Range Expansion of the Glaucous-Winged Gull Into Interior United States and Canada

WESTERN BIRDS

Volume 26, Number 4, 1995

RANGE EXPANSION OF THE GLAUCOUS-WINGED GULL INTO INTERIOR UNITED STATES AND CANADA

LAURENCE C. BINFORD, HCR-01, Box 164, EagleHarbor, Michigan49950 DAVID B. JOHNSON, 504 Crown Point Drive, Buffalo Grove, Illinois 60089

Historically, the Glaucous-wingedGull (Larus glaucescens)has been consideredan almoststrictly coastal species in North America, only occa- sionallystraying very far inland. It breedsalong the Pacificcoast and on nearbyinland lakes from Alaskasouth to northwesternOregon and winters from the Bering Sea south to southernBaja Californiaand the Gulf of California (A.O.U. 1983, Verbeek 1993). In the most recent monograph on the species,Verbeek (1993) consideredthis speciesregular in small numbersin Sonora, casualin winter in easternWashington, Idaho, Mon- tana, Utah, Arizona, New Mexico, and centralCalifornia, casualin migration in Alberta, and accidentalin Yukon, Manitoba, and Oklahoma. Verbeek(1993) gaveno informationon historicalchanges in distribution. Muchearlier, however, the specieshad beenshown to havespread in winter from the coast inland along the Columbia River system into eastern Washington(LaFave 1965) and adjacentOregon [e.g., American Birds (AB) 29:91, 1974]. Fischer (1988) and Tove and Fischer (1988) believed that recordsfor Utah in the mid 1980s representedthe beginningof expansionof the winter range into the easternGreat Basin. Here we extendthe studyof the Glaucous-wingedGull's inland expansion to all interior western statesand provinces(except Yukon) and, lesscom- pletely, to inland portionsof Pacificcoastal states and provinces(except Alaska).Our data considerablymodify the species'status in some of the regionslisted by Verbeek(1993) and add Saskatchewan,eastern Oregon, Nevada, southeasternCalifornia, Colorado, and Illinoisto his range. We presentevidence for a recent, ongoing,potentially widespread and permanent rangeexpansion into the interiorof westernNorth America.We also discussfactors that may accountfor this spread and compare them to dispersaltheory. WesternBirds 26:169-188, 1995 169 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

METHODS

We thoroughlysearched Audubon Field Notes, American Birds, and National Audubon Society Field Notes from 1950 through 1993. We contactedlocal authorities(see Acknowledgments for names)and records committeesin all statesand provinceswest of the MississippiRiver and some to the east, as well as museumsknown to house inland Glaucous- wingedGull specimens. We reviewedstate and provincialmonographs, but reliedon our contactsto providelocal publications not otherwiseavailable to us.

INLAND EXPANSION

In the followingdiscussion, each individualis consideredone "record"; see the Appendix for details and citations. The terms "vagrancy"and "vagrant"are usedloosely for individualsoccurring inland from thisspecies' "normal"Pacific coast range. Interior Records

We have accumulated97 records for interior states and provinces, distributedas follows:Nevada (28, two of which were seen alsoin Arizona), Idaho (23), Utah (14), Alberta (14), Arizona (5, includingtwo seen also in Nevada), Colorado (5), Montana (4), New Mexico (2), Saskatchewan(1), Manitoba(1), Oklahoma(1), and Illinois(1). Althoughsome of theserecords may representmisidentifications (see caveat in Appendix), nine are sup- portedby specimens,at least 19 by photos,and eight by archivedwritten descriptionsaccepted by recordscommittees, so the species'occurrence inland is well documented.We also have many recordsfrom inland loca- tions in coastalstates and provinces;these are too numerousto list in the Appendix, but some are cited in the text. Accordingto local authorities,the specieshas not been reported in Arkansas, Iowa, Kansas, Louisiana,Minnesota, Missouri, Nebraska, New York, Ontario, South Dakota, Texas, or Wyoming. Documentationsfor Michigan and North Dakota records have not been acceptedby state records committees.

History of Winter Expansion The earliest record for interior states and provinceswas in 1912 at Capron, Oklahoma. Thus vagrancy is not entirely recent. No further recordswere forthcominguntil the mid 1950s, with singlebirds collected alongthe ColoradoRiver in Arizona in 1954 and 1956. [Additionalreports from Coloradoin 1956 (twosightings), Montana in 1955, andNew Mexico in 1954 and 1955 were duringthis same early period;although these are not acceptedby us or by regional authorities,neither have they been formallyrejected by recordscommittees.] This early period of vagrancy continuedslowly, with sightingsat Bear Lake, Alberta,in 1958 and 1959, near St. Paul, Alberta, in 1960, at Coeur d'Alene, Idaho, in 1963 and 1965, at Churchill,Manitoba, in 1964 (June),and at Valleyview,Alberta, in

170 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

1966, bringingto 10 the numberof individualsaccepted for inlandstates and provincesprior to 1971. Significantly,the Glaucous-wingedGull beganto invadeeastern Wash- ingtonduring the sameearly period,occurring first in the PotholesReser- voir region on 22 April and 4 May 1954 (adults;Weber 1981), the same year as in Arizona,and then at Spokanefrom 5 to 28 February1956 Ithree birdsphotographed; Audubon Field Notes (AFN) 10:268; LaFave 1965], on 9 February 1957 (AFN 11:282; LaFave 1965), on 16 February1961 (two immatures:AFN 15:346: LaFave 1965), and on 27 January 1962 (AFN 16:351 ). Meanwhile, the speciesbegan to be seen along the ColumbiaRiver in southeasternWashington (e.g., an adult at O'Sullivan Dam, 16 January 1959: LaFave 1965 ). About 1971 vagrancyseems to havebegun slowly escalating (Figure 1). Nevadarecorded its first Glaucous-wingedGulls in 1971, and one to four were seen each winter through 1977-78• Thereaftercame a near hiatus (onlysix birds), probably due to poor coverageor non-reporting.Beginning in 1991-92, however,from one to threehave been recorded annually. In Idaho, after the two initial sightingsin 1963 and 1965, the specieswas

Winter Season(years)

Figure1. Annualdistribution of individualGlaucous-winged Gulls (n -- 93) in interior statesand provinces during winters 1952-53 to 1993-94. FiveJune-August records were placedin the previouswinten 171 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

