THE PRACTICED EYE PectoralSandpiper and Sharp-tailed Sandpiper photographspom VIREO (Visual Resourcesfor Orntthology) at the Academyof Natural Sciencesof Philadelphia Kenn Kaufman of the derisivelynamed "peeps"and N"stints"THE GENUS and variousCALIDRIS. otherTHE difficultGENUS shorebirds, the Pectoral Sandpiper (C. melanotos)has one trait that shouldbe appreciated by strugglingbirders. It is not the largestof itsgroup, nor the most colorful, nor the most distinctive--but it does show practically no seasonal variation. Other shorebirdsmay have three utterly different plumages, de- pending on seasonor age,but Pectoral Sandpiperhardly varies.Learn the Pec- toral at one seasonand you will know it all year. Until recently,it was safeto saythat identification of Pectoral Sandpiperin- volved only one strong contender: Sharp-tailed Sandpiper (Calidris acu- minata), which is closelysimilar only in adult breeding plumage. This simple comparison was muddied somewhatby the unveiling of Cox's Sandpiper, a pesky varmint describedas recently as 1982, evidentlya long-distancemigrant that could theoretically show up any- where in the world. Cox's Sandpiperre- ceives some attention elsewhere in this issue, but the focus of this "Practiced Eye" is on Pectoral Sandpiper as it comparesto the reasonablealternative, the Sharp-tailed. One of the more northerly breeding sandpipersin the American and Sibe- rian arctic, the Pectoralwinters mainly in southern South America. On passage through North America it is most com- mon through the Great Plains, es- Adult PectoralSandpiper in summerat Barrow,Alaska. Photo: J. P Myers/VIREO (m01/99/ pecially in spring, but fall migrantsare 027). quite widespread. 1356 American Birds, Winter 1987 Sharp-tailed Sandpiper is a northern Siberian breeder, wintering mainly in Australia. In North America it appears mostly as a fall migrant or stray: some- times in good numbers in Alaska; reg- ularly, in small numbers,in British Co- lumbia and Washington;irregularly. in very small numbers, farther south on the Pacific Coast; and rarely elsewhere, includingthe Atlantic Coast. The vastmajority of the Sharp-taileds found in North America (especially outsideAlaska) are juveniles, and most appear betweenmid-September and late October.In juvenal plumagethe Sharp- tailed is quite distinctive, and often no- ticeable beeause of its rich colors: rufous or chestnut on the upperparts, and bright orange-buffon the breast. No other Calidris matches these colors, and the effect is more likely to suggesta ju- venile Ruff (Philomachus pugnax) or even the juvenile of the Pacific race of JuvenilePectoral Sandpiper. September, in New York.Photo.' Thomas H. Davis/VIREO (dO3/ Lesser Golden-Plover(Pluvialis dom- 3/023). inica.lidva). Bright coloralone is not quite enough for a safe identification of Sharp-tailed, however. Some Pectorals are brighter than others, and some fresh juvenile Pectoralshave fairly bright chestnuton the crown and back, and a buffy wash on the breast.The juvenile Sharp-tailed is also distinguishedby detailsof pat- tern, so that it would De equally iden- tifiable in a black-and-white photo- graph. Pattern of the underpartsis the most obvious difference. While Pectoral Sand- piper always has moderate to heavy streakingthat extendsdown to a sharp cutoff on the lower breast,the juvenile JuvenilePectoral Sandpiper Photo: Robert Villani/VlREO (v05/2/075). Sharp-tailed has only fine streaking acrossthe upper breast and down the sides. The lower breast on juvenile Sharp-tailed is unmarked orange-buff, shadingevenly into the white belly.Ju- venile Sharp-tailed also has a very con- spicuouspale supercilium,almost un- marked, that often seems to become broader behind the eye; the Pectoral's supercilium tends to be less conspicu- ous, more invaded by dusky streaking, and narrower behind the eye. The ap- pearance of an eye-ring is often more noticeableon Sharp-tailed. Adults in breeding plumage can De more tricky to separate.In full breeding plumage, Sharp-tailed is marked like Pectoral on the upper breast, but has a light spotted effect fading out on the lower breast,and large chevron-shaped marks extending down the sides and Close-upof adultSharp-tailed Sandpiper on winteringgrounds in Australia.Photo: S. Holohan/ flanks and onto the undertail-coverts. VIREO (h09/1/0229 Volume 41, Number 5 1357 Pectoral Sandpiper has only light streakingon the sidesand flanks, and the sharp demarcation on the lower breast is the predominant feature of its pattern. In late summer and fall, how- ever,Sharp-taileds in transitional stages can losemany of the obvious marks on the flankswhile retaining the streakson the breast, and they can look surpris- ingly similar to Pectoral at this point. Such birds should be identified with greatcaution, with closeattention to the precise pattern of the lower breast and flanks. A conspicuouseye-ring on adult Sharp-tailed may also be a good clue. Distinguishing the two species in winter will rarely be a problem here, since Pectoral Sandpiper is extremely rare in North America at that season, and Sharp4ailed is strictly accidental JuvenileSharp-tailed Sandpiper. Photo' Mark Stocku/VIREO (sl 7/1/005) then. Winter plumage in the Sharp- tailed looks like a very dull versionof its juvenal plumage, with the orange- buffof the breast replaced by dull gray- buff, and the upperparts mostly dull gray-brown. The crown may retain a hint of chestnut. Behavior and habitat choice in mi- gration seem to be similar for the two species,but the Sharp-tailedsthat I have watched have often been rather slow- moving, spendinglong periods picking deliberatelyat the mud in a small area. Differences in structure are worth noting, and can be especiallyhelpful in spotting subtle adults. Sharp-tailed Sandpiper tends to have a slightly shorterand straighterbill than Pectoral Sandpiper, and often looks flatter- headedand shorter-necked.Sharp-tailed also tends to be more rotund in silhou- ette; and although its legs average slightly longer than those of Pectoral Sandpiper.the heavy-bodiedshape may make it look a little shorter-leggedin proportion. As in so many other cases, the bestway to preparefor recognizing the rarity (Sharp-tailed) is to become thoroughly familiar with the more common species (Pectoral). The best way to become a skilled birder is to spendtime lookingcarefully at common birds. ! JuvenileSharp-tailed Sandpiper. Photo: JuvenileSharp-tailed Sandpiper.Photo: ThomasH. Davis/VIREO (d03/3/024). Peter G. Connors/VIREO (c05/1/050) 1358 American Birds, Winter 1987 .