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Field identification of Little and Saunders’s Tern Klaus Mailing Olsen and Hans Larssen Resume: La separation sur le terrain des sternes, particulierement des especes superficiellement similaires, peut s’averer ardue meme pour les observateurs les plus experimentes. Les similarietes nombreusesentre certainesespeces, combineesau defipeut-etre impossiblede separerles plumages des oiseaux n’etant pas en periode de reproduction, resultent souvent dans le fait qu’elles sont consignees dans les carnets de notes simplement sous forme d’“especes de sternes” ou purement et simplement omises. Le present article, adapte exclusivement pour ABC du nouveau guide Terns of EuropeandNorthAmerica(Helm)traitedel’undesplusgrandsproblemesquiseposeauxobservateurs enAfrique, ^identificationsurle terrain de la Sterne de Saunderset des Sternes naines. The field separation of terns, especially superfi- background, whenthetailstreamersdisappear. Dur- ciallysimilarspeciescanprovetaxingtoeventhe ing the northern summer, the tail length has been mostexperiencedbirders. The numeroussimilarities estimatedat 1.2-1.5timesthebreadthofthewingsat between certain species, compounded by the per- theirbase. haps impossible challenge of separating some Perchedbirdsareshort-leggedandcompact,with non-breeding plumages, often leads to notebook flatheaddrawndownbetweentheshouldersandthe absences orthe common entry ‘tern sp’. longbill held horizontally. The following text, adapted exclusively for ABC The Little Tern is very characteristic. Great diffi- from the award-winning new guide TernsofEurope culties arise, however, when separating the closely andNorthAmerica(Helm) deals with a most likely related species (races?), Saunders’s and Least Terns. problem facing birders in Africa: the field identifica- Identificationinwinterandimmatureplumagesisnot tionofSaunders’s SternasaundersiandLittleTern S. normallypossible even in the hand. albifrons. Adults insummerplumage have a black cap and white forehead, the latter narrowing gradually in a Little Tern Sterna albifrons triangle towards the eye. Identification in the field The loral stripe is black, broadest on males, on Little,LeastS.artillarumandSaunders’sTernsarethe whichitgraduallybecomesbroadertowardstheeye. smallest terns. The Little Tern is only the size of a Theyellowbillhasablacktipandlookslikeamatch- Ringed Plover Charadrius hiaticula and in shape stick stuck onto the head. The upperparts are pale , resembles half-sized Sandwich Tern S. sandvicensis. blue-grey with outer most 1-3 primaries forming a TheLittleTerngivestheimpressionofasmall,white, distinctblack leadingedge tothewing. The rump is over-active andalmostaggressive coastalbirdwhich palergreyandthetailpurewhite.Thelegsareyellow flies fast and purposefully. In the breeding season it toorange-yellow. FromJuly-Augustthe innerprima- alsoshows periods ofslower, elegantflight. riesaremoultedandelementsofwhiteappearinthe TheLittleTernhoversatafewmetres’heightwith crown. The bill candarken fromAugust. downward-pointing bill and plunge-dives directly Adults inwinterplumage have a dull black, grey- towards the water’s surface, rising again after a few spottedmaskwhichisdiffuselydemarcatedfromthe seconds. It usually forages over shallow water near white-flecked crown. The black spot in front ofeye theshoreline, butsometimesseveralhundredmetres standsoutagainstthewhiteloresandface.Theupper- out, where it mayhoverat heights ofupto 10m. parts are much as in summer plumage, but lesser The Little Tern is large-headed, with a long and coverts become darkerand the tail greyer. The wing narrow bill about the same length