recordedonly five times until 1986-87. Since then it has been of nearly annualoccurrence, with five individualsin 1993-94. In Alberta, where this gull is only a transient,escalation seems to havestarted in the early 1980s. As would be expectedin an expandingspecies, areas farther from the Pacificcoast had their firstsin later years:Colorado, 1981; Utah, 1983; Montana, 1985; New Mexico, 1990; Saskatchewan,1991; Illinois, 1992. Fischer(1988) suggestedthat the nine birds recordedin the winters of 1984-85 and 1985-86 aroundGreat Salt Lake, Utah, represented"a real changein status"and "the beginningof expansionof the winter rangeinto the easternGreat Basin." The firstrecords for southeasternOregon, where habitat and observersare scarce,were at Farewell Bend, Malheur Co., 16 November1987 and at MalheurNational Wildlife Refuge, 19 December 1988 (Gilliganet al. 1994 ). Far to the south,small numbers have occurred with some regularityat PuertoPefiasco, Sonora, sinceabout 1982, when sevenwere seen on 12 February(AB 36:319; S.M. Russellin litt.) Meanwhile,in easternWashington and adjacentOregon, the specieshad becomea regularwinter visitorby the winter of 1974-75 (AB 27:797, 29:718; Weber 1981), aboutthe sametime it reappearedin Idaho after a nine-year absence.For example, 10 were at Umatitla, Oregon, on 23 November1974 (AB 29:91). This patternhas continued, for exampl.e,with eight birds at Pasco, Washington, and two at nearby Richland on 4 December 1985 (AB 40:305), until today the speciesnot only receives relativelylittle noticein winterbut hasbeen termed "common"along some sectionsof the ColumbiaRiver in easternOregon (Gilligan et al. 1994 ). The Glaucous-wingedGull appears to be on the increasealso in far inland California.The first recordwe can find for the Central Valley was of an immature at Sacramento 9-20 December 1969 (AB 24:535). Thereafter the specieswas rarely reported until fall 1985, when 14 were found (AB 40:330). At least 11 were presentin the winter of 1986-87 (AB 41:224) and eight in 1987-88 (AB 42:316), bringingthe total to at least51 in 19 years(AB). It now occursannually in suchnumbers that it no longerreceives notice in American Birds/National Audubon Society Field Notes (NASFN). This speciesseems to be increasingalso at its only other regular far-inlandCalifornia locality, the SaltonSea, wherea minimumof 74 birds havebeen found, mostly in late winterand spring,and it hasbeen reported duringall but three yearssince spring 1965 (AB; Garrettand Dunn 1981). We doubtthat coverageof the SaltonSea hasimproved much in the last30 years,yet after 18 winterswhen no more than threewere seenin one year, 10 appearedin 1982-83 as the resultof a fish die-off(AB 37:338), five in 1989-90 (AB 44:329), and 10 in 1993-94 (NASFN 48:248). Elsewhere in the far interiorof the state,we note the followingSiskiyou Co. localities and years of occurrence(AB): Tule Lake (1977, 1991), Lower Klamath National Wildlife Refuge (1983), and Yreka (1989). There are also four recordsfrom the California side of Lake Tahoe (9 January 1962, AFN 16:361; 20 December 1972, AB 26:651; 17 January 1975, AB 29:727; and 26 November1975, AB 30:121) and one from BridgeportReservoir, Mono Co. (20 June 1987, AB 42:1337), a Great Basinoutpost only about 37 milesfrom a Nevadarecord at Walker Lake. Althoughthese California data may, as suggestedfor the CentralValley, "reflectobserver effort" (AB 172 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

41:324), we suggestthat the apparentincrease is part of the largerpattern discussedin this paper. Figure1 depictsthe annualincrease in numberof recordsfrom interior statesand provinces.Possibly the currentspread was initiated in the 1950s, or even earlier.However, that the populationremained stable at a very low levelfor at least18 yearsthrough winter 1970-71 suggeststhat the sudden (thoughsmall) increasein 1971-72 is a more accuratestarting point. Concomitantly,the early 1970s sawan escalationalso in the CentralValley of California and in easternWashington and Oregon. The peak in winter 1984-85 is due to a specialstudy of rare gullsin Utah (Fischer1988, Tove and Fischer1988) and hencemay not be significantin regardto the timing of escalation.If we disregardthese particularUtah records,the strong upwardtrend starting just after a low in 1987-88 appearsmore significant. Fromdata in Figure1 we calculatethat the averagenumber of recordsper yearfor the wintersof 1953-54 through1970-71 (18 years)was 0.5; for 1971-72 through 1983-84 (13 years), 2.23; and 1984-85 through 1993-94 (10 years),5.5. Ten-yearaverages yield similar results.

Inland Breeding The Glaucous-wingedGull has also extended its breeding range inland, to islandsin the ColumbiaRiver of easternWashington and Oregon.At Miller Rocks,Sherman Co., Oregon,four pairswere seenin 1974, adultseach year throughat least1987, and adultsnearby through 1994. Chickswere foundin 1977, and three nests,with one, two, and three eggs,in 1978. At LittleMemaloose Island, near The Dalles,Oregon, three pairswere seenin 1974, adultsin 1978, and a nestwith three eggsin 1981. Also in 1981, a nestwith three eggswas noted on Island20 at Richland,Washington, 548 kilometersupstream from the mouth,and adultswere seenin a gullcolony on Three-mile Island.These data, summarizedfrom Gilliganet al. (1994) and Conoverand Thompson(1984), demonstratelittle increase in population numberssince 1974 but do show a rather rapid spreadupstream. In addition,hybrids between Glaucous-winged and Western(L. occidentalis) gullsnested on Island18 in the ColumbiaRiver at Richland,Washington, in 1981 (Weberand Fitzner 1986). Even the extralimitalnesting of a Glau- cous-wingedGull mated to a Western Gull on the coast at Pt. Reyes, California,in summer1994 (NASFN 48:985) couldbe relatedto the same factorscausing inland expansion. Age Composition Of the 77 individualsfrom interiorstates and provincesfor which we have detailedage data, 54 (70.1%) were first-year(first-winter or first- summer)birds, 13 (16.9%) second-year,two (2.6%) third-year,and eight (10.4%) adult.An additionalsix were statedto be "immatures."The high percentageof first-yearbirds may reflecta combinationof normal age distributionplus a possiblepropensity for thisage to dispersefarthen The lowernumber of second-yearbirds and near absenceof third-yearindividu- alsrepresent a typicalage composition in four-yeargulls. What is unusualis the low countof adults,which on the coastin winternormally far outnum~

173 RANGE EXPANSION OF GLAUCOUS-WINGED GULL ber second-yearbirds and slightlyexceed or approximatethe numberof first-yearbirds (Verbeek 1993). Thus the interior sampledoes not have a normalage structureand thereforecannot represent a stableself-perpetuat- ing population.The presenceof adults,on the other hand, impliesthat the inlandenvironment is not a total populationsink that eliminatesthe birds beforethey have a chanceto breed.

ROUTE OF DISPERSAL

Weber (1981) suggestedthat Glaucous-wingedGulls reaching northern Idahocame through eastern Washington and Oregonvia the Columbiaand Spokane rivers, and as the species'pattern of initial occurrenceand subsequentexpansion in all three statesis similar,we agree. How this gull reachedother regionsof the interior, however,is much more problematical.Possibly, birds in southernIdaho and perhapsfarther southin Utah and Nevada, even Arizona, originatedin easternWashington and Oregon and northern Idaho. Once they passedthe Cascades,via the ColumbiaRiver, birdsmight have a clear passagesouthward through the Great Basin.Although we cannotrefute this hypothesis,we note that there are no recordsfor the area of Lewiston,Idaho, situatedat the confluenceof the Snake and Clearwater rivers (Weber 1981). while there are records farther southin the Boise-Namparegion. Furthermore, the Great Basinis fraughtwith 8-10,000-foot mountainranges that seem hardlyless daunt- ing than the Cascadesand Sierra Nevada. Instead, we suggestthat birds pass inland directly over (or through a number of passesin) the Cascadesand Sierra. As evidencefor this idea standthe four California records(mentioned above) and one Nevada record for Lake Tahoe, at 6229 feet elevation on the California-Nevada border. That the Glaucous-wingedGull is capableof suchover-mountain flights is evidencedby the 26 recordseast of the Rocky Mountainsin Alberta, Saskatchewan,Montana, Colorado, Oklahoma, and Illinois. Glaucous-wingedGulls could enter the Central Valley of California via San FranciscoBay and the Sacramento delta. However, to reach such localitiesas Redding(AB 39:98) in the northern SacramentoValley, or Yreka farther to the north, they would have to retreat a considerable distancenorthward. We think it more likelythat they simplyfly overthe low Coast Ranges. All 19 Albertaand Coloradorecords are from east of the RockyMoun- tains, and all but one (Colorado,summer) are of springor fall transients. Geographysuggests that birdsmay use the leadingline of the range to fly southeastwardfrom Albertathrough Montana, Colorado, and Oklahomato an unknown wintering destination,perhaps the Gulf coast, where we predictthe specieswill eventuallybe discovered;this path wouldalso take birdsthrough Wyoming, which has no recordsyet. The Glaucous-wingedGull probablyuses the Salton Sea as a stepping stonebetween the Pacificand the Gulf of California,as suspectedfor other aquaticbirds (Garrett and Dunn 1981:30). The recent concentrationsat thissea may consist of birdsthat were headingto or from the Gulfbut were

174 RANGE EXPANSION OF GLAUCOUS-WINGED GULL attractedto ephemeralfood resources like the fishdie-off in 1982-83 (AB 37:338). Thusthe species'abundance at the SaltonSea may be intimately relatedto the numberof birdswintering or intendingto winteron theGulf.

