j. Field Ornithol., 59(1):13-21

THE SNOWY PLOVER IN SOUTHEASTERN OREGON AND WESTERN NEVADA

STEVEN G. HERMAN Malheur Bird Observatory and The EvergreenState College Olympia, Washington98505 USA JOHN B. BuLgER Divisionof EnvironmentalStudies Universityof California Davis, California95616 USA JOSEPHB. BUCHANAN ldO9 W. Seventh Avenue Olympia, Washington98501 USA Abstract.--In 1980, we searchedfor SnowyPlovers (Charadrius alexandrinus) in an area of 130,000km 2 in southeasternOregon and westernNevada. We found2016 adult Snowy Ploversat 23 sites.Plovers were consistentlyassociated with water and occurredon bareor sparselyvegetated alkaline substrates.We found 72 nests;nesting was documentedat all but 3 sites.One hundredand fifty-four broodswere foundand broodsize averaged 2.4 in youngerbroods, 1.6 in older broods.In the 1980s,rising water levelsin the northernGreat Basin eliminatedmuch Snowy Plover nestinghabitat.

EL PLAYERO CHARADRIUS ALEXANDRINUS EN LA PARTE SURESTE DE OREGON Y EL OESTE DE NEVADA Resumen.--Duranteel 1980 examinamosun fircade 130,000km 2 en el surestede Oregon y oestede Nevadaen bfisquedadel playeroCharadrius alexandrinus. Encontramos 2016 aves adultasen 23 localidades.Pudimos asociar consistentemente losplayeros con agua y estos aparecieronen sustratosalcalinos desnudos o parcialmentecubiertos con vegetaci6n.En- contramos72 nidos en todas las 1ocalidadesa excepci6nde 3 de (•stas.Un total de 154 parvadasde polluelosfueron localizadas. E1 tamafiopromedio de las parvadasvari6 conla edadde lospolluelos. En avescon edad menor a 15 dias,el tamafiopromedio de la parvada result6ser de 2.4 individuosmientras queen polluelosmayores de 15 diasse redujo a 1.6. Un aumentoen el nivel del aguadurante el 1980 elimin6gran parte del habitaci6nde anidamientode estosplayeros en la Gran Cuencadel notre.

Ornithologistshave been remarkably slow to discoverthe patternsof distributionand abundanceexhibited by SnowyPlovers (Charadrius al- exandrinus)in westernNorth America.Interior populationsin Nevada andOregon were especially slow to cometo light (Linsdale1936, Marshall 1969).In the early1970s ornithologists suspected that the SnowyPlover had becomerare overmuch of its rangein North America,and concern aboutits statuswas expressedin severalplaces, including the National AudubonSociety's "Blue List" (seeArbib 1971).Recognizing the dearth of informationon the distributionand abundanceof the species,we censusedSnowy Ploversin southeasternOregon and western Nevada during the spring and summerof 1980.

13 14] S.G. Herman et al. J.Field Ornithol. Winter 1988

STUDY AREA AND METHODS Between21 Apr. and 31 Jul. 1980, we spent 73 d searchingfor, counting,and observingbreeding populations of Snowy Ploversin an area coveringnearly 130,000 km2 of the northwesternGreat Basin (Fig. 1); after completingthe initial surveywork, we gatheredadditional data on 12 d between 1 Aug. and 5 Sep. Working from United StatesGeo- logicalSurvey topographic maps, our own experienceand that of other observers,and the literature, we selectedand checkedapproximately 150 sitesfor suitable habitat and Snowy Plovers.Sites without appropriate habitat were in some cases eliminated from further consideration after we observedthem from the air. Most naturally occurringalkaline ponds and lakes, as well as artificial impoundmentsthat constitutedequivalent habitat, were surveyedon foot. At least two observersworked at each site;as many as 14 additionalpeople assisted us in areaswhere the habitat was extensive.We recordednumbers and age classesof Snowy Plovers at all siteswhere we found them. Most sitesthat supportedplovers were visited at least twice, as were areas with suitable habitat where we failed to find the specieson our initial visit. In all placeswhere Snowy Plovers were present,we attemptedto documentnesting, but we did not always make intensive searches for nests. When nests were found we recorded clutch size and describedthe nesting substrate.When broods were en- counteredwe countedthe number of young and estimatedchick size by comparingwith adults.We gatheredinformation on physicalcharacter- istics,vegetation, and other habitat componentsat all sites.

