-

28

Field identificationof forDts of

Lesser Golden-PloverRecently Connors (1983) argued that the two racesof Lesser Golden-Plover Pluvialis dominica areactually full species. This argument has beenaccepted by Hayman et a1.(1986) and reportedly bythe British Ornithologists' Union. The AmericanOrnithologists' Union (1983, 1984, 1985) has notaccepted this proposed split.Connors was able to separate 96% of breeding-plumaged specimens, using a discriminant functionanalysis of measurements. The percentage ofintermediate birds was the same in areas far from thezone of contact as it was in areas close to this zone.

Connors was unable to detect a cline of intergradesor a hybrid zone, and he concluded that the two taxamust be reproductively isolated through assortativemating.Connors proposed the English name "AmericanGolden-Plover" for the North American formdominica and "Pacific Golden-Plover" for the

Asiatic and Pacific form fulva. This arrangement isfollowed by Hayman et a1.In this paper we use thenames fulva and dominica to designate these taxawithout taking a position on their actual taxonomiclevel. For an argument against the proposed split,see DeBenedictis (1984).

Breeding RangeDominica breeds in North America from the BeringSea across northern Alaska and Canada east toBaffin Island. As late as 1900 it was an uncommonbreeder in the Anadyr Range and in the ChukchiPeninsula in extreme northeast Siberia, but it was

- extremely rare west of the Bering Straits by 1939,when Portenko (1981) found a nesting pair onWrangel Island.Fulva breeds in Alaska along the Bering sea and upthe northwest coast to Point Barrow, on theChukchi Peninsula south to the Gulf of Anadyr, andalong the Arctic coast of Siberia west to the Yama1Peninsula and south to the tree line (Portenko 1981).

Winter RangeDominica winters entirely in South America, from

J. L. Dunn,J. Morlan,

andC. P. Wilds

~

Bolivia, Paraguay and southern Brazil south tonorthern Argentina and (rarely and irregularly)northern Chile (Blake 1977).There are no definitewinter records of dominica in North America; aspecimenfromTexasinJanuary(Oberholser1974)requires confirmation.Fulva winters in eastern Africa south to Tanzania(especiallyin Ethiopia and Somalia); in very smallnumbers from Israel to Oman; around the Indiansubcontinent to southeast Asia, southern China,Indonesia, Australia, and New Zealand; andthroughout the Pacific from the Philippines toHawaii and the Tuamotu islands (AmericanOrnithologists' Union 1983,Cramp and Simmons1983).It alsowintersregularlyin smallnumbersin afew locations in coastal California.

MigrationDominicas southbound migration route is mainlyacross Canada to northern Ontario, then over theAtlantic to the LesserAntilles and northern SouthAmerica. It is an uncommon transient along theNorth Americaneast coast fromNewfoundlandandNova Scotia to North Carolina, but is rarelyreported farther south. Some juveniles follow aroute south through central North America.In spring almost all birds travel through interiorSouth America,up CentralAmerica,and acrosstheGulf of Mexico, making landfall in the Gulf states.Final passage is primarily up the MississippiandMissouri valleys and across the Canadian prairieprovincesto the breedinggrounds.Fulvas migrations are more diffuse, in apparentlydirect flightsacrossthe Pacificand Siberia.In NorthAmerica, it is an uncommonmigrantdown thewestcoast.

VagrancyDominica is a rare migrant along. the NorthAmerican west coast, mostly in autumn, and alongthe east coast in spring. It is almost annual inautumn as a vagrant to the British Isles andcontinental Europe. There are severalsight recordsfrom west and northwest Africa (Urban et a1.1986),

29

and it has been reported both from Australia andNew Zealand.In North America outside Alaska fulva is extremelyrare except along the west coast. It has strayed toAlberta, Idaho, Maine and Greenland. It has alsobeen recorded in the Galapagos Islands and Chile.Fulva is a casual vagrant to Scandinavia and westernEurope, including the British Isles, where dominicapredominates, and to southeastern Africa as farsouth as Capetown.

HabitatObservations by JLD near Nome, Alaska, indicatethat fulva breeds on tundra and marsh edges alongthe coast and river valleys, while dominica occurs onwell-drained mountain slopes. Connors, however,found no significant habitat differences, with bothforms nesting on well-drained tundra and mountainslopes. Further studies on the breeding grounds areneeded to clarify possible habitat selection there. Inmigration both forms occur together on grazedpastures in California.