CURRENT STATUS

Here we summarizethe current inland statusof the Glaucous-winged Gull, first geographicallyfor all inlandregions, and secondtemporally for onlyinterior states and provinces.See the Appendixfor details.We usethe followingscale of abundanceand regularity:for annualoccurrence, common (an average of 1-10 per day may be found), uncommon (3 per month-1 per day), or rare (1 per season-3 per month); for nonannual occurrence,occasional (1 individualevery 1-3 years),casual (1 per 3-11 years),or accidental(1 per 11+ years).For mode of occurrence,we use visitant for birdsseemingly remaining only short periodswithin winter or summer;resident for birdsremaining most or all of one winteror summer; and transientfor what appearto be springor fall migrantspassing through a region.We haveavoided the term vagrantbecause we contendthat today many interiorbirds are within their newlyestablished "normal" range. The numberof individualbirds recorded is givenin parenthesesafter the name of the area. Extremedates given for variousperiods are basedon our data and undoubtedlywill be expandedby futurerecords. Geographical All•erta (14); occasionalspring (21 March-9 May) and casualfall (mid September-14 November)transient; we treat two records, 11 and 6-21 August,as representingcasual summer visitants, as they are earlierthan the speciesis supposedto migrate(Verbeek 1993) and earlierthan any coastal California arrivaldates we can find. Arizona (5): casualwinter resident(12 December-24 February)and accidentallate-fall transient (two, 30 October and 17 November). Briti$1• Colt•rnl•ia, eastern (many): spring and fall transient, casual in north, occasionalor rare in south. California interior (many):as a winter visitantand resident,rare at the Salton Sea and in the Central Valley, casualto accidentalelsewhere in the far interior, and commoner near the coast; as a summer residentand visitant, casualat the Salton Sea and casual to accidentalelsewhere (but no Central Valley record).Colorado (5): casualspring transient(1 March-1 May) and accidentalsummer visitant (one, 24-25 July).Idaho (23): in north, occasional (probablyrare) during fall and winter (30 October-8 March),most individuals being late-falltransients or seeminglywinter visitants,with only two knownto be winter residents(18 November-8 February);in south,accidental fall transient(one, 26 October)and midwintervisitant (two, 4 January, 17 February).Illinois (1): accidentallate-fall transient (27 November-12 December).l¾1anitol•a (1): accidentalsummer visitant or resident(collected 1 June).l¾1ontana (4): accidentalspring transient (one, 21 March-6 April), late-falltransient (one, early November),winter visitant(one, 26 January), and winterresident (one, 7 December-18 April). l•levada (28): rare during fall and winter (21 October-27 February),with individualsclassed as 175 RANGE EXPANSION OF GLAUCOUS-WINGED GULL occasionallate-fall transients (21 October-earlyJanuary, main migration period from mid Novemberto mid December),casual midwinter visitants, and occasionalwinter residents(7 December-21 February);accidental springtransient (two, 27 March and 3 May). "One or two individualsalmost everywinter" (C. C. Lawsonin Alcorn 1988 ); "regularin smallnumbers from Novemberthrough February" (L. A. Neel in litt. 1994). New l•!exico (2): accidentalwinter resident (21 January-7 March) and nonbreeding summer resident (bird discovered12 February remained through next summer into October, when collected).Oklahon•a (1): accidentalwinter visitantor resident(collected 15 February).Oregon, eastern(many): winter resident,uncommon [Gilligan et al. (1994) say '•common"]along Columbia River at least as far inland as Umatilla and casualelsewhere; occasional or casualbreeding permanent or summerresident along this river as far inland as Miller Rocks, Sherman Co. Saskatchewan (1): accidental late-fall transient(9-16 November).Sonora (14 reports,some of severalindividu- als):winter resident,occasional (probably rare) at Puerto Peaasco, casual south to the Guaymasarea (S.M. Russellin litt.). Utah (14): occasional (probablyrare) during fall and winter (10 November-26 February),with individualsclassed as casual late-fall transients(10 November-28 Decem- ber) and midwintervisitants and accidentalwinter residents(one, 7 Decem- ber-26 February);accidental spring transient (two, 26 Febraury-13 March, and 30-31 March). "It appearsnow to be a regularmigrant and winter visitant"(Fischer 1988). The paucityof recordsin recentyears is because: "no one has looked; I suspectthe Glaucous-wingedis a regular but rare winter visitor"(E. Sorensenin litt. 1994). Washington, eastern(many): winter residentalong the Columbiaand Spokanerivers, uncommon as far as Richlandand occasionalfrom thereto Spokane;breeding permanent or summer resident, at least casual, along the Columbia River east to the Richland area.

Temporal Here we discussseasonal distribution in interior statesand provinces,as shownin part (excludingsummer) in Figure 2. Fall. Fall migration beginsas early as mid September(not shown in Figure2) in Alberta,and elsewhereaccelerates sharply in the lastfew days of October.The earliestarrivals in Saskatchewan,Montana, Idaho, Nevada, Utah, and Arizona all fall between 21 October and 10 November. Of the nine known winter residents, seven arrived between 30 October and 12 December,with five of these on either 7 or 12 December.Migration increasessteadily to a peak in mid December,although some individuals continueto arrivethrough late Decemberand apparentlyeven early Janu- ary (Nevada). Winter.Taken as a whole,the populationremains rather stable from mid December through mid February,although in at least Idaho, Montana, Utah, and Nevada a few birdscontinue to wander, i.e., appear, staybriefly, and leave, even in midwinter(about 10 January-10 February).Most winter residentsand visitantsdisappear during the last two weeks of February, when a fairly steadydecline in numbersbegins and continuesthrough mid 176 RANGE EXPANSION OF GLAUCOUS-WINGEDGULL

'• 14 '• 12 • 10

2 0 Sep Oct Nov Dec Jan Feb Mar Apr May

Figure 2. Seasonaldistribution of individualGlaucous-winged Gulls (n -- 86) in interiorstates and provincesduring approximately5•ay periods,September-May, 1912-1994. Each individualis shown for every period it was present.

March. Overwinteringhas been recorded for Montana, northern Idaho, Nevada (both northern and southern), Utah, Arizona, and New Mexico. Montana has the MissouriRiver, and the other five states have large reservoirs,lakes, or rivers that remain open through the winter and are capableof supportinggulls. In Albertaand Saskatchewanthe speciesis only a springand/or falltransient; the absenceof largerivers and the freezingof stillwaters preclude winter occurrence.Overwintering in northernIdaho is probablymore commonthan the two recordssuggest; observers there as elsewhere should record inclusive dates of individual birds to determine the extent of overwintering. Spring. The slightpeak in late March and early April reflectsspring transientsin Albertaand Coloradoand, to a lesserdegree, Nevada, Utah, and Montana.Dates for springstragglers extend to 18 April in Montana, 1 May in Colorado,3 May in Nevada,and 9 May in Alberta. The entire pattern detailedabove is very similar to that on the South FarallonIslands off centralCalifornia (DeSante and Ainley 1980). Thusthe interior population, although consistingof '•vagrants"in the sense that individualsare outsidethe species'normal coastalrange, exhibitsa pattern typicalof a winter resident;there are no temporalanomalies that might indicatea vagrantstatus. Summer. Six individualshave been foundin interiorstates and provinces during summer, single birds in Manitoba, Colorado, Nevada, and New Mexico,and two in Alberta.However, the birdfound in Nevadain Julywas discoveredas a disarticulatedskeleton and hencearrived much earlier. Only the one in New Mexicois knownto haveoversummered, although the one in Manitobamight have if it had not beencollected on 1 June. Hence, some individualsoccur in summer in the interior, but most, even immatures, apparentlyreturn to the coastor expire.