RESULTS We found 2016 adult Snowy Ploversin the study area with 1047 of them at 11 sites in southeasternOregon and 969 at 12 sites in western Nevada (Table 1, seeFig. 1). Candidatesites where neitherSnowy Plovers nor appropriatehabitat were found are listedin an unpublishedreport depositedin the van Tyne Library at the Museumof Zoology,University of Michigan (Ann Arbor, Michigan 48109). Sites ranged in elevation from 1180 m to 1681 m. Ploverswere consistentlyassociated with water and occurredon bare or sparselyvegetated alkaline substrates.Grease- wood (Sarcobatusvermiculatus), saltbush (Atriplex spp.), seablite(Sueada spp.),and saltgrass(Distichlis stricta) dominate the vegetationthat grows alongthe marginsof the alkaline bodiesof water that supportedSnowy Plovers.Freshwater lakes and ponds,even those with extensivemudflats or sand beaches,did not support Snowy Ploversin the study area; dry alkali flats were similarly without plovers. SoutheasternOregon.--Of the 1047 ploverswe countedin southeastern Oregon,all but 6 (< 1%) occurredwithin 4 majorinternal drainage basins. Harney Basin supported42% (n = 436) of the total, Lake Abert 33% (n = 345), Summer Lake Basin 18% (n --- 193), and Alvord Basin 6% (n = 67). Harney Lake, where we found400 SnowyPlovers, is filled primarily • BUR%•• •'.•'•HARNEY•'AKE SCHOOLHOUSE LAKE •S O•LKALILAKE UMM•LAKE KEABERT OALVORD HOT SPRINGS ALVORDLAKE LOWER BORAX LAKE •AKEVIEW0RE G 0 N HE VA DA

o ALKALI LAKE

•0 •o 40 WINNEMUCCA.r• i KILOMETERSMII.-E'$

NUMBER OF ADUI..T SNOWY PLOVERS .•7'-•1.•0 I.•9-.•56 0 6• - I.•,•' 0 LOWERP,-TF,o I

17' -._T,.• 0 /o•UMBOLDT SLOUGH FER•EY S• 0 •10 • )STILLWATER •RE•O •ND B• v WMA.• N.WR

FIGURE1. Geographicdistribution of breedingsites and relative abundance of adultSnowy Ploversin southeasternOregon and westernNevada during 1980. 16] S. G.Herman et al. J.Field Ornithol. Winter 1988

TABLE1. Distribution and abundanceof adult SnowyPlovers in southeasternOregon and westernNevada during spring and summer, 1980.

Number of Elev. Site adults Date (m) County Lat. L•ng. SoutheasternOregon Harney Lake 400 5 Jun. 1244 Harney 43ø14' 119007' Silver Lake 25 9 Jul. 1257 Harney 43022' 119024' Stinking Lake 9 29 May 1254 Harney 43019' 119021' BacusLake 2 29 Jul. 1248 Harney 43ø16' 118045' Alvord Hot Spring 28 17 Jul. 1222 Harney 42033' 118031' Borax Lakes 24 16 Jul. 1234 Harney 42020' 118036' Alvord Lake 15 16 Jul. 1228 Harney 42023' 118036' Alkali Lake 6 4 Jun. 1306 Lake 42058' 120002' Lake Abert 345 3 Jun. 1297 Lake 42038' 120ø13' SchoolhouseLake 27 15 Jun. 1265 Lake 42058' 120043' Summer Lake 166 15 Jun. 1264 Lake 42050' 120045' Western Nevada Alkali Lake 5 19 May 1681 Washoe 41042' 119051' Lower Pitt-Taylor Res. 12 20 Jun. 1260 Pershing 40038' 118ø16' Stillwater NWR & WMA 344 23 Jun. 1185 Churchill 39037' 118027' Carson SinkI 147 27 Jun. 1180 Churchill 39043' 118041' Carson Lake 144 22 Jun. 1191 Churchill 39019' 118043' Humboldt Slough 4 27 Jun. 1183 Churchill 39050' 118047' Pond A 2 17 26 Jun. 1199 Churchill 39033' 118046' Pond B2 14 26 Jun. 1201 Churchill 39033' 118047' Pond G2 1 27 Jun. 1180 Churchill 39046' 118045' Fernley Sink 126 29 Jun. 1223 Lyon 39038' 119008' Artesia Lake 112 29 Jun. 1386 Lyon 38057' 119017' Walker Lake1 43 28 Jun. 1212 Mineral 38043' 118045'