as the head. The markings depend much on the degree ofwear and pointed wings, especially seen against the light, ap- moult. Inmidwinterthebillisblack.Thelegsaregrey pear narrow with the remiges (except the dark orbrown, sometimes tingedyellow. outer-primaries) translucent. The armandhandon a Juvenilesaresmallerandmorecompactthanadults, bird in activeflight are almostuniform inwidth. The with more rounded wingtips; in the period immedi- body is streamlined and slender, with no obvious atelyafterfledgingthey recall a pale-winged Ringed centreofgravity.Thetail isshorterthanthatofother Plover, as they have a more uncertain and flapping native terns, especially when seen against a light flight than adults. In plumage they are rather like FieldID ofLittle and Saunders's Terns: Olsen &Larssen BullABCVol2No2-81 ) juvenileSandwichandRoseateTernsSternadougallii. Theupperpartsaretricoloured,withadarkerleading Little Tern Quick key to identification edgetothewing(lessercovertsandouterprimaries), pale grey or yellow-brown mantle/back and coverts 1 Only half the size of other terns. andwhitesecondariesandinnerprimaries.Theman- 2 Forehead white in all plumages, extending very narrowly to behind eye. tle/backhasblackVmarkings, whichasearlyas late 3 Bill yellow with black tip summer, are replaced by pure grey feathers. The 4 Tail and rump white, sometimes tinged grey, rump and central tail feathers are grey, with white especially on tl-3; t5-6 normally white (see outer tail feathers. Dark tips to the tail feathers can Saunders's). form a faint darkband. 5 White rump contrasts with grey back and any grey The forehead and crown initially have a yellow- tail feathers. ish-brownto cinnamon-browntinge, butsoon(from 6 In breeding season, 2-3 outer primaries are black- ish-grey contrasting with grey of rest of upperwing. July-September) become white. Looking from the 7 Juveniles and first-winters resemble half-sized central crownbackwards, grey-brown streaks merge Sandwich Terns intothedark,verynarrowfacialmask.Atcloserange bthuetabtigadeiysetaisncceletahrelyybacecceonmtueaotneedwbiytahwahbiltaeckeyter-irainnggl,e and east Asia have a white rump and tail (much as nominate albifrons). from in front of the eye. The underparts are white, sometimes with a faint brown-toned Black Tern Saunders’s Tern Sterna saundersi Chlidoniasnigerlike patch as on the breast sides. The bill is brownish-black, with a variable paler identification in the field yellowish base or edges after fledging. The legs are ThisspeciesisveryliketheLittleTern,andthereisstill greyish-yellow, sometimes orange toned. great uncertaintysurroundingitstruestatusasaspe- cies. Manyintermediatesoccurandonlythosewitha Voice combination ofall characters can be identified with Harsh; amonosyllabic ketorket-ket, orkweek, which certainty in the field - and only in adult summer isheardfrequentlyfromforagingbirds. Oftenuttered plumage. WhereSaunders’sbreedstogetherwithLit- asa double note. tle Tern, it prefers saltwater whereas Little breeds Geographical variation inland in these situations. Race guineae(WestAfrica) is generallysmaller than In adult summer plumage the most important nominate raceandthebill ismorecommonlywholly differences from LittleTern are: yellow.Rumpandtailoftengrey,t6white.Thetailcan 1 the white forehead patch extends only to the eye, be darker grey than on Saunders’s Tern. Some are whereitisroundedofforsquare-cut.Saunders’sTern inseparablefromnominate;validityoftheracepossi- lacks Little’s suggestion ofa white supercilium. The blydubious. Populationsfromthe PersianGulfoften distance from the bill base to the rear edge of the havegreyrump andtail. foreheadpatchabove