177 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

CAUSES OF INLAND EXPANSION

Coverage When a speciesundergoes a veryrapid expansion, as in the casesof the House Finch (Carpodacusmexicanus; Mundinger and Hope 1982) and CattleEgret (Bubulcus ibis; Crosby1972), the changeis quicklydetected and confidentlyattributed to naturalcauses. A slowdispersal, however, like that of the Glaucous-wingedGull, evenwhen documented,is often passed off as an artifactof improvedcoverage by observers.We do not denythe importanceof better coverage.The proliferationof birders,better commu- nication among them, improvedoptics, identificationguides, and tech- niques,and the greateremphasis on findingrarities clearly have contributed to an increasein recordsof vagrantsof many species,including the Glaucous-wingedGull. Nevertheless,for severalreasons we believe that increasedcoverage alone cannot accountfor the apparent inland expansion of this species. The possibilitythat past observersoverlooked the Glaucous-wingedis unlikely.The only similarspecies then seen regularlywith which it might have been confusedwas the Herring Gull (L. argentatus), which was uncommonenough throughout much of the westerninterior that all were scrutinized. During the 1950s and 1960s, inland records of the then common California(L. californicus),Ring-billed (L. delawarensis),and Franklin's(L. pipixcan) gulls,the scarceHerring Gull, and the rare Bonaparte'sGull (L. philadelphia)were studiouslyreported and publishedin Audubon Field Notes. Reports came from some of the same localitieswhere Glaucous- wingedGulls have been found more recently, such as Spokane, Washington (birded in the early 1960s), FarmingtonBay, Utah (1963), Ft. Peck, Montana(1964), Coeur d'Alene, Idaho (1966), and Calgary,Alberta (early 1970s). Clearly then, birderswere paying attentionto gullsand at the properlocalities. Yet they identifiedno Glaucous-wingedGulls. Neitherdid they find severalother species,most of them easilyidentified, suchas Sabine's(Xerna sabini), Glaucous(L. hyperboreus),and Western gulls, the Black-legged Kittiwake (Rissa tridactyla), and jaegers (Ste rco ra ri us spp.). Today,however, most of theseoccur somewhere in the western interior virtually every year, often with multiple sightings.For example, for Nebraska,Kansas, Oklahoma, and northern Texas, F. Will- iams (AB 33:192, 1979) wrote, "In the past ten years the status of Bonaparte'sGull has changedfrom 'rare transient'to 'commonmigrant and winter resident'"and "It appearsthat Sabine'sGulls may be following the samepattern, as they are now reportedsomewhere in the Regioneach fall or winterseason." The laststatement has also been appliedto the Black- legged Kittiwake (AB 31:195, 1977). In fall 1981, birders found 13 Sabine'sGulls in Utah, Nevada,Wyoming, and Colorado(AB 36:202). In fall 1990 the same stateshosted all three jaeger species,Heermann•s (L. heermanni), Mew (L. canus), LesserBlack-backed (L. fuscus),Western, and Glaucous-wingedgulls, Black-leggedKittiwake, and "only•' eight Sabine'sGulls (AB 45:133), whileNorth Dakotahad 11 speciesof gulls(AB

178 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

45:121). Many other examplesfrom throughoutthe westerninterior could be cited. Clear]y, then, the number of recordsfor many gulls,in additionto the Glaucous-winged,has greatly increasedin recent years. We contendthat the magnitudeof thisincrease is too greatto be accountedfor by coverage alone and that severalnew factorshave recentlycombined to increasethe actual number of birds and improvetheir detectability.

Mechanismof Dispersal Before discussingthese new factors, we present a summary of the mechanismsof dispersal as we believethey might apply to the Glaucous- wingedGull, basedlargely on Udvardy(1969, especiallypp. 71-75). Vagrancy (nomadism),enhanced by the innate urge and ability to migrate, may be of two major types, slow penetrationinto areas adjacentto the normal range and jump-dispersal,over inhospitableterrain, into more distant,sometimes far-flung regions. In eithercase the pioneersencounter newly availablesuitable habitat. Both typesof movementare repeated,in varyingdegrees of regularityand abundance,but potentiallyannually in smallnumbers, resulting in recruitment,fostered by philopatryand longevity. The foundersestablish local nuclear populations, first in winterand then in summer;breeding may ensue.The neareran area to the corepopulation, the more often vagrantsreach it and the more rapidlya new populationis established there.

BreedingPopulation One important change leadingto inland expansionis the population explosionin large North Americangulls (e.g., Conover 1983), includingthe Glaucous-winged.According to Verbeek (1993), a population on four islandsin the westernAleutians nearly doubled from 1970 to 1979; one in the Straitof Georgia,British Columbia, expanded from 6150 pairsin 1959 and 1960 to 13,002 in 1986; in BritishColumbia as a whole, populations have increased350% in the last 50 years.The large colonyon Protection Island,Washington, grew from 4300 pairs in 1976 to 6785 in 1984, a mean annual increaseof 5.9% (Reid 1988, Verbeek 1993). Such increaseshave been attributedto protectionfrom human persecu- tion (takingof eggs, adults,and young for food, sport, and the millinery trade),better food resources(garbage dumps, farms, domestic sewage, fish waste), and more breeding sites afforded by islandsin new reservoirs (Conover1983, Reid 1988). Mostof thesefactors also favor gulls in winter. An increasein the core breeding population of a speciesmay cause intraspecificpopulation pressures, such as overcrowding,that trigger an intrinsicrestlessness, leading to nomadismin some individuals(Udvardy 1969). In addition,most if not all migrant speciesgenerate vagrants to a greateror lesserdegree. If at leastsome vagrants are misorientedmigrants (DeSante1973), a growingbreeding population should cast off increasing numbersof vagrants.A third possibilityis the evolutionof a new genotype favoringvagrancy; this is more likely "in marginal,vulnerab]e areas and bridgeheadsof expansion"(Udvardy 1969). The new breedingpopulation 179 RANGE EXPANSION OF GLAUCOUS-WINGED GULL in easternWashington and Oregon, althoughstill very small,seems to qualify,having colonized an environmentdissimilar to that on the coastin its movingfresh water, freshwater prey, and inlandclimate.

Habitat

The inland environmentencountered by recent vagrantshas changed graduallybut significantly.It now includesmany large garbage dumps, reservoirs,and hydroelectricdams, habitats that at leastin combinationcan supportlarge gulls. Of the 86 individualGlaucous-winged Gulls for whichwe have habitat data from interiorstates and provinces,32 (37.2%) were found on reservoirs, 27 (31.4%) at dumps, 14 (16.3%) on rivers, 8 (9.3%) on natural lakes,two (2.3%) on dumpsand adjacentrivers, one (1.2%) on a riverand a lake, one (1.2%) at sewageponds, and one (1.2%) inland. With the proliferationand risingaffluence of humanity,edible waste has increaseddramatically, and garbagedumps have becomelarger and more numerous.These are veryattractive to the Glaucous-wingedGull, as the 29 (33.7%) birdsfound in this habitatdemonstrate. However, the importance of this habitatshould not be overestimated,as 57 (66.3%) birdswere seen onlyin otherhabitats. Even along the Pacificcoast, many Glaucous-winged Gullsfeed in naturalenvironments (pers. obs.), and in the interior,use of dumpsis confinedlargely to Utah and Idaho.On the otherhand, our data probablydo not treat the subjectfairly, because other birds,especially in Idaho,although recorded on riversor lakes,very likely fed at nearbydumps. Becausesuch birds as Bonaparte'sand Sabine'sgulls, the Black-legged Kittiwake, and jaegers are not dump-visitingspecies, we must seek a differentexplanation for their increasednumbers in the interior,one that also fits dump-seekerslike the Glaucous-wingedGull. The importanceof reservoirsand associateddam effluentsmay have been underestimatedin comparisonto that of dumps.As earlyas 1960 LaFave(1965 and in AFN 14:327) opined that the reservoirsbehind Columbia River dams were responsiblefor bringingmore andmore raregulls into easternWashington, changingthe statusof the HerringGull from quite rare to regularin winter. The winter gulls at Ft. Peck, Montana, frequent the MissouriRiver just belowFt. PeckDam, wherethey feedon deadfish that havepassed through the turbinesof the hydroelectricplant; the nearestgarbage dump is over 15 miles away at Glasgow(C. M. Carlsonin litt.). G. Berkey (AB 45:121) summarized this effect: "The Missouri mainstream reservoir outlets are great gull feeders,offering ideal conditionsfor the sparsenumbers of raritiesthat musthave overflown the Regionbefore their construction.The collectionobserved at GarrisonDam this fall [1990] was particularlystrik- ing...; 11 of the 12 gull speciesfor North Dakota this seasonwere seen there." Damswithout hydroelectric plants may be lessattractive to gulls,but we presumethat all reservoirshave been stockedwith sportfish, a potential food supply. At many localities,especially near cities,dumps are closeto reservoirs, naturallakes, and/or largerivers, and this we believeis an idealsituation for winteringGlaucous-winged Gulls -- dumpsfor feeding,adjacent water for 180 RANGE EXPANSION OF GLAUCOUS-WINGED GULL drinkingand bathing,and nearbyislands or deep safe watersfor night roosting.The absenceof one or anotherhabitat may significantlyreduce the probabilityof occurrenceand, especially,overwintering of Glaucous- winged Gulls. However, some dam effluentsand reservoirsare equally attractive food sources.

