THE PRACTICED EYE Kenn Kaufman photographs from VIREO CurlewSandpiper and its I.D. Contenders FTERTHE FOURTH OFJULY, AS BIRD- is almostannual in migrationat several adultsprecede the juveniles on the trek songin thewoods declines, many spotson our Atlantic Coast.Already it south. In September and October, birders head for the shore--or for has been recorded in more than half of whenthe specieswould be represented the reservoirs or flooded fields or our statesand provinces,and I predict by juveniles or by adults in winter sewageponds, or anywherethat mi- that eventuallyit will visit all the rest. plumage,the Curlew Sandpiperwould grant shorebirdsmight touch down. Still, it is never routine, and it causes be more difficult to detect. This Prac- The southbound migration of the excitementwhenever it appears. ticed Eye looks at these more subtle shorebirdsis a prolongedevent, lasting July to early August is the time plumagesof the Curlew. from late June to December, and it when most southbound Curlew Sand- The comparisonmost often made is holdsendless potential for excitement. pipersare found.But is that whenmost to the Dunlin (Calidris alpina). Both Rare stray wadersfrom anywherein actually occur here? Not necessarily. the Dunlin and the Curlew Sandpiper the northernhemisphere can (and do) Mid-summer is when the adults pass (like a great many other shorebirds) drop in almost anywhere in North through,still wearingalternate (breed- are mostly grayish above and whitish America. ing) plumage, a rich chestnut that belowin non-breedingplumages. Both One of the most frequentand wide- stands out like a beacon on a mudflat are among the larger species of spread of the strays is the Curlew crowded with drabber peeps. These Calidris, the genusof the "peeps"and Sandpiper(Calidrisferruginea). It has bright Curlews are hard to overlook. "stints." Both have bills that are more nested(rarely) in arcticAlaska, and it But as in mostother shorebirdspecies, or lessdecurved. The potentialfor con- The Curlew Sandpiper breeds mainly in the high Arctic of the JuvenileCurlew Sandpiper in fairly freshplumage (early Septem- Soviet Union, and performs extensivemigrations. Photographed ber). The edgings on the scapulars are buffy-white, a slightly in late winter in New Zealand, this adult showsseveral of thefieM warmer buff on the upper scapulars,but wtth much less contrast marks of the speciesto good advantage: the decurvedbill, the than on afresh juvenile Dunlin; noticethe dark subterminallines whitewing stripe,the white rump,and the lengthof the legs.This on the covertsand lower scapulars.By this season,the buff wash bird is molting into breedingplumage, developingthe bright on the chestand face hasalready begunto fade. Thepale supercil- chestnutcolor that will makeit so conspicuousin springand sum- ium is quite apparent on this bird. Photograph/R. J. Chandler/ mer.Photograph/Brian Chudl eigh /VIREO (c20/1/135) VIREO (c18/2/071) Volume 44, Number 2 189 fusionis automaticallypresent. Bill shapeis routinelymentioned as a major field mark for separatingthese two. In general, the bill of Curlew Sandpiper is evenly decurved, while that of Dunlin tendsto be straighterat the baseand droopedat the tip. How- ever, bill shapein both speciesvaries enoughthat some individualsof either may look intermediate,at leastsuperfi- cially. Another well-known difference is that Curlew Sandpiperhas a white rump while Dunlin does not. This is usuallyimpossible to seeexcept when the bird flies--and most birders would JuvenileCurlew Sandpiper in late September.Although the plumage has begunto fade rathernot flush a potentialrarity, lestit and wear slightly,molt is not yet underway, so the upperpartsstdl havea neatlyscaled might fly away for good! look.The upperpartsare all brownand bullY-white,showing far lesscontrast than would In shape,Curlew Sandpiperlooks a be apparenton juvenileDunlin or Stilt Sandpiper.Notice that the superciliumis much strongerthan on Dunlin. Photograph/R.J. Chandler/VIREO(ci8/I/033) bit more slim and elongatedthan the Dunlin, with a longer neck when standingerect. But this distinctiondis- appears when the Curlew hunches down--and fluffing out its body feath- ers can even obscure the fact that its legs are longer. Thus silhouettealone wouldbe a very tricky field mark. Dunlinsin full juvenal plumageare very distinctive,but the averageNorth American birder seldom sees such birds. Most young Dunlins have alreadybegun to molt by the time they show up at migration stopovers.This in itself is a good distinction from C u' •4• ':Scit tn w•nter young Curlew Sandpipers,which are t ntarily shows't whtte upp•- generally still in complete juvenal tail coverts.The su cili• i•rt plumage by mid-autumn. (Curlew tt•tinct•Notice bdl sha d Sandpipersmay put off the molt until eft length. Ph ta t t/B an later becausethey havefarther to go in migration:most of them winter nearor southof the Equator,while mostDun- lins winter well north of it.) See the accompanyingphotos and captionsfor comparisonsof