Field Identification of Smaller Sandpipers Within the Genus <I

IDENTIFICATION Field identification of smaller sandpipers within the genus C/dr/s Richard R. Veit and Lars Jonsson Paintings and line drawings by Lars Jonsson INTRODUCTION the hand, we recommend that the reader threeNearctic species, the Semipalmated refer to the speciesaccounts of Prateret Sandpiper(C. pusilia), the Western HESMALL Calidris sandpipers, affec- al. (1977) or Cramp and Simmons Sandpiper(C. mauri)and the Least Sand- tionately referred to as "peeps" in (1983). Our conclusionsin thispaper are piper (C. minutilla), and four Palearctic North America, and as"stints" in Britain, basedupon our own extensive field expe- species,the primarily western Little Stint haveprovided notoriously thorny identi- rience, which, betweenus, includesfirst- (C. minuta), the easternRufous-necked fication problemsfor many years. The handfamiliarity with all sevenspecies. Stint (C. ruficollis), the easternLong- first comprehensiveefforts to elucidate We also examined specimensin the toed Stint (C. subminuta)and the wide- the picturewere two paperspublished in AmericanMuseum of Natural History, spread Temminck's Stint (C. tem- Brtttsh Birds (Wallace 1974, 1979) in MuseumOf ComparativeZoology, Los minckii).Four of thesespecies, pusilla, Much the problemwas approachedfrom Angeles County Museum, San Diego mauri, minuta and ruficollis, breed on the Britishperspective of distinguishing Natural History Museum, Louisiana arctictundra and are found during migra- vagrant Nearctic or eastern Palearctic State UniversityMuseum of Zoology, tion in flocksof up to thousandsof indi- speciesamongst groups of migrantLittle BritishMuseum (Natural History), and viduals on extensive tidal flats. Two oth- Sums(Calidris minuta). A secondmajor theMuseum of NaturalHistory in Stock- ers, minutilla and subminuta, breed contributionto the identificationof spe- holm, studied numerousphotographs, farthersouth, in marshyareas of the bor- ciesin this group(and to the identifica- anddiscussed many points with individ- eal andsub-arctic zones, and, during mi- tion of shorebirdsin general) was the uals,who, through their travels, had spe- gration,are usuallyless gregarious and publicationof A Guideto theAgeing and cial familiaritywith oneor anotherplum- prefergrassy marshes and flooded fields Identificationof Holarctic Wadersby age that we lacked. for foraging.The seventhspecies, tem- Prater et al., in 1977. The detailed de- Becausemost of our field experience minckii, is primarily an arctic and sub- scriptionsof shorebirdplumages and hasbeen in easternNorth America (Veit) arcticbreeder but is rathersolitary dunng molt contained in that work are indis- and westernEurope (Jonsson), a biased migration,when it is most often found pensableto the shorebirdenthusiast and perspectiveon the comparativeappear- aroundfreshwater pools and in grassy arealso particularly useful for thecorrect ance of each of these birds has been in- marshes. identification of small calidridines in the evitable. Therefore, the identification Amongshorebirds, the specieswithin hand. A new paper in British Birds pointsdiscussed in this papertend to re- thisgroup are probably the mostdifficult (Grant 1984), has used the samepaint- flect comparisonswith the common to identify.When in breedingplumage, ingsby Jonssonthat appearhere. North Americanspecies. Such a bias, we the species-specificcolor patterns are Our approachis to define and summa- have assumed,is largely sharedby the rather obvious, and render identification nze thosecharacters by whichpeep sand- readers of American Birds. straightforward.But at other seasons, pipersmay be distinguishedfrom onean- thesespecies are extremely similar to one other in the field. We have avoided SPECIES TREATMENT anotherand usuallyrequire considerable detailed discussions of characters that previousexperience, exceptional view- wouldbe of usein thehand, both to keep ing conditions,and a healthyamount of thetext within a manageablelength, and ECOVER theidentification ofseven patienceto identifycorrectly. In the fol- also becausewe lack extensiveexperi- Holarcticspecies in the genusCa- lowingsections, we identifythose mor- ence with live birds in the hand. For iden- lidris that are collectivelycharacterized phologicalfeatures most critical to the tificationof specimensor of live birdsin by their very small size. These include properidentification of thesespecies. Volume 38, Number 5 853 TOPOGRAPHY (Figure 1) way up the crown. The "forecrown"re- tion"is thedistance between the tip of the fers to the featherinnimmediately above longestprimary and the tip of the longest N OURdescriptions of plumages and the base of the bill. tertial. molts, we follow the terminologyof Upperparts:The "V" marksare whitish Humphreyand Parkes (1959), further stripeson theback