Philopatryand Longevity The Glaucous-wingedGull is partiallyphilopatric in winter, as evidenced by a bird banded11 milesnorth of Merville,British Columbia, on 29 July 1968 that visitedthe samerooftop in San Francisco,California, for seven consecutivewinters, 26 January1970 to 15 January1978 (Binfordpers. obs.).Also, this specieshas livedto the age of 32 and has an averagelife expectancyof 13.5 years(Verbeek 1993). The effectof thesetwo attributes may have changedin recent years. As the number of inland vagrants increases,so does the likelihoodthat some will be philopatric, and the longera philopatricindividual lives, the greaterits chancesof beingjoined by other birds to form a population.We do not know if philopatry is occurringinland, but the presenceof a few adultsthere suggestsit is. Also, Glaucous-wingedGulls presumably are more likely to succeedin returning to localitiescloser to the coast,and in fact six of the eight adults,as well as both third-y•arbirds, were in Albertaand Idaho. How then did population growth, habitat alteration, philopatry, and longevityaffect the Glaucous-wingedGull? Although inland vagrancy has alwaysoccurred, prior to about 1971 fewer vagrantsoriginated from the then smaller coastal breeding colonies; those individualsthat ventured inland found little suitable habitat to sustain them and either retreated quicklyor perishedbefore they couldbe detectedby the scantforce of capableobservers. More recently,however, growth in the coastalbreeding populations,and perhapsthe establishmentof newbreeding colonies along the Columbia River, resultedin more individualswith nomadic tendencies, and populationpressures stimulated a greater percentageof these to disperseinland. These pioneersfound new and improvedinland habitats providedby dumps, reservoirs,and hydroelectricdam effluents,which allowedthem to remain and, with recruitmentfostered by philopatryand longevity,form small winter populationsmore easilydiscovered by the largerarmy of observers.Improved coverage has producedmore records but hasalso masked the effectsof a "natural"process that hasresulted in an increase in the actual number of birds.

SUMMARY

The Glaucous-wingedGull is expandingits winter range eastinto interior statesand provinces(97 acceptablerecords) as well as to inlandlocalities in coastalstates and provinces(many records).This expansionseems due to both slow diffusionalong the ColumbiaRiver systeminto areas(eastern Washington, adjacent Oregon, and northern Idaho) nearest the coastal breedingpopulation, as well as areas (Central Valley and Salton Sea of California)close to the coastalwintering population,and jump-dispersal

181 RANGE EXPANSION OF GLAUCOUS-WINGED GULL directlyover inhospitablemountain ranges to more distantregions (eastern British Columbia and Alberta, Saskatchewan, Manitoba, southern Idaho, Montana, Colorado, Oklahoma, Illinois, Utah, Nevada, Arizona, and New Mexico). Both types of movementoccurred in the past (1912, 1950s, 1960s), but becauseof the scarcityof adequateinland habitat, birds did not remain and hencewere lessdetectable. Newly availablesuitable habitat in the form of reservoirs,hydroelectric dams, and largegarbage dumps has been encounteredby recentbirds, allowing them to remain and thus be more detectable.A burgeoningbreeding population on the coast has resultedin more repeated inland occurrencestarting about 1971 and especiallyduring winter 1988-89. Improvedcoverage by observerscan accountfor only some of this increaseand has maskedthe effectsof "natural"factors. Repeated vagrancy has resulted in recruitment,probably fosteredby philopatryand longevity,producing local winter populations that are smallbut more or lessregular in northwesternSonora, the Central Valley and Salton Sea of California,eastern Washington, north-central Oregon, northernIdaho, Utah, and Nevada.Winter temporaldistribution inlandis similarto that alongthe Californiacoast, with somebirds arriving as early as mid Septemberbut most from late October through mid December,leaving from late Februarythrough early March, and straggling into May; somecontinue to wanderin midwinter.There are nonbreeding summer recordsfor Alberta, Manitoba, interior California, Colorado, and New Mexico, althoughmost winter visitorsinland apparentlysummer on the coast.Starting about 1977 a smallbreeding population established itself along the ColumbiaRiver in easternWashington and Oregon. These last two states,which are nearestthe core breedingpopulation on the Pacific coast,have received the mostbirds and thuswere the firstto supportnew inland wintering and breedingcenters. To monitor further expansionor contractionof the Glaucous-winged Gull'srange, observers are urgedto documentand publishall far-inland sightings.

ACKNOWLEDGMENTS

We thank the followingpersons who kindlyprovided information on Glaucous- winged Gull recordsfrom particularstates and provinces:Alberta, M. Harrison, P. Sherrington;Arizona, T. R. HueIs, J. Witzeman, R. L. Zusi;Arkansas, M. Parker; Colorado, H. E. Kingery,B. Prather;Idaho, T. H. Rogers,D. A. Stephens,S. H. Sturts,C. H. Trost;Illinois, R. E. Goetz; Iowa, C. J. Bendorf, T. H. Kent; Kansas,S. Patti; Louisiana, D. L. Dittmann; Manitoba, P. C. Chu; Minnesota, K. Eckert; Missouri, R. E. Goetz; Montana, C. M. Carlson,P. L. Wright; Nebraska, A. G. Grenon;Nevada, M. Cressman,J. L. Dunn, A. A. Gubanich,H. E. Kingery,M. V. Mowbray,L. A. Neel, C. S. Robbins;New Mexico, R. W. Dickerman,J.P. Hubbard, J. E. Parmeter; New York, R. F. Andrle; North Dakota, D. Buitron, G. Nielsen; Oklahoma, G. D. Schnell;Ontario, B. Curry; Saskatchewan,C. S. Houston; Sonora, S. M. Russell;South Dakota, D. Swanson;Texas, G. Lasley;Utah, D. L. Fischer,L. A. Ryel, E. Sorensen,M. Tove;Wyoming, L. Hunter.We alsoextend our appreciationto D. E. Willardfor accessto librariesof the FieldMuseum of Natural History, Chicago, R. B. Payne for providingpertinent literature,and N. A.M. Verbeek,who revieweda draft of the manuscript.