Field SeparationStructure: The best character is the number of

exposed primaries past the folded tertials. Dominicahas a longer primary projection, with four or fiveclearly exposed primary tips. Fulva has a shorterprimary projection, with only three exposed primarytips on the folded wing. On both forms the outer twoprimaries are nearly equal; thus, very Closeviews orsharp photographs may be necessary to establish thedifference. We do not advocate using this distinctionon molting birds that are missing tertials orprimaries or on worn birds on which heavilyabraded tertials may reveal an additional primary.Nevertheless, on freshly molted birds in equivocal orintermediate plumages primary projection may bethe best single field character.Fulva averages smaller and slimmer than dominicabut has a proportionally longer bill and slightlylonger legs. These differences are difficult to use withprecision, although they may be useful aspreliminary clues.

Breeding plumage: The best character in breedingmales is the pattern of the underparts. Fulva has asmall white patch on each side of the breastcontinuing as a line down the flank, and theundertail-coverts are largely white, recalling GreaterGolden-Plover P. apricaria. Breeding maledominica has larger, bulging patches on the sides ofthe breast often nearly meeting across the front;otherwise the underparts are entirely black.

In breeding females, plumage differences are muchless evident, but dominica still shows bulging whitepatches on the sides of the breast in the same shapeas on breeding m/ales. This pattern is much lessclearly defined, however, because the entire blackarea on the underparts is variably flecked with white.Female ful-vaoften have the underparts largely whitewith very little black, mostly confined to the belly.In both sexes fulva differs from dominica in having,on average, a narrower black band across theforehead, so that the white nearly meets the base ofthe culmen. (The mean difference, however, isO.9mm, and the measurements overlapsubstantially, making this a field character ofdubious usefulness). The width of the white bandacross the forehead is highly variable, and shouldnot be used as a reliable difference between the twoforms.

Fulva often appears brighter above, the gold andwhite spots on the upperparts averaging larger andbrighter, while on dominica the gold and white spotsare smaller, resulting in a generally darker overallcoloration. There appears to be some difference inthe amount of contrast between the mantle and the

wings in the two forms. On fulva the predominantlygold-spotted mantle often contrasts with thepredominantly white-spotted wings. On dominicathe mantle tends to be less spotted with gold and thewings more gold-spotted, resulting in a pattern withless contrast. This difference is presented here asonly a tentative observation needing furtherconfirmation.

Juvenile and winter plumages: The upperparts aremuch more yellow in fulva, again suggesting GreaterGolden-Plover. Dominica is much grayer (except onthe rump) recalling Black -bellied (Grey) Plover P.squatarola.In fulva the entire facial area is usually suffused withyellow. In dominica yellow is usually absent on theface or confined to a slight wash on the supercilium.Dominica has a solid dark area of variable widthfrom just in front of the eye through the ear-coverts.Fulva has a pale area immediately around the eye,and the ear-coverts tend to form a distinct post-ocular spot separated from the eye.On fulva the nape is paler, less streaked, and muchyellower than on dominica. The cap and mantle ofdominica are darker with smaller gold spots, givingit a better-defined cap and darker area on the upperback. Dominica usually lacks yellow on the napeexcept for a small amount near the top onindividuals with a yellow-tinged supercilium.

Pluvia/is dominica fulvaJuveniles (Note less dark around face,the bright gold upperparts including the wingcoverts, and rather short primary extension withonly three exposed primaries past the longesttertial). Photos by Ed Harper.

~

PlluvialiS dominica fulva

. Breeding male (noteproportionate1y long legs, a

. rather even whlte zone down the sldes and flanksand almost no black on the forehead).

. Photo by Pavel Tomkovitch.

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31

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-Pluvialis dominica dominica

JuvenjJe (note proportionately shorter legs thanfulva, the darker area around the eye wdh solidpatch and long primary extension: see above).Also the wing coverts are edged whitish whichcontrast slightly with the more gold spottedupperparts. Photo by Jonathan Alderfer.

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32

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Breeding plumage of dominica (note rather broadblack forehead band and broad white patches on sidesof breast). Photo by Alan Wormington.

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Juvenile dominica (note dark eye patch extendingin front of and behind eye that almost connects to post ocularspot. Also note the long primaryextension with fully four exposedprimariespast thelongest tertial).Photo byAlan Wormington.