of somepeeps that are SIZE discussedas it appliesto shorebirdsby derivedfrom white fringesto the mantle Palmer (1967). feathers,scapulars, or both. Depending LTHOUGHTHErange in sizebetween In discussionsof peepidentification, it on how thesefeathers are lying, the "V" the largest species(Western Sand- is convenientto speakof certaingroups marksmay appearsharp or diffuse.We piper)and the smallest(Least Sandpiper) of feathersthat are similarly coloredor refer to "mantle" or "scapular.... V" is substantial, size differences between patterned,but which are not ordinarily marks,depending on which feathersare otherspecies are smalland usuallydiffi- referred to under a collective term. For involved. cult to judge. The sandpipersin this example,of the five rowsof scapularson Underparts:The "breastsides" include groupare sexuallydimorphic in size (fe- peeps,the upper three rows are often col- the featherinnabove the flanks, or just malesslightly larger), and the apparent ored differently from the lower two. aheadof andabove the bendof the wing. size of an individualbird can vary ac- Therefore,we speakof the "upper"and Wings:On peeps,the middleand greater cordingto the positionof its feathersand "lower" scapulars(Fig. 1). Some other secondarycoverts are frequentlyvisible to otherspecies with whichit is associat- instancesof terminologypeculiar to this on a standingbird, andtheir coloration is ed. Minor differences in the distance be- text are as follows: frequentlycritical in the identificationof tween birds, which to the observer are Head: The "lateral crownstripes"are somespecies. For convenience,we refer foreshortenedby opticalequipment, can pale, usuallywhitish, lines which paral- to theseas simply "greatercoverts" or resultin a significantdistortion in the ap- lel the superciliumabout one-third of the "middlecoverts." The "primaryprojec- parentrelative size of birds that seemto supercilium lateralcrown stripe cro•wn / / aur!cul.ars. • • .- ..i / ninanectc . •,-,$•/•.•/• "V"mark jorecrown•f• •' .'/• / •ntle lores• '•:•" • • •- • • upperscapulars cutmen•. _• .-•T'.•:" .... : lowerscapulars chin• • •' .f • •' ' •:• .• • projection upperbreasf :•' '• '• ' ' • ' "• ' ' undertail coverts lowerbreas,•lesser coPerrs Pe•l fianks••• • xmedian covertsgreater coverts bel• • t • • •FS•S i•r toe • midd•outer toet• •• • hindtoe Figure 1. Topographyof a Calidris. 854 AmericanBirds, September-October1984 be standingnext to oneanother. There- Westernsandpipers. One shouldbeware Little stints,by comparison,have finely forethe proportions, rather than the size of birdsthat lack webbingbut acquirea tippedbills. perse, are more useful in determining the "club-footed" look as a result of mud The extent of the folded primary tips species. caked to their toes. beyondthe tip of thelongest tertial seems The shapeof the bill, while it varies to be of some use in the field, but vari- with sex, age, and in somecases, geo- ation in this feature has not been thor- STRUCTURE AND POSTURE graphical origin, is a species-specific oughlyinvestigated. The LeastSandpip- character and is often the first clue to the er and Long-toedand Temminck's stints NMANY cases, identification ofpeeps presenceof a rare species.Critical as- have very little, if any, primary projec- dependsupon structural characters of pects include the overall length, the tion. Of the black-leggedspecies, Little thebill, legsand feet (Fig. 2). Two North amountof curvature,and the degreeof and Rufous-neckedstints usually have Americanspecies, pusilia and mauri, pointednessas observed both from above greaterprimary projection than Semipal- havepartial webbing between the toes, and from the side. Lateral expansionof mated and Western sandpipers.This whichthe similarPalearctic species, min- the bill tip, resultingin a slightlyspatu- charactershould probably be usedonly uta and ruffco!Ils,lack. This featureis late condition,is typicalof the Semipal- forjuveniles in fall, asone cannot assume surprisinglyeasy to see,once one is fa- matedSandpiper but is only visible when thatthe primariesare completelygrown miliar with the differencein appearance the bird is viewed head-on. A blunt- in birdsof other ages. between webbed and unwebbed feet tippedprofile, onlyvisible from the side, The shapeof the body and the stance (Fig. 3). North Americanobservers can is characteristicof the Semipalmated typicallyassumed both lend a greatdeal usefullystudy this distinction by compar- Sandpiperand Rufous-necked Stint. The to the appearanceof a sandpiperand ing the feet of Leastrs. Semipalmated/ Least Sandpiperand the Long-toedand thereforeprovide useful clues to its iden- Figure2. Typicalsilhouettes of four black-leggedpeeps. Little Stint(top left) and Rufous-necked Stint(top right) in first alternateplumage; Western

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