182 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

LITERATURE CITED

Alcorn, J. R. 1988. The Birds of Nevada. Fairview West, Fallon, NV. AmericanOrnithologists' Union. 1983. Check-listof North AmericanBirds, 6th ed. Am. Ornithol. Union, Washington,D.C. Burleigh,T. D. 1971. Birdsof Idaho.Caxton, Caldwell, ID. Chu, P. C. 1992. Actionsof the MichiganBird RecordsCommittee for 1990 and 1991. Jack-Pine Warbler 69 (5): 17-23. Conover,M. R. 1983. Recentchanges in Ring-billedand Californiagull populations in the western United States. Wilson Bull. 95:362-383. Conover, M. R., and Thompson, B.C. 1984. Inland breedingby the Glaucous- wingedGull. J. Field Ornithol.55:380-382. Crosby,G. T. 1972. Spreadof the Cattle Egretin the WesternHemisphere. Bird- Banding43:205-212. DeSante,D. F. 1973. An analysisof the fall occurrencesand nocturnalorientations of vagrantwood warblers (Parulidae) in California.Ph.D. Dissertation,Stanford Univ., Stanford, CA. DeSante,D. F., and Ainley, D. G. 1980. The avifaunaof the SouthFarallon Islands, California. Studies in Avian Biol. 4. Dickson,R. 1989. Regionalrecords--Calgary. Alberta Bird Record7:23-35. Fischer,D. L. 1988. Firstrecords of the Glaucous-wingedGull in Utah. GreatBasin Nat. 48:298-300. Garrett,K.. and Dunn,J. 1981. Birdsof SouthernCalifornia. Los Angeles Audubon Soc., Los Angeles. Gilligan,J., Rogers,D., Smith, M., and Contreras,A., eds. 1994. Birdsof Oregon. Cinclus, McMinnville, OR. Jehl, J.R. 1974. A specimenof Larus glaucescensfrom HudsonBay. Wilson Bull. 86:168-169. Jensen,R. 1988. Glaucous-wingedGull at Naicam. Blue Jay 46 (1):14-15. Johnson,D. B., Binford, L. C., Stokie, A., and Marcisz,W. 1995. First confirmed Illinoisrecord of the Glaucous-wingedGull. Meadowlark 4:47-50. LaFave,L. D. 1965. Revisedstatus of Laridaein easternWashington. Murrelet 46:7-11. Lawson,C. S. 1973. Charadriiformesnew to Nevada.W. Birds4:77-82. Lawson, C. S. 1977. Nonpasserinespecies new or unusualto Nevada. W. Birds 8:73-90. Merilees,W. J. 1961. FirstAlberta record for the Glaucous-wingedGull. Can. Field- Nat. 75:170. Monsom G., and Phillips,A.R. 1981. AnnotatedChecklist of the Birdsof Arizona, 2nd ed. Univ. Ariz. Press, Tucson. Mundinger,P. C., and Hope, S. 1982. Expansionof the winterrange of the House Finch: 1947-1979. Am. Birds 36:347-353. Payne,R. B. 1983. A distributionalchecklist of the birdsof Michigan.Univ. Mich. Mus. Zool. Misc. Publ. 164. Pinel, H. W., Smith, W. W., and Wershler,C. R. 1991. Alberta birds, 1971-1980, vol. 1, non-passerines.Prov. Mus. Alberta Nat. Hist. Sec. Occ. Pap. 13.

183 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

Reid, W. V. 1988. Populationdynamics of the Glaucous-wingedGull. J. Wildlife Mgmt. 52:763-770. Salt, W. R. 1966. Some unusual bird records from the Peace River District. Can. Field-Nat. 80:114-115. Stirling, D. 1967. Sight record of Glaucous-wingedGull for Alberta. Blue Jay 25:131. Sutton,G. 1938. Glaucous-wingedGull in Oklahoma.Auk 55:277-278. Taylor, D. M., and Trost, C. H. 1987. The statusof rare birdsin Idaho. Murrelet 68:69-93. Tove, M. H., and Fischer,D. L. 1988. Recentchanges in the statusof winteringgull populationsin Utah. Am. Birds42.182-190. Udvardy,M.D. F. 1969• DynamicZoogeography. Van NostrandReinhold, New York. Verbeek,N. A.M. 1993. Glaucous-wingedGull (Larus glaucescens), in The Birdsof North America, No. 59 (A. Poole and F. Gill, eds.). Acad. Nat. Sci., Philadel- phia. Weber, J. W. 1981. The Larus gulls of the Pacific Northwest'sinterior, with taxonomic comments on several forms. Part If--Conclusion. Continental Birdlife 2:79-91. Weber,J. W., and Fitzner,R. E. 1986. Nestingof the Glaucous-wingedGull eastof the WashingtonCascades. Am. Birds40:567-569. Weseloh,D. V., and Lang, V. 1973. Glaucous-wingedGull and Thayer's Gull at Calgary,Alberta. Blue Jay 31:230-232.

APPENDIX. Recordsof the Glaucous-wingedGull from interior states and provincesof North Americathrough 1993. Becausemost records have not receivedformal committeereview and many lack detaileddocumentation, we cannot vouch for their validity.Some, especiallyfrom earlier years, might have been of other speciesor hybrids.All, however,have receivedscreening by at leastone authority,usually the appropriateAmerican Birds regional editor. Possibly,some recordswe treat as separate pertain to the same individualbird seen the sameseason (possibly at differentlocalities) or returningin subsequentyears. On the other hand, we or othershave questionedcertain records that may in fact be valid; for completeness,we list these in brackets,but have not used them to formulate statements in the text. Recordsare listedand numberedchronologically within each state or province. Each individualbird is consideredone "record." Information, if known, includes,in orderof presentation,inclusive dates of occurrence(all years are in the 20th century), locality,number of individualsand their ages,photographic (published photos are in the citedpublications), specimen, or bandingdocumentation (all recordsare sight recordsunless otherwise noted), habitat, comments, and citations. Some •'in litt." citationsfollow the name of the region. Abbreviations.[ ], recordinvalid, or possiblyvalid but not usedby us in text; *, record acceptedby the appropriatestate recordscommittee, an extant specimen identifiedby an ornithologist,or a bandingrecord; AB, American Birds;ad, adult; AFN, Audubon Field Notes; im, immature; mi., miles; MSB, Museum of Southwest- ern Biology, Universityof New Mexico, Albuquerque,NM; NASFN, National

184 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

Audubon Society Field Notes; res, reservoir;UMMZ, Universityof Michigan Museumof Zoology,Ann Arbor,MI; USNM, UnitedStates National Museum of NaturalHistory, Washington, DC.