i Incompletesurvey. 2 Not named on U.S.G.S. maps. by overflowfrom Malheur Lake, a large marsh to the east,via a channel that crossesprivate irrigated land. A small amount of water also is con- tributedby Silver and Warm SpringsCreeks, which enter Harney Lake on the west sidethrough the Warm SpringsValley. Streamwaterreaches the lakebed only during years when it is available from other parts of Malheur National Wildlife Refuge (NWR), either becauseit is excess on thoseparts where it is usedin waterfowl management,or becauseit is not neededto irrigate the private land alongthe channelfrom Malheur Lake. In manyyears the playais essentiallydry by early summer.In dry yearsthe ploversaggregate around a numberof upwellingthermal springs on the playa. These springswere especiallyimportant during 1976-1979. The lake was as full as we have seen it in 1980, and most of the thermal springs were submerged;Snowy Plovers were distributed around the entireplaya perimeter,except for the southwestshore, where densevege- tation bordered the waterline. The 345 Snowy Ploverswe countedat Lake Abert, Lake County, on 3 Jun. constitutedthe secondlargest populationin Oregon. The Che- Vol.59, I•o. I Distributionand Abundance ofSnowy Plovers [ 17 waucan River, which enters Lake Abert at the south end, is the primary sourceof water to this large lake. In yearsof high water, such as 1980, plover habitat is availableonly on the extensivealkali flat on the north and northwestsides of the lake. We found the birds principally alongthe waterline and at two groupsof springsat the north end. Two localitiesin the Summer Lake Basin, in western Lake County, accountedfor 195 Snowy Plovers.Schoolhouse Lake, on the east sideof SummerLake Water ManagementArea (WMA), is part of an extensive alkaline marsh that has formed at the mouth of the Ana River on the north end of the SummerLake playa. We found 27 ploversthere on 15 Jun., the same day we censusedall of Summer Lake. Probably birds move freely between SchoolhouseLake and Summer Lake playa. At SchoolhouseLake, the ploversoccurred primarily on the alkali flats on the east and southwest.The specieshas been reported at Summer Lake WMA by Marshall (1969) and Ramsey(1978). The Summer Lake playa was about half coveredwith water when we censusedit in mid-June• the east half was dry. All but 16 of the 166 Snowy Ploverswere at the south end. The Alvord Basin, in southernHarney County, supported67 Snowy Ploversat three sites.Twenty-eight of thosewere found on the west edge of the Alvord Desert, where water from Alvord Hot Spring forms a series of shallow poolsbefore disappearingon the playa. We found 15 plovers alongthe eastshore of Alvord Lake, which was nearly full as late as the end of July. The remaining24 Snowy Ploversin the Alvord Basinwere at two sitesin the vicinity of the Borax Lakes; 12 at a small pond 0.8 km eastof Lower Borax Lake Reservoir,and 12 at a spring 1.5 km north of Borax Lake. WesternNevada.-- In westernNevada, 69% of the 969 Snowy Plovers occurredin Lahontan Valley, the area that surroundsFallon in Churchill County; Carson Lake, Stillwater Marsh, and Carson Sink were the pri- mary sites.Fernley Sink, adjacentto the west sideof Lahontan Valley, supported13% (n = 126) of the Nevada total, and Artesia Lake, at the north end of Smith Valley in Lyon County, accountedfor 12% (n -- 112). Other sites included Walker Lake (4%; n = 43), Lower Pitt-Taylor Reservoir (1%; n = 12), and Alkali Lake (1%; n = 5). Lahontan Valley is the singlemost important area for Snowy Plovers in the stateof Nevada. Prior to the early part of this century,the Carson River entered the valley from the west and flowed east, terminating in extensive alkaline marshes and sinks at three main outflows; Carson Lake, Stillwater Marsh, and CarsonSink. In responseto increasedagricultural use of the valley, the U.S. Bureau of Reclamationcreated the Truckee- Carson Irrigation District, an administrativebody that, since 1911, has presidedover the constructionof damsand diversioncanals that distribute availablewater in a designthat servesirrigated farming almost exclusively. Today, water reachesCarson Lake, Stillwater Marsh, and Carson Sink onlywhen it is not takenfor irrigation.Consequently, seasonal and annual fluctuations of water levels are extreme and unpredictable. When we 18] s. G.Herman et al. J.Field Ornithol. Winter 1988 surveyedthese sites in late June, most storagereservoirs were at or near capacity,and water was beingreleased from them as rapidly as possible. Water levelsin the vicinity were as high or higher than they had been for many years. More than half of the Snowy Plovers in the Lahontan Valley were found on the Stillwater WMA and Stillwater NWR. Of the 344 plovers we counted there, all but six occurred on the eastern half of the Stillwater Marsh. Severalrecords of Snowy Ploversat Stillwater Marsh have been published:Alcorn (1946) collectedspecimens there on three datesin Aug. 1941. Marshall (1951) reportedhaving seen50 at Big Water on 20 Jul. 1950, and severalhundred there on 8 Aug. 1950. He also found three nestsat the northeastcorner of the marsh in mid-June 1951 (Marshall and Alcorn 1952). During the summersof 