theeyeis9-14mm(onLittleit Asia)Rahcaessgirneeynsrisum(ipncalnudditnlg-3p,usainldlama(Iyndsihaoawndwheiatset tishe15e-y2e0amnmd).thTehreeraeriesdugpetoof3thmemforofehbelaadckpabtecth;wetehne rump/tail(especiallyeasternpopulations);t4-5white, patch normallyreachestotheeye onLittle, oronly 1 oftenwithgreytingetoouterwebsandouterpart; t6 mmabove. The blackloralstripe is 3-6mmbroad in white(gmrmeyonfewerthan1%).Thebillisyellowwith frontoftheeye, broadestonmales(normally3-4mm upto6 ofblackattip.Unlikeotherraces,sinensis on Little). Seeillustrations. shows whitish primary shafts. The tail streamers are generallylongerthanonSaunders’sTern,beingupto 2the legsarereddish-browntomid-brownandaver- 68 mm. Many are intermediate age shorterthan on LittleTern. between Little and Saunders’s, Tailtopography 3 the upperparts are pale grey, much as on adult having LittleTern’s head mark- RoseateTern,andareconcolorouswiththerumpand ings but with a grey rump and tail. Contrast between the back and the rump/tail is tail. In structure and size, generally lacking. Little Tern has a paler rump con- sinensis seems close to Fairy trastingwithadarkerback.Thevalueofthisfeatureis Tern S. nereis of Australasia diminishedbythefactthatthoseLittleTernsbreeding and Yellow-billed Tern S. within the rangeofSaunders’soften have thecentral superciliarisofSouth America. part ofthe tail grey. However, the rump is normally t=tailrectrices The populationsfromAustralia palerandstandsoutmoreclearlyagainstLittle’sdarker 82 - BullABC Vol2 No 2 Field ID ofLittle andSaunders’s Terns: Olsen &Larssen . rump and uppertail-coverts have white edges and Saunders’s Tern Quick key to identification appear whiter. 1 Forehead patch smaller, ending in rounded or 4Thetailstreamersaregenerallyshorterandneveras square-cut rear edge in front of eye long as on long-tailedLittleTerns. 2 Upperparts paler grey than on Little Tern. No A much-debated characteris that the outerthree obvious contrast between back and rump/tail. primariesareblack(includingblackshafts)andform 3 Rump and most of the tail pale grey; only t6 is a broader, and purerblack leadingedge tothe outer predominantly white. 4 Legs darker, with brown tone. wingthanonmostLittleTerns,thisbeingaccentuated 5 Outermost 3 primaries deeper black than on Little byapalergreyupperwing.Thisfeatureshould, how- Tern, with black shafts. Contrast accenuated by ever,beusedwithcautionowingtoLittleTern’smoult paler upperparts than on Little. pattern. Birds studied in East Africa in winter did, 6 Tail streamers never as long as on long-tailed nevertheless,appeartohavemoreblackontheouter- Little Terns. most primaries (normally 3-4 outer primaries black) than Little Terns. Beware, however, moulting Little grey upperparts. Furthermore, Little Terns normally Terns with up to 6-7 inner primaries moulted and show palerbases to theirgrey rump feathers, which contrastingwith3-4outerunmoultedanddarkerones, may give a mottled appearance to the rump. On though LittleTerns normallyshow palershafts. Saunders’s, the rump is pale grey and the tail pale Adultwinterplumageis almost identical to that of grey; tl-4 pale grey, t6 white. In fresh plumage, the Little.Theupperpartsaredarkergreythaninbreeding LittleTern:adultmalesummer(topleft).Notepointed extensionsofwhiteforeheadtojustovereye,andwhiterump. Spain,June(KarelBeylevelt). Sternenaine:adultemale,ete(enhaut,agauche).Notez I'extensionpointuedufrontblancjusquejusteandessusde I’oeiletlecroupionblanc.Espagne,juin(KarelBeylevelt). LittleTern:adultsummer(bottomleft).Notetwodarkouter primariesandwhiterump.Noteoilpollution causesunusual wingmarkings.Israel,April 1994( KlausMailingOlsen). Sternenaine-.adulte,ete(enbas,agauche).Notezlesdeux