AI.•E!;ITA (all M. Harrison and P. Sherringtonin litt.): [before 1936; near Calgary;1 im; specimen,since lost (Weseloh and Lang 1973)]. ('1) midSep 58; Bear Lake, northwestof GrandePrairie; 1 2nd-yr;lake; mountedspecimen (Salt 1966). (*2) 11 Aug 59; Bear Lake, northwestof Grand Prairie; 1 3rd-yr; lake; mounted specimen;the statementthat thiswas one of 10-12 presenthere in fall 1959 is not well supported(Salt 1966). (*3) 15 Apr 60; TherienLake southwestof St. Paul;1 lst-yr; lake; banded(597-56837) on ChristieIslet, south of Anvil Island,Howe Sound,British Columbia 19 Jul 59 and foundalive and releasedat Therien Lake; dateof recoverysometimes given incorrectly as 2 Jun60 (Merilees1961). (4) 28 Sep 66; Valleyviewgarbage dump; 1 ad• dump (Stirling1967). (5) 3-4 May 72; Forest LawnSanitary Landfill, Calgary; 1 ad; dump;unpublished photographs (AB 26: 776; Weselohand Lang1973). (6) 2 Oct 76; Legal;! im (Pinelet al. 1991). (7) 5 Apr 80; alongBow River,Calgary; 1 2nd-yr;river (AB 34:788; Pinelet al. 1991). (8) 6-21 Aug 83; NamakaLake, about10 mi. SE of Strathmore;1 im (AB 38:215). (9) 9 May 84; alongBow River, Calgary; 1 lst-yr;river (AB 38:926). (10) 3-10 Nov 84; along Bow River,Calgary; 1 lst-yr• river (AB 39:68). (11) 17 Apr 85; alongBow River, Calgary;1 im; river(AB 39:316). (12) 6-14 Nov 88; alongBow River,Calgary; 1 im; river;unpublished photos (Dickson 1989). (13) 3 Apr 90; alongBow River,Calgary; 1; river (AB 44:446). (14) 21 Mar 92; along Bow River Calgary; 1 lst-yr; river; unpublishedphotos (AB 46:438-439). ARIZONA (all J. Witzeman in litt.): ('1) 4-24 Feb 54; Lake National Wildlife Refuge, Bill WilliamsArm, lower Lake Havasu; 1 lst-yr; res; female specimen (USNM 481196)(AFN 8:263; Monsonand Phillips1981; R. L. Zusiin litt.). (*2) 17 Nov 56; 8 mi. aboveImperial Dam and 1 mi. belowYuma Wash on ImperialNational WildlifeRefuge; 1 lst-yr; river; unsexedspecimen (University of Arizona,Tucson, 4913) (AFN 11:48; Monsonand Phillips1981; T. R. HueIs in litt.). (*3) 12 Dec 74- 18 Feb 75; belowDavis Dam; 1 lst-yr; river;also recorded in Nevada(AB 29:725). (*4) all winter75-76; belowDavis Dam; 1 2nd-yr;river; also recorded in Nevada(AB 30:750). (*5) 30 Oct 81; Lake HavasuCity; 1 lst-yr; res (AB 36:204). COLOIIADO (allB. Pratherin litt.): [21 Oct 56; MarstonLake; 1 im; lake;said to be a new speciesfor Colorado;not reviewedby state recordscommittee, as no documentationavailable (AFN 11:36)]. [24 Nov 56; South PlatteRiver in Denver; 1; river;not reviewedby staterecords committee, as no documentationavailable (AFN 11:36)]. ('1) 24-25 Jul 81; Antero Reservoirnear Hartsell; 1 lst-yr; res. (*2) 31 Mar-6 Apr 89; JulesburgReservoir west of Julesburg;1 lst-yr; res(AB 43:515). (*3) 11-19 Apr 89; CherryCreek Reservoir, Denver area; 1 2nd-yr;res; published photo (AB 43:515, 516). (*4) 1 May 90; Cherry Creek Reservoir,Denver area; 1 2nd-yr, molting;res. (*5) 1 Mar-1 Apr 92; Cherry Creek Reservoir,Denver area; 1 lst-yr; res (AB 46:455). IDAHO: (1) 17-23 Feb 63; SpokaneRiver, Coeur d'Alene; 1 im; river;unpub- lishedphoto (J. Acton)(AFN 17:344; Burleigh1971; LaFave1965; Weber1981; S. H. Sturtsin litt.). (2) 1 Jan 65; Coeur d'Alene Landfill(Ramsey Rd.); 1; dump (AFN 19:403; S. H. Sturtsin litt.). (3) 16 Feb-8 Mar 75; SpokaneRiver and CougarBay. Coeurd'Alene; 1 im; riverand lake;possibly two differentindividuals (AB 29:718: S. H. Sturtsin litt.). (4) 4 Dec 76; SpokaneRiver, Coeur d'Alene; 1 1st -yr; river (S. H. Sturtsin litt.). (5) 29 Jan-5 Feb 77; Spokane River and Coeur d'Alene Landfill (RamseyRd.); 1; riverand dump(S. H. Sturtsin litt.).(6) 28 Dec 77; Coeurd'Alene area; 1 ad (AB 32:378; Weber 1981; S. H. Sturtsin litt.). (7) 17 Feb 78; Nampa: 1 (AB 32:378; Taylorand Trost 1987; Weber 1981). (8-10) 14 Feb 87; CougarBay.

185 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

Coeurd'Alene Lake; 1 ad, 1 lst-yr, 1 3rd-yr;lake (AB 41:306; C. H. Trostand S. H. Sturtsin litt.). (11) 2-7 Jan 89: Coeurd'Alene Landfill (Ramsey Rd.): 1 lst-yr; dump (AB 43-343; C. H. Trost and S. H. Sturtsin litt.). (12) 4 Nov 89: Wolf Lodge Bay, Coeur d'Alene Lake; 1 ad; lake (AB 44:129• S. H. Sturts in litt.). (13) 1 Jan 90: Coeurd'Alene Landfill (Ramsey Rd.); 1 lst-yr;dump (S. H. Sturtsin litt.).(14) 13 Dec 90• Coeur d'Alene area; 1 (AB 45:295; C. H. Trost and S. H. Sturtsin litt.). (15) 1 Dec 91: Coeur d'Alene Landfill(Ramsey Rd.); 1 lst-yr; dump (AB 46:291; C. H. Trostand S. H. Sturtsin litt.). (16) 4 Jan 92; Boise;1 lst-yr (AB 46:291: C. H. Trost in litt.). (17) 18 Nov 92-8 Feb 93; Coeur d'Alene Landfill(Ramsey Rd.); 1 lst-yr: dump (AB 47:122,279; S. H. Sturtsin litt.). (18) 26 Oct 93• near dam in WillowBay on American FallsReservoir; 1 ad; res (NASFN 48:131; C. H. Trost in litt.). (19) 30 Oct-ll Nov 93: Coeur d'Alene Landfill(Fighting Creek); 1 lst-yr• dump: unpublishedphotos; possibly two differentindividuals (NASFN 48:131, 229: C. H. Trost and S. H. Sturtsin litt.). (20) 17 Dec 93; Coeurd'Alene Landfill(Fighting Creek): 1 2nd-yr; dump (NASFN 48:229; S. H. Sturtsin litt.). (21) 17 Dec 93-16 Jan 94; Coeur d'Alene Landfill(Fighting Creek); 1 2nd-yr' dump (NASFN 48:229; S. H. Sturtsin litt.). (22-23) 25 Jan 94; Colburn(Bonner Co.) Landfill; 1 lst-yr and 1 unknown;dump (NASFN 48:229; S. H. Sturtsin litt.). ILLINOIS. [18-25 Feb 89; Peoriaarea; 1 ad; river:under review by staterecords committee].('1) 27 Nov-12 Dec 92; Chicago;1 2nd-yr:two riversand two dumps: video and publishedphotos (AB 47:101-102, 169: Johnsonet al. 1995). [27-28 Feb 93; Peoria Lock and Dam; 1 3rd-yr; river: under review by state records committee (AB 47:263-264)]. [19-20 Feb 93• Lake Decatur: 1 3rd-yr: lake at warm-wateroutlet• under reviewby state recordscommittee (AB 47:263-264)]. MANITOBA: ('1) 1 Jun 64• Churchill; 1 2nd-yr: female specimen (UMMZ 211531) (Jehl 1974: P. Chu in litt.). I•ICHIGAN: [19 Dec 70; St. Joseph;1; listedas hypotheticalby Payne(1983) and rejectedby staterecords committee (Chu 1992)1. I•ONTANA (all C.M Carlson in litt.): [1 Jan 55: Great Falls: 1• no description availableto staterecords committee and not includedin recentMontana publications (AFN 9:272)]. ('1) 21 Mar-6 Apr 85; MissouriRiver just below Ft. Peck Dam. 1 lst-yr; river at dam; publishedphoto (AB 44:450). (2) 26 Jan 91; Polsondump near FlatheadLake; 1 lst-yr; dump (AB 45:295). (3) early Nov 91; Polsondump near FlatheadLake; 1 lst-yr; dump(AB 46:125). (*4) 7 Dec 91-18 Apr 92: Missouri Riverjust below Ft. PeckDam; 1 lst-yr; riverat dam; publishedphoto (AB 46:282, 441). NEVADA: (1-3) 30 Oct 71-27 Feb 72; [.as VegasBay, Lake Mead;up to 3 lst- yr presentduring period; res; a fourthbird, collected 11 Feb 72, wasa Thayer'sGull (AB 26:101,639, 888; Alcorn 1988; Lawson1973: M. V. Mowbrayin litt.). (*4)late Jul 72; 1 mi. from eastshore of Lake Tahoe near Glenbrook:1 lst-yr: inland;banded (967-19765) 8 mi. NW of Torino,Vancouver Island, British Columbia 11 July 1971 (not 1972 as in Alcorn 1988); becausebird found as a disarticulatedskeleton, recove• date meansnothing (Alcorn 1988; Lawson1973: C.S. Robbinsin litt.). (5) Nov, 16-28 Dec 72; LasVegas Bay, Lake Mead; 1 lst-yr: res(AB 27:648; Alcorn 1988; Lawson1973; M. V. Mowbrayin litt.). (6) 15 Dec 73: Las VegasBay, Lake Mead; lst-yr; res (M. V. Mowbrayin litt. ). (7-8) 30 Nov 74: BoulderBeach, Lake Mead; 2 lst-yr; res(AB 29:94; Alcorn 1988; Lawson1977; M. V. Mowbrayin litt.). (9) 12-18 Dec 74, 18 Feb 75; belowDavis Dam; 1 lst-yr; river:seen also in Arizona (Alcorn1988; Lawson1977). (10) 4 Dec 75; CottonwoodBasin, Lake Mojave: 1: res (Alcorn 1988; Lawson 1977). (11) 9-29 Jan 76; below Davis Dam; 1 2nd-yr; publishedphoto; river; seen also in Arizona (Alcorn 1988: Lawson 1977; M. V. Mowbrayin litt.). (12) 14 Nov 76; Las VegasBay, Lake Mead: 1 lst-yr; res (AB 186 RANGE EXPANSION OF GLAUCOUStWINGED GULL

