The Auk 110(1):9-20, 1993 SPECIATION IN GOLDEN-PLOVERS, PLUVIALIS DOMINICA AND P. FULVA: EVIDENCE FROM THE BREEDING GROUNDS PETERG. CONNORS,• BRIAN J. MCCAFFERY,2 AND JOHN L. MARON• •Universityof California,Davis, Bodega Marine Laboratory, P.O. Box247, BodegaBay, California 94923, USA; and 2YukonDelta NationalWildlife Refuge, P.O. Box346, Bethel,Alaska 99559, USA ABSTRACT.Two forms of golden-plover have long been consideredsubspecies, Pluvialis dominicadominica and P. d. fulva. Prior studies have shown differencesbetween forms in breedingdistributions, wintering distributions,plumage, morphology, molt, and maturation schedules.We report clear and consistentdifferences in breedingvocalizations and nesting habitat, and strict assortativemating in areas of sympatry in western Alaska. These results indicate a greater degree of differentiation between the forms than was previously appre- ciated. They are appropriately treated as separatespecies and should be referred to under the namesPluvialis dominica, for the AmericanGolden-Plover, and Pluvialis fulva, for the Pacific Golden-Plover.Received 24 May 1991,accepted 18 February1992. Two FORMSof golden-plover traditionally showing assortativemating in regionsof sym- have been treated as subspecies,Pluvialis dom- patry and clear differencesin molecular genet- inicadominica and P. d. fulva (e.g. Peters 1934, ics, plumage and morphology, biogeography, Bock1958, Vaurie 1964,Mayr and Short 1970, display behavior and vocalizations,and ecolo- AOU 1983). The form dominicabreeds on arctic gy. In practice, decisions often must be based and subarctic tundra from Baffin Island in Can- on a subset of these data. Differences between ada west to westernAlaska; fulva breedsfrom the dominicaand fulva forms of golden-plover the Yamal Peninsula in Siberia eastward to have alreadybeen documentedwith respectto western Alaska (AOU 1983). However, based plumage and morphology(Connors 1983), mi- on an analysisof almost 400 museumspeci- gration routesand wintering areas(AOU 1983), mens, Connors (1983) concluded that there was and molt and maturation schedules (Strese- no evidenceof interbreeding in western Alaska mann and Stresemann1966, Kinsky and Yald- where both forms had been collectedduring wyn 1981,Johnson and Johnson1983, Johnson the breedingseason. Employing a multivariate 1985). We now provide additional evidence statisticalanalysis to characterizespecimens, he documentingextensive breeding sympatry in detectedno increasein intermediate pheno- western Alaska, consistent habitat differences, typeswithin the regionof potentialsympatry species-specificbreeding vocalizations,and as- from Nunivak Island to Point Barrow, and he sortativemating in the two forms.These data, recommendedfull speciesstatus for the forms. bolsteredby moleculargenetic evidenceto be The museumdata, however,could not prove presented elsewhere (F. B. Gill, P. G. Connors, widespreadbreeding sympatry of dominicaand J. L. Maron in prep.), unambiguously indicate fulva,because of the absenceof breedinginfor- that separatespecies status is appropriate for mationaccompanying most museum specimens Pluvialisdominica and Pluvialisfulva. and the possibilityof distributionalchanges during the centuryof collections.Furthermore, STUDY AREA AND METHODS data identifying any potential differences in ecology, breeding behavior, or vocalizations Our observationsand data were collectedat many were not available. The AOU (1983), therefore, sites on the Seward Peninsula and Yukon Delta Na- has retained subspecificstatus for theseforms, tional Wildlife Refuge (YDNWR) in northwestern although other authorities now considerthem Alaska from 1985 through 1990 (Fig. 1). In 1988 (31 May-21 June),Connors and Maron surveyedslopes separatespecies (BOU RecordsCommittee 1986, and ridgesat many siteson the southernSeward Pen- Hayman et al. 1986). insula accessiblealong the gravel highway system Ideally, taxonomic decisions to separate emanating from Nome. The three principal roads-- closelyrelated forms should be supportedby a to Teller, Kougerok, and Council--cover more than broad spectrum of evidence, including data 300 km, repeatedlypassing through or near suitable 10 CONNORS,MCCAFFERY, ANDMARON [Auk,Vol. 110 or groups identified as present in a quadrat (i.e. Loise- leuriaprocurnbens, Ernpetrurn nigrurn, Betula nana, Ledurn palustre,Vacciniurn spp., moss,lichen, and sedge).Data from 16 quadrats were averaged for each nest. We measuredelevation change from the nestto each15-m transect point with a sighting level, totalling these for an index of slope. We measuredelevation at the nest with an altimeter and plotted nest locations on topographic maps.Using the statisticalcomputer pro- gram SYSTAT (Wilkinson 1988), we entered these data (vegetation