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33

Most birds can be separated by overall color andpattern, but a substantial number of individualsshow ambiguous plumage patterns or appearintermediate. On such ]1roblem birds, werecommendusing the number of exposed primariespast the tertials, discussed above. Some birds arebest left unidentified,given the current state of ourknowledge. Caution is especially needed in sight-records of birds outside their respectiveranges.It should be noted that juvenile Black-belliedPlovers in fresh plumage may appear extensivelygold-spotted on the upperparts and buff-washedonthe breast, causing confusion with dominica. Inaddition to structural differences, the paler crownand short, ill-definedsupercilium of squatarola areusefulfield characters.

VoiceAthorough study of the vocalizationsof both formsis badly needed. Both apparently have complicatedrepertoires. A study by Urner (1933)described 20distinct calls given by migrant dominica in NewJersey. We are not aware of any differencesin thevocalizations of the two forms which are useful inidentification.

DiscussionMuch additional work needs to be done on thebreeding grounds to further clarify the taxonomicstatus of the two forms. In particular, differencesindisplay and vocalization may be critical indeterminingisolationmechanismsthat maypreventhybridizationinthe areasof contact. Thepercentageof mixed pairs and the successof hybrid offspringare currently unknown. Hybridization wouldcertainly complicate field indentification,particularly on the North American west coastwherehybrids would be most likely to occur.Additional work is also needed in fieldidentification. Many of the points we suggest hereneed further testing and corroboration in the fieldand in the museum. Other characters may bediscoveredwhichmayclarifyfieldidentificationandpossiblyshed light on the taxonomic status of thetwo forms. It is particularly important to be able todistinguish true hybrids from extreme variantswithina population. There isenoughvariation in theplumages of these forms to make confirmation ofhybridization a difficult and controversial subject.We urge that intermediate birds should not beinterpreted as hybridsuntil the variabilityof knownplumagecharacters becomesclear. We also suggestgreatcaution in identifyingany individual that does

not showthe typicalpattern of onetypeor the other,particularly in the case of out-of-range birds. Wehope that further fieldwork in western NorthAmerica may help to clarify the identification andstatus of these two forms, as this is the only areawhere both forms regularly occur together.

AcknowledgementsWe wish to thank the entire international delegationat Eilat, especially Dick Forsman, Lars Svensson,and Per Alstrom. Lars Jonsson, Dennis Paulson,and Rich Stallcup provided helpful comments forwhich we are grateful

ReferencesAMERICAN ORNITHOLOGISTS' UNION.1983. Check-listof North American Birds, 6th ed.Washington.AMERICAN ORNITHOLOGISTS' UNION.1984. Report of the meeting of the committee onclassificationand nomenclature. Auk 10I: 348.AMERICAN ORNITHOLOGISTS' UNION.1985. Thirty-fifth supplement to the AmericanOrnithologists'Union Check-listofNorth AmericanBirds.Auk 102:680-686.BLAKE,E.R. 1977Manualof NeotropicalBirds,V01.I. Chicago.CONNORS, P.G. 1983. Taxonomy, distribution,and evolution of goldenplovers (Pluvialisdominicaand Pluvialisfulva).Auk 100:607-620.CRAMP, S., SIMMONS, K.E.L. 1983.The Birdsof the WesternPalaearctic, Vol. III. Oxford.DEBENEDICTIS, P.A. 1984.Gleanings from thetechnicalliterature.Birding16:280-282.HAYMAN, P., MARCHANT, J., PRATER, T.1986. Shorebirds: An identification guide to thewaders of the world. Boston.OBERHOLSER,H.C.1974TheBirdLifeofTexas.Austin.PORTENKO,L.A. 1981.Birds of the ChukchiPeninsula and Wrangel Island, Vol. I. New DelhiURBAN, E.K., FRY C.H., KEITH, S. 1986.TheBirds of Africa, Vol. II. London.URNER, c.A. 1933. The voice of the GoldenPlover. Auk 50:420-425.

J. L. Dunn, 4710 Dexter Drive, Apt. 7, SantaBarbara,CA 83110, u.s.A.J. Morlan, 417 Talbot Avenue, Albany, CA 94706,U.S.A.C. P. Wilds, 3331 N Street NW, Washington, DC20007, U.S.A.