31:205• Alcorn 1988: Lawson1977; M. V. Mowbrayin litt.). (13-14) 17-22 Jan 78; LasVegas Bay, LakeMead: 2 lst-yr•res (AB 32:381: Alcorn1988: M. V. Mowbray in litt.). [summer 79: Lahontan Reservoir; 7: res; the number of individualsand summerdate make us suspectthese were worn fadedindividuals of anotherspecies (Alcorn1988)]. (15) 7 Dec 80-21 Feb 81; Las VegasBay, Lake Mead: 1 lst-yr; res (AB 35:322; Alcorn 1988; M. V. Mowbrayin litt.). (16) 19 Nov-19 Dec 81: Las VegasBay. Lake Mead; 1 lst-yr: res;with #17 on 19 Dec (AB 36:202; Alcorn 1988). (17) 19 Dec 81: LasVegas Bay, Lake Mead; 1 lst-yr; res;with #16 on 19 Dec (M. V. Mowbrayin litt.).(18) 27 Mar 88; WalkerLake: 1• lake(AB 42:468). (19) 19 Dec 88; LasVegas Bay, Lake Mead: 1 lst-yr:res (M. V. Mowbrayin litt.).(20) 24 Nov 90; Lake Mead marina: 1 lst-yr: res (AB 45:133• M. V. Mowbrayin litt.). [10 Jan 91; Lake Mead: 1: res;no descriptionand not publishedin AB (H. E. Kingeryin litt.)].(21) 21 Oct 91; Mud Lake: 1 (AB 46:128). (22) 26 Nov 91-4 Jan 92; PyramidLake; 1• res; three other birdsat PyramidLake duringwinter 91-92 consideredof questionable identityin AB (AB 46:128. 293, 295). (23) 3 May 92; Reno: 1 (AB 46:455). (24) 1 Jan-22 Feb 93; Reno; 1 (H. E. Kingeryin litt.). (25) 18 Dec 93-9 Jan 94: Virginia Lakein Reno: 1 2nd-yr:res (L. A. Neel in litt.).(26) 10 Feb94: VirginiaLake in Reno; 1 lst-yr; res(L. A. Neel in litt.).(27) 11-15 Nov 94: LasVegas Bay, LakeMead: 1 lst- yr; res;unpublished photos seen by us(M. Cressmanand M. V. Mowbrayin litt.).(28) 19 Nov 94; VirginiaLake in Reno; lst-yr: res (L. A. Neel in litt.).

NEW MEXICO: [10 Jan 54 (not 1 Jan): Lee Ranch, 30 mi. N of Grants: 1 ira: flyingover land:description too incompleteto eliminateother forms(AFN 8:263: J. P. Hubbardin litt.)]. [31 Dec 55: Roswell:7: ChristmasBird Count; no details(AFN 10:206: J.P. Hubbard in litt.)]. (•1) 21-24 Jan 90, Caballo Lake, and 7 Feb, 7 Mar 90, ElephantButte Lake: 1 2nd-yr:both res; two photos(New Mexico Ornithological Society#1990-11A-B) from CaballoLake, one published;female specimen(MSB 8650); here presumedto be the same bird on all dates(AB 44:306; J.P. Hubbard and R. W. Dickermanin litt.). (*2) 12 Feb-3 Oct 94; ElephantButte Lake; 1 lst-yr (2nd-yrwhen collected):res; unpublishedphotos: male specimen(MSB 18929); a possibleGlaucous-winged at CaballoLake 16 Jan and 6 Feb 94 mighthave been same bird (NASFN 48:236. 328: J. E. Parmeter and R. W. Dickerman in litt.). NORTH DAKOTA: [30 Oct 90: belowGarrison Dam nearRiverdale: 1 3rd-yror ad; river; 10 unpublishedphotos: state recordscommittee has made no final dispositionbut tends toward rejection (D. Buitronand G. Nielsenin litt.)].[30 Sep-4 Nov 90; GarrisonDam: 1 2nd-yr;not yet reviewedby staterecords committee (AB 45:121)]. OKLAHOMA: ('1) 15 Feb 12: Capron; 1 ad; unsexedmounted specimen (NorthwestState College, Alva, Oklahoma, 0112) (Sutton 1938; G. D. Schnellin litt.). SASKATCHEWAN:[19 Dec87:3 kmwest of Naicam;1 ad:described as having yelloweyes and white head. so we consideridentity questionable (Jensen 1988, C. S. Houstonin litt.)].(1) 9-16 Nov 91: GardinerDam; 1 2nd-yr:res (AB 46:109; C. S. Houston in litt.). UTAH: (1) 19 Dec 83: SaltLake City Landfill: 1 lst-yr;dump; unpublished photos usedafter originalidentification as Thayer'sGull (M. Tove in litt.). (*2) 20 Nov-19 Dec 84; near ProvoDump and SaltLake City Landfill:1 lst-yr; dumps;published photo(AB 39:84; Fischer1988: M. Toveand D. L. Fischerin litt.).(*3) 7 Dec 84-26 Feb85: OremDump and Salt Lake City Landfill; 1 lst-yr:dumps, unpublished photo (Fischer1988; M. Tove and D. L. Fischerin litt.). (*4) 19 Jan-4 Feb 85; Salt Lake City Landfill;1 lst-yr: dump.unpublished photo (Fischer1988; M. Toveand D. L. Fischerin litt.).(*5) 26 Feb-13 Mar 85: BountifulArea RefuseDump, south shore of

187 RANGE EXPANSION OF GLAUCOUS-WINGED GULL

FarmingtonBay; 1 lst-yr; dump(Fischer 1988; M. Toveand D. L. Fischerin litt.). (*6) 30-31 Mar 85; near ProvoDump; 1 lst-yr; near dump,unpublished photo (AB 39-331; Tove and Fischer 1988; Fischer 1988: M. Tove and D. L. Fischerin litt.). (7) 20 Nov 85; ProvoDump and Salt Lake City Landfill;1 2nd-yr;dumps (AB 40.-147; Fischer 1988; Tove and Fischer 1988). (8) 7-18 Dec 85; BountifulArea Refuse Dump, southshore of FarmingtonBay; 1 lst-yr; dump(AB 40:308; Fischer1988; M. Tove in litt.). (9) winter 85-86; region of Salt Lake City; 1 lst-yr; dump (AB 40:308; Fischer1988; Tove and Fischer1988). (10) winter 85-86; region of Salt Lake City; 1 lst-yr;dump (AB 40:308; Fischer1988; Toveand Fischer1988). (11) 10 Nov 89; Logan;1 lst-yr; sewageponds; unpublished photos (AB 44:131; L. A. Ryel in litt.). (12) 28 Dec 90; Salt Lake City Landill;1 ad; dump;unpublished photo (E. Sorensenin litt.). (13-14) winter 1993-94; Salt Lake City Landfill;2; dump; unpublishedvideotape (NASFN 48:231). Accepted 24 August 1995

Glaucous-wingedGull, 11-15 November1994, LakeMead Marina, LasVegas Bay, Lake Mead. Nevada. Photo by Marian Cressman

188