1949 and 1950, Marshall (1951) sawthe species on the perimeter of Pelican Island Marsh at the south end of Carson Sink. Carson Sink was dry when we first visitedLahontan Valley in late April, but was floodedover an area of more than 200 km by late June. We surveyed8 km of the waterline at the southend of the sink, an area that includes the mouth of the Carson River and Pelican Island Marsh, and found 147 adult Snowy Plovers. CarsonLake, at the southend of the valley,also received large amounts of water in late May and June, limiting suitableplover habitat to the southwestportion of the lakebed,which held 144 Snowy Plovers. FernleySink is in northeasternLyon County,adjacent to the Lahontan Valley. Evenden (1952) recordeda flock of about 40 Snowy Plovers, includingone downy chick, at this site on 30 Aug. 1949. We found 126 birds there (including24 at the upper pond of Fernley WMA, 1.5 km south). At the time of our visit about 10 km of the sink was flooded,and the ploverswere distributedalong the southwaterline where water seeps onto the flat from the Fernley WMA ponds. We found 112 SnowyPlovers at Artesia Lake in westernLyon County. Ninety-oneof thosewere on the broadalkali flat at the eastand northeast sidesof the lake, and the remaining 21 were along the west shore.The lakebedwas about 60% floodedin late June. At Walker Lake, the southernextent of our study area, we found 43 Snowy Ploverson the flats at the southend of the lake. Portionsof the eastshore also appeared habitable by plovers,but we did not checkthat area. Linsdale (1956) mentionedone recordof the speciesnear the mouth of the Walker River at the north end of the lake; high water levelsat the time of our visit had eliminated potential habitat there. Publishedrecords of Snowy Ploversexist for three additionalsites in western Nevada. Alcorn (1942) found a dead Snowy Plover on 26 July 1941 at Soda Lake, 10 km west of Fallon; when we visited that site in late April and in June, it was too full of water to supportany shorebirds. One bird was seenat the mouth of the Truckee River, Pyramid Lake, on 19 Apr. 1942 (Linsdale 1951). We searchedthat locationon 50 Jun. and found no plovers.We suspectthat the speciesmay occur on the northwestside of Pyramid Lake, but effortsto obtainpermission to search Vol.59, No. I Distributionand Abundance ofSnowy Plovers [ 19 that area were not successful.Evenden (1952) saw a flock of 300 Snowy Ploversat Toulon Sink, southernPershing County, on 30 Aug. 1949. SnowyPlovers probably occur there and at neighboringHumboldt Sink in most years, but during 1980 runoff from the Humboldt River had floodedthose sites, eliminating suitable nestinghabitat. Nests,eggs, and young.--We documentednesting (by finding eggs,or preflightjuveniles) at all sitesexcept Alkali Lake in Oregon,and Alkali Lake and unnamedpond C in Nevada.We suspect,however, that Snowy Plovers nestedat both Alkali Lakes in small numbers. The corrugated topographyof thesetwo sitesdiscouraged exhaustive searching, and our countswere made beforejuveniles could have been expected. We found 72 nests; 70 of those had complete clutches.Two eggs occurredin six nests,three eggsin 63 nests,and four eggsin one nest (• = 2.93, SD = 0.31). On the southeastshoreline of Harney Lake, where we found 46 nests,we measuredthe distancesbetween concurrentlyactive nests.Distances between 15 pairs of nestsranged from 12 to 63 m (• = 35.7, SD = 14.07); in two of these cases,2 nestswere within 15 m of each other. At Harney Lake we made routine searchesfor nestsfrom 21 Apr. through 11 Aug. The first clutchwas completedon 26 Apr.; the final two nestingattempts we discoveredwere initiatedduring the first week of July. Eggshatched from the last week of May until the end of July. The peak of egg laying occurredfrom mid-May to mid-June; hatching peakedduring June and early July. These findingsare quite similar to thoseof Page et al. (1983) who, working at Mono Lake in California, southwestof the southern extent of our study area, found that Snowy Plover eggswere laid between18 Apr. and 15 Jul. and that hatching occurredbetween 21 May and 16 Aug. We observed154 broodsin the studyarea, and have data on age class and broodsize for 141. Of those,111 were composedof chicksjudged to be lessthan 15 d old (•/5grown); brood size was three in 52% (n = 58) of the cases,two in 34% (n = 38), and one in 14% (rt = 15) (.• brood size = 2.39, SD = 0.72). Among 30 broodswith chicksmore than half grown, 10% (n = 3) includedthree chicks,37% (n = 11) includedtwo, and 53% (n = 16) were singles(.• brood size = 1.57, SD = 0.68). The age-relateddifference in brood size was significant(t = 5.63, P < 0.0005, two-samplet-test) and probablyresulted from chickmortality. Although only two of 72 nestsfell prey to predatorswe suspectthat predationof chickswas more frequent.We found evidenceof preda- tion of a ploverchick by a coyote(Canis latrans) at Walker Lake and ob- servedpredator avoidance behavior by SnowyPlovers whenever a Log- gerheadShrike (Lanius ludovicianus)or a low-flying California Gull (Laruscalifornicus) appeared. Page et al. (1983) foundthat predationof both clutchesand broods was substantial at Mono Lake, California.

