Field Identification of Smaller Sandpipers Within the Genus <I

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) andthe LeastSand- tionatelyreferred to as "peeps" in (1983). Our conclusionsin this paperare piper (C. minutilla), and four Palearctic North America, and as "stints" in Britain, basedupon our own extensivefield expe- species,the primarilywestern Little Stint haveprovided notoriously thorny identi- rience,which, betweenus, includesfirst- (C. minuta), the easternRufous-necked ficationproblems for many years. The hand familiarity with all sevenspecies. Stint (C. ruficollis), the eastern Long- first comprehensiveefforts to elucidate We also examined specimensin the toed Stint (C. subminuta)and the wide- thepicture were 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, whichthe problem was approached from 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 British Museum (Natural History), and viduals on extensive tidal flats. Two oth- Stints(Calidris minuta). A secondmajor the Museumof Natural History in Stock- ers, minutilla and subminuta, breed contributionto the identificationof spe- holm, studied numerous photographs, farthersouth, in marshyareas of thebor- cies in this group (and to the identifica- anddiscussed many points with individ- eal and sub-arcticzones, and, duringm•- tion of shorebirdsin general) was the uals,who, throughtheir travels,had spe- gration,are usuallyless gregariousand publicationof A Guideto theAgeing and cial familiaritywith oneor anotherplum- prefergrassy marshes and flooded fields Identificationof Holarctic Waders by age that we lacked. for foraging.The seventhspecies, temo Prater et al., in 1977. The detailed de- Becausemost of our field experience minckii, is primarily an arctic and sub- scriptionsof shorebird plumages and hasbeen in easternNorth America (Veit) arcticbreeder but is rathersolitary during molt contained in that work are indis- and westernEurope (Jonsson),a biased migration,when it is mostoften found pensableto the shorebirdenthusiast and perspectiveon the comparativeappear- aroundfreshwater pools and in grassy arealso particularly useful for the correct 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 paper tend to re- thisgroup are probablythe mostdifficult (Grant 1984), has used the same paint- flect comparisonswith the common to identify. When in breedingplumage, ings by Jonssonthat appearhere. NorthAmerican species. 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 the hand, bothto keep ing conditions,and a healthyamount of the text within a manageablelength, and eCOVER the identification ofseven patienceto identifycorrectly. In the fol- also becausewe lack extensiveexperi- Holarcticspecies in the genusCa- lowing sections,we identify thosemor- 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. Patntedespecially for AmericanBirds by LarsJonsson, the opposite page shows four smallsandpipers in juvenalplumage. In thebackground, a juvenile Western Sandptper (Cahdrismaud) is flanked by twojuvenile Semipalmated Sandpipers (C. pusilia).The juvenile Western has upper scapulars with a pronouncedcontrast between the tawny frtngesand dark centers, as wellas a palefaceand "beady"eye,' both of these characters are lacking in thejuvenile Semipalmated Sandpipers. In theforeground is a juvende Rufous-neckedStint (C. ruficollis),similar to thejuvenile Western but with a shorterbill, nowebbing between the toes, and with brighter, more cinnamon/rufous upperparts Volume 41, Number 2 213 TOPOGRAPHY (Figure l) way up the crown. The "forecrown"re- tion"is the distance between the tip of tbe fersto the featberingimmediately above longestprimary and the tip of thelongest • our descriptionsof plumages and the base of the bill. tcrtial. molts, we follow the terminologyof Upperparts:The "V" marksare whitish Humphrey and Parkes (1959), further stripeson the backof somepeeps that are SIZE discussedas it appliesto shorebirdsby derivedfrom white fringesto the mantle Palmer (1967). feathers,scapulars, or both. Depending LVatOUGhXnErange in size between In discussionsof peepidentification, it on how thesefeathers are lying, the "V" the largestspecies (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 whichfeathers are otherspecies are small and usually diffi- referred to under a collective term. For involved. cult to judge. The sandpipersin this example,of the five rowsof scapularson Underparts:The "breast sides" include groupare sexuallydimorphic in size(fe- peeps,the upperthree rows are often col- the featberingabove the flanks, or just malesslightly larger), and the apparent ored differently from the lower two. aheadof andabove the bendof the wing. sizeof 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. !). Someother secondarycoverts are frequentlyvisible to otherspecies with which it is associat- instancesof terminologypeculiar to this on a standingbird, andtheir colorationis 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, lineswhich paral- to theseas simply "greatercoverts" or resultin a significantdistortion in the ap- lel the superciliumabout one-third of the "middlecoverts." The "primary projec- parentrelative size of birds that seemto supercilium lateralcrown stripe cro•n J auriculars • •._/ / hindneck _ •,.•/// "V"mark lorecrown • tg'. % • "• • • • •ntte lo•s•-• ' ••• • upperscapulars culmen• . •.•• • lowerscapulars. •rima chin • • • ' n• • -• •• ' ' thro•'t•• • , • • --• •- • • projectto• • • • • • .•ertail cover. lessercoverts • • • •• •vent fia•ks• •-• • •greatercovertx middle toe outerinner toetoe be!•••. tar•••e•••ncoverts Figure 1. Topographyof a Calidris. 214 American Birds, Summer 1987 be standingnext to one another.There- Westernsandpipers. One shouldbeware Little stints,by comparison.have finely forethe proportions,rather than the size of birdsthai lack webbingbut acquirea tipped bills. perse,are more useful in determiningthe "club-footed" look as a result of mud The extentof the foldedprimary tips species. caked to their toes. beyondthe tip of the I,ongest 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, idcntificauon ofpeeps presenceof a rare species.Critical as- havevery little, if any, primaryprojec- dependsupon structuralcharacters 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 American species,pusilia and rnauri, pointednessas observedboth from above greaterprimary projection than Semipal- have partial webbingbetween the toes, and from the side. Lateralexpansion of mated and Western sandpipers.This whichthe similarPalearctic species. rnin- the bill tip. resultingin a slightlyspatu- charactershould probably be usedonly uta and ruficollis, lack. This feature is late condition,is typicalof the Semipal- for juvenilesin fall. asone cannotassume surprisinglyeasy to see, onceone is fa- matedSandpiper but •sonly visiblewhen thatthe primariesare completelygrown miliar with the differencein appearance the bird is viewed head-on. A blunt- in birdsof otherages. between

Load more