young Curlews and Dunlins. Curlew Sandpiper in full winter (basic)plumage is much lesslikely to be seen on this continent, and it would have to be identified with care. Com- paredto winter Dunlin, it would show a more distinct pale supercilium, a generally whiter chest, and slightly paler upperparts.Bill shape,rump pat- tern, and leg length would all have to be notedcarefully. Under some circumstances, the juvenile Stilt Sandpiper (Calidris himantopus)has also been misidenti- fied as a Curlew Sandpiper.Although CurlewSandpiper in winter,feeding. In this hunched-overposture the bird suggeststhe chunkiershape of a Dunlin,and it is turnedso that thepale superciliumand chest are not the Stilt's legs are distinctly longer obvious.However, the dark terminalcrescents still visibleon someof the covertsand (and usually yellow), this may not be scapularsindicate that the'birdis not a Dunlin, and suggestthat it is a first-winterCurlew apparentwhen the bird is wading(as it (showingthe worn remainsof juvenalplumage). Photograph/Brian Churlleigh/VIREO oftenis). The adultStilt Sandpiperhas (c20/1/136) 190 AmericanBirds, Summer 1990 a long, droop-tipped bill, but on a young bird in its first southward migrationthis may not be fully devel- Dunlin in fresh juvenal plumage, oped yet: its bill may look almost with lots of contrast on the evenly decurved. Since this species scapulars,with rich buff on the face and neck,and with smeary also has a white rump and a distinct black spots extendingdown the supercilium, it can mislead some breast and sides and onto the observers--especiallythose who are flanks. North Americanpopula- looking a little too hard for Curlew tions of Dunlins are generally Sandpipers.The best defense against not early migrants, and young this error is to slow down and look Dunlins are hard tofind at lower latitudes before September;this carefully at leg color and length, head juvenile was located in late shape,neck length, and the exact pat- summer in northern Alaska. tern of the scapulars.For practiced Photograph/J.P. Myers/VIREO eyes, the shapeof the bird will auto- (m01/6/020) matically provide a clue that some- thing is amiss...allowingthe observer to appreciatethe subtletyof the Stilt Sandpiperand then move on, knowing that the real Curlew Sandpipermay be not far away. ß No longer in full juvenal plumage, this young Dunlin (pho- tographedin early Septemberin New York) has already begun moltingin grayfeathers on thescapulars and back,and it is losing the black mottling on the sides and flanks. Most young Dunlins alreadylook like this by the time they appearsouth of the Arctic'. Photograph/ThomasH. Davis, Jr/VIREO (d03/3/025) Portrait of a winter Dun- lin. The head is mostly gray, with no obvious supercilium,and thereis a gray wash across the chest.In somepopulations (including some that occur in western North America) the fine streak- ing on the sidesand flanks is eitherfainter or lacking. Photograph/Robert Vil- lani/V1REO (v05/2/080) Volume44, Number2 191 iper in veryfresh juvenal plumage. The bill is not to its full adult shape.At this point, while the still veryfresh, the bird is separatedfrom juve- Sandpiperby the colorfulscapulars -- with the ulars edgedrich chestnut,the lower ones black- lite edges.Juvenile Curlew Sandpiperhas gray- Mars with buff edgeswhen it is fresh. After the gins to becomeworn, however,the two species ch othermore closely. Photograph/Arthur Mor- (ml 7/13/147) YoungStilt Sandpiperin mid-autumn,having molted the colorful upper scapulars.It still has blackishcoverts with obviouswhite edges,showing a little more contrast than a Curlew Sandpiper wouldat that season.The bill, probablynot quitefull-grown yet. could be misinterpretedas showingthe samecurved shape as that of Curlew Sandpiper.However, other aspectsof shapeare wrong for that species:the neck is too long, the body looksa little too elongated,and theforehead lookstoo sloping(not steepenough) for Curlew Sandpiper. Photograph/Serge Lafrance/VIREO (106/4/102) Onfurther reflection,if you don't want to work on discerningthese bb'dsin subtleplumages, get out in mid-summerand lookfor adult Curlew Sandpipersbefore they molt out of their bright breeding garb. This individualwas actuallyphotographed in early spring, still showing white edgings on the feathers of the underparts, whichwill disappearwith wear.The pattern on the upperpartswill also be less striking on summerbirds. But the overall chestnut color will make a mid-summerCurlew Sandpipervery conspicu- ous -- even when it is asleep_Photograph/Brian Chudleigh/ VIREO (c20/1/138) VIREO (Visual Resources for Ornithology),at the Academyof Nat- ural Sciencesof Philadelphia,is the world's first and foremost scientific collectionof bird photographs.Estab- lished in 1979, the collection now holdswell over 100,000 images,rep- resenting about half of the world's bird species.For more background, see the feature on VIREO by J.P. Myers et al. in AmericanBirds Vol- ume38, Number3, May-June1984. 192 American Birds, Summer 1990 .