DISCUSSION We feel that we searchedthe study area thoroughlyand that our total of 2016 adult SnowyPlovers represents a high percentageof the number 20] $. G.Herman et al. j. FieldOrnithol. Winter 1988 present in 1980. The only large area we did not search was in the contiguousSmoke Creek, San Emidio, and Black Rock desertsof Washoe County, Nevada; somethermal springsand the Quinn River sump may supportsmall, isolatedpopulations. During spring and early summer of 1980, the western Great Basin receivedan unusuallylarge amount of precipitation,and temperatures were lower than usual. As a result of directrainfall and protractedrunoff from higher elevations,most siteswe examined retained water well into the nestingseason. Some sites that normally are without water may have been uniquely available for nestingin 1980. Other playas, where water is normally presentthroughout the year, were floodedto such an extent that suitablenesting habitat was unavailablein 1980; in this latter cat- egory we suspectthe following sitesmay have been included:Malheur Lake, portionsof Summer Lake WMA, Warner Lakes,Goose Lake, and Tumtum Lake in Oregon, and northwestWashoe County Lakes, Con- tinental Lake, Rye Patch/Pitt-Taylor Reservoirs,Humboldt and Toulon Sinks, Indian Lakes, Soda Lakes and someLahontan Valley reservoirs in Nevada. This speciesappears well adapted to annual and seasonal changesin habitat availability for nesting.The population of the study area might expand or contractunder different regional water level con- ditions, but we would not anticipate any significantchange in overall abundancein any but the mostsevere drought or high water years (see below). Our impressionis that this populationis healthy; certainly it is much larger than we had expected. Most areas that we consideredsuitable habitat supported nesting Snowy Plovers. The most seriousthreats to habitat are diversionof water for irrigation, high water conditions(Snowy Plovershave not nestedin the Harney Basin during the period 1982- 1986 becauseof unprecedentedhigh water levels)and, potentially,low- ered water tables resulting from geothermaldevelopment. Additionally, cattle may disturb nestingareas or destroynests; cattle were presentin many of the areas we visited. In our view, there is a need to look more intensivelyat parts of the westernGreat Basin Snowy Plover population, especially with respect to long-term stability of numbers and factors affectingreproductive success. The possibilityof enhancingthat success, especiallyon areaswhere water levelsare manipulated,seems well worth investigating.