cover, vegetation height, vegetation richness,slope, elevation) in a discriminant-function analysisto separatethe two populationsstatistically. During both 1988 and 1989 we recorded golden- plover vocalizationswith a Sony WM-D6C cassette recorder and an Audio-Technica AT815a directional microphone on TDK MA metallic tapes. Sonagrams were produced on a Kay ElemetricsModel 7800 dig- ital sonagraphusing the wide-band filter. On YDNWR, McCafiery observedbreeding golden- Fig. 1. Map of Seward Peninsula and Yukon Delta plovers at the following locations(see Fig. 1): Bethel NationalWildlife Refuge(YDNWR) studyareas. Prin- (April-May 1987), Nelson Island (May-June 1985), cipal study sitesdenoted by circles. AndreafskyHills and vicinity (June 1985,May-June 1986,May-July 1987),Ingakslugwat Hills (June1988), golden-plover breeding habitat. We selected three Pikmiktalik River headwaters (June 1985), and Cur- principal study sitesnear: Nugget Creek, mile 31 on lew Lake (April-July 1988-1990).In late May and the Nome-Kougerok Road (64ø54'N, 165ø14'W);Hor- early June 1987,McCafiery, Connors, and SarahGrif- ton Creek, mile 58 on the Nome-Council Road fin observedbreeding golden-ploversat siteseast of (64ø44'N, 164ø01'W); and Feather River, mile 37 on Curlew Lake. In addition, golden-ploverswere ob- the Nome-Teller Road (64ø51'N, 166ø05'W;Fig. 1). served by YDNWR personnel at several sites in the Other sites mentioned by name are: Cripple River, Andreafsky River watershed(June 1988, May-June mile 19 on the Nome-Teller Road; and Crete Creek, 1989). on the road to Woolley Lagoon from mile 38 of the Nome-Teller Road. RESULTS In 1989 we attemptedto revisit the three principal study sites earlier in the season(22 May-13 June). Of areas surveyed to date, we have located However, that spring had exceptionallyheavy snow- large numbers of both forms on breeding ter- fall and late snowmelt. Highwaycrews were delayed ritories only on the Seward Peninsula. Seward in opening highwaysbecause of the extensivedrifted Peninsula sites, therefore, hav• presented the snow and the need to repair subsequentwashouts most useful and revealing comparisons, and during the snow melt. We were able to reach only provide the data we emphasize here. Obser- one principal study site, Feather River, before leaving the area on 13 June. Most 1989 observations, there- vations from other sites are presentedmainly fore, occurredat a variety of locationswithin 30 km as comparisonswith the Seward Peninsula sit- uation. of Nome. We spent three to six days at each of the principal Identification.--With practice in the field, we study sitesin 1988, locating golden-plover pairs and found that both sexesoffulva and dominicawere nests,characterizing nest habitats, and recording vo- easierto identify on the basisof breeding-plum- calizations. We sampled vegetation characteristicsat age differencesthan indicated in previous re- each nest within a 50 cm x 50 cm square quadrat ports (Conover 1945, Gabrielson and Lincoln placed at four points along each of four transects,for 1959), or by examinationof museumspecimens a total of 16 quadrat points per nest. Transectswere (Connors 1983). Most males in breeding plum- set by compass,running in the four principal direc- age are easily separableby the pattern of white tions from the nest. Quadrat samplingpoints were at on the undersides. In dominica,white at the fore- 2.5 m, 5 m, 10 m, and 15 m from the nest on each transect. We recorded: vegetative cover (as estimated head and sidesof the face continuesonly as far percent of total quadrat area); maximum vegetation asthe upper breast,where it terminates,usually height within the quadrat; and vegetation richness, in a widened, bulbouspatch on eachside of the as indicated by the number of the eight plant species breast. Flanks and undertail coverts are black, January1993] Speciationin Golden-Plovers FEATHER RIVER NUGGET CREEK HORTON CREEK Fig. 2. Golden-ploverbreeding distributions at SewardPeninsula study sites. Map dimensionsare 3.6 km x 3.6 km (F = fulva;D = dominica).Circles are schematic,and do not indicateterritory-boundary locations; circle diameter is 350 m. Dark circle centers indicate nest locations.Open circles indicate areas of nesting activity with probablenests. Location of gravel road at eachsite shown as a bold line. Peripheralareas of each site map were not searched. rarely with some white mixed in undertail co- Peninsula study sites (n = 165 in 1988, n = 140 verts. In fulva, the white shows little or no in 1989). Additional differences in color, size, broadening at the upper breast, and almost al- and distribution of spots on wings and mantle ways continues in an irregular streak past the may assist in identification of both sexes in breastand along the flanks to the undertail