an exhaustivedescription made at closerange and preferablysupported by color transparencies;softpart colors, head shapeand bodybulk, not visiblein studyskins, are veryuseful. West coastobservers encountering an unknown dark-backed gull should note in extremedetail as many of the followingcharacteristics as possible: shadeof mantle comparedto all nearbyadult gulls, especiallythe WesternGull; shapesof headand bill, includingthe developmentof the gonydealangle and the overall height of thebill in relationto itslength; colorand shapeof the gonydealspot; color of the irides,legs, feet and especiallyeyelids; width, sharpness and distribution of headstreaks, and if possiblethe pattern of whiteon theouter primaries, especially the size and locationof mirrors and the extentof white or graytongues on the inner webs.

ACKNOWLEDGMENTS I thankNed K.Johnson for accessto thecollections of theMuseum of VertebrateZoology, Berkeley, Richard L. Zusifor carefullyselecting and loaning specimensfrom the National Museum of Natural History, Washington,D. C., andEugene Eisenmann for commentson specimens in the AmericanMuseum of Natural History, N.Y. RobertAndrews, Ronald L. Le Valley, Esther M. Serr, Bruce E. Webb and Glen E. Woolfendengenerously provided information on gulls,andJon Winter aidedin specimenresearch. Ronald L. Bransontook the photographs and, togetherwith BenjaminD. andJohn Parmeter,provided valuable expertiseand enjoyablecompanionship in the field.

LITERATURE CITED Alsop,F.J., III andE. T. Jones.1973. The LesserBlack-backed Gull in theCanadian Arctic. Can. Field-Nat. 87:61-62. AmericanOrnithologists' Union. 1957.Check-list of North Americanbirds. 5th ed. AOU, Baltimore, MD. 149 LESSER BLACK-BACKED GULL

Barnes,J.A. G. 1952.The statusof theLesser Black-backed Gull. Brit.Birds 45:3-17. Bucldey,P. A., R. O. Paxtonand D. A. Cutler. 1977.Hudson-Delaware region. Am. Birds 31:311-316. David, N. and M. Gosselin.1977. Quebecregion. Am. Birds31:310-311. Dwight,J. 1925.The gulls(Laridae) of theworld; their plumages, moults, variations, relationshipsand distribution.Bull. Am. Mus. Nat. Hist. 52:63-401. Finch, D. W. 1976. Northeasternmaritime region.Am. Birds30:690-695. Godfrey,W. E. 1966.The birdsof Canada.Natl. Mus.Canada Bull. 203, Biol.Ser. 73. Jehl,J. R., Jr. 1958.The LesserBlack-backed Gull in the New York City area.Auk 75:349-350. Mumford, R. E. and W. S. Rowe. 1963. The Lesser Black-backed Gull in Indiana. Wilson Bull. 75:93. Ridgway,R. 1912. Color standardsand color nomenclature.Publ. by the author, Washington,D. C. Ross, R. K. and F. Cooke. 1969. Lesser Black-backed Gull at Churchill, Manitoba. A new bird for Canada. Can. Field-Nat. 83:399. Scott,F. R. 1977.Middle Adanticcoast region. Am. Birds31:316-319. Stegmann,B. 1934. Ueber die Formen der grossenMo•ken ("subgenus Larus") und ihre gegenseitigenBeziehungen. J. Ornithol. 82:340-380. Stevenson,H. M. 1976. Floridaregion. Am. Birds30:708-711. Teulings,R. P. 1976. SouthernAdantic coast region. Am. Birds30:51-54. Vaurie, C. 1965. The birds of the Palearctic fauna, non-Passeriformes.H. F. and G. Witherby, Ltd., London. Vickery,P. D. 1977.Northeastern maritime region. Am. Birds31:304-309. Voous,K. H. 1960.Atlas of Europeanbirds. T. Nelsonand Sons,Ltd., Amsterdam. Watson,F. G. and L. C. Goldman. 1952. SouthTexas region. Audubon Field Notes 6:254-257. Webb, B. E. andJ. A. Conry.1978. First record of a LesserBlack-backed Gull in Colorado. West. Birds 9: 171-173. Webster,F. S.,Jr. 1970.South Texas region. Audubon Field Notes24:518-521. Webster,F. S.,Jr. 1977.South Texas region. Am. Birds31:349-351. Winter,J. and T. Manolis.1978. Middle Pacificcoast region. Am. Birds32:394-397. Witherby,H. F. 1914.A studentof gulls.Brit. Birds7:306-312, color Plate 18. Witherby,H. F., F. C. R. Jourdain,N. F. Ticehurstand B. W. Tucker. 1941.The handbookof Britishbirds, Vol. 5. H. F. and G. Witherby,Ltd., London. Woolfenden, G. E. and R. W. Schreiber. 1974. Lesser Black-backed Gull in Florida. Florida Field Nat. 2:20-21.

Accepted7 December 1978

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