ACKNOWLEDGMENTS

Many personscontributed to the successof our study. Among thosewho were generous with their knowledge,logistic support, and hospitalityare J. R. Alcorn, E. Alstadt, P. Carter, J. Cornely, S. Denney, L. Ditto, B. Ehlers, D. and N. Ferguson,A. Gerity, F. Grogan, R. Huxley, T. Johnson,R. Johnstone,M. Kaschke,M. LeFever, C. D. Littlefield, J. Mazzoni, V. Mills, G. Page, N. Saake,J. Scoville,G. Sheeter,L. Stenzel,T. Stierhoff, S. Thompson, D. Toweill, and R. Youst.Thirteen studentsin the 1980 EvergreenState College ornithology classassisted in the Harney Lake censuses.N. E. Herman drafted the distributionmap. To all we extendour sincerethanks. The manuscriptwas improvedby commentsfrom E. H. Burtt, Jr., D. M. Forsythe,W. D. Graul, andJ. A. Jackson.This researchwas supported Vol.59, No. I Distributionand Abundance ofSnowy Plovers [21 by U.Sß Fish and Wildlife ServiceContract No. 14-16-0001-80061. This is contribution No. 1 of Malheur Bird Observatory.

LITERATURE CITED

ALCORN,J. R. 1942. Birds affected by botulism at Soda Lake, Nevada. Condor 44: 80-81. 1946. The birds of Lahontan Valley, Nevada. Condor 48:129-138. ARmB,R. 1971.Announcing theBlue List: an "early warning system" forbirds. Am. Birds 25:948-949. EVENDEN, F. G. 1952. Additional bird records for Nevada. Condor 54:174. LINSD^LE,J. M. 1936. The birds of Nevada. Pacific CoastAvifauna No. 23.

ß 1951. A list of the birds of Nevada. Condor 53:228-249. M^RSH^LL, D. B. 1951. New bird records for western Nevada. Condor 53:'157-158. ß 1969. Endangeredplants and animals of Oregon: III. Birds. Spec. Rep. 278. Agric. Exp. Stn., Oregon State Univ., Corvallis, Oregon. --, ANDJ. R. ALCORN. 1952. Additional Nevada bird records.Condor 54:320-321. PAGE,G. W., L. E. STENZEL,D. W. WINKLER,AND C. W. SWARTH.1983. Spacingout at Mono Lake: breedingsuccess, nest density, and predationin the SnowyPlover. Auk 100:13-24. R^MSE¾,F. L. 1978. Birding Oregon.Audubon Soc. of Corvallis,Corvallis, Oregon. Received24 Oct. 1986; accepted22 Jul. 1987.