remigesprimaireexterieursfoncesetlecroupionblanc.La pollutionparlepetrolecausedestachesinhabiteullessurles ailes.Israel,avril1994(KlausMailingOlsen). Saunders’sTern:adultsummer(topright).Compareshapeof Saunders’sTern:winterplumage(bottomright).Notegrey whiteforeheadwiththatofLittleandLeastTerns,notreaching centresofrumpandtailincontrasttowhitesidesofrump.In eye.Insummerplumage,upperpartspalerpearly-greythan winterplumageaveragesdarkerthanLittleTern(oppositeto onLittleTern,uniformwithrumpandcentralpairoftail summerplumage).Bahrain,autumn1990(ErikHirschfeld). feathers.Oman,May1993(HansandJensEriksen). StemedeSaunders:plumaged’hiver(enbas.adroite).Notez SternedeSaunders:adulte,ete(enhaut,adroite).Comparez lecentregrisducroupionetdelasqueueencontrasteavecles laformedufrontblancaveccelledesStemesnaineetdes cotesblancsducroupion.Dansleplumaged’hiverles PetitesStemes, n'arrivantpasaI’oeil.Dansleplumaged'ete, individussontenmoyenneplusfoncesquelaStemenaine lespartiessuperieuressontgrisperlepluspalequechezla (contrairementanplumaged’ete!).Bahrein,automne1990 Sternenaine, uniformeaveclecroupionetlapairecentralede (ErikHirschfeld) pennesrectrices.Oman,mai1993(HansetJensEricksen). FieldID ofLittle andSaunders's Terns: Olsen &Larssen BullABC Vol2No2-83 ) . season,andcanbedarkerthanonLittle(Hollometal Africa(Cramp 1985). Differences, however, aresmall 1987). The uniform grey rump andback are difficult and integrades do occur. ® featurestouseinthefield,asmanyLittleTernswithin Saunders’s range have an equallygreyrump andtail References (seeabove).Theblackmaskisgenerallybroaderthan 1. Cramp, S. (ed) 1985. Tloe Birds ofthe Western on Little (so mirrors the head pattern of summer Palearctic.Vol 5. Oxford: OxfordUniversityPress. plumage). The crown to nape is dark. 2. Hollom, P.A.D., Porter,R.F., Christensen, S. and Willis, I. 1987. Tije birds ofthe Middle East and Juvenile Probably identical with Little Tern. Some North Africa. London: T.& A.D.Poyser. (Bahrain) have, however, shown a darker bar on TernsofEuropeandNorthAmerica:Adaptedwiththe secondaries. permissionofthepublishersoftheEnglishlanguageedition, Voice ChristopherHelmLtd,asubsidiaryofA&CBlack A kit-kitor kit-ir-kit, as LittleTern’s but possiblyless ©text:KMOlsen, 1995 ©illustration:HLarsson, 1995 sharp than latter’s. Geographical variation Illustration1 (enhaut) BirdsfromthePersianGulfandArabiaareonaverage SternenaineSternaalbifrons,SternedeSaunders longer-winged than those from Pakistan and East S.(a.)saundersietPetiteSterneS.(a.)antillarum. 1 Sternenaine,jeune. 2 Sternenaine,adulte,hiver/premierete. 3 Sternenaine,adulte,ete.Tachefrontaletriangulaire Plate1(top) blanche,arrivantfrequemmentjustederrierei’oeil. LittleTernSternaalbifrons,Saunders’sTernS.(a.)saundersi 4 PetiteSterne,adulte,ete.Dessinsurlateteidentiqueacelui andLeastTernS.(a.)antillarum. delaSternenaine. 1 LittleTern,juvenile. 5 SternedeSaunders,adulte,ete.Tachefrontaleblancheplus 2 LittleTern,adultwinter/firstsummer. courteetpluscarreequechezlaSternenaine, n'arrivant 3 LittleTern,adultsummer.Whitefrontalpatchtriangular, pasderriereI’oeil. frequentlyreachingjustbehindtheeye. Illustration2(enbas 4 LeastTern,adultsummer.Headpatternidenticaltothatof 1 Sternenaine,jeune.RessemblesuperficiellementalaSterne LittleTern. caugekenminiature.Individutypiqueavecremigessecond- 5 Saunders’sTern,adultsummer.Whitefrontalpatchshorter airesblanchatresetecaillessurlespartiessuperieures. andsquarerthanonLittleTern,notreachingbehindeye. 2 Sternenaine,jeuneenmuepourpremierhirer.Apartirde Plate2(bottom) jluavfeinnildeesleetted,eplelcuomteessugrpiesrpiaeluereusntiufonrmmee.laRnegmeardqeupel:umleess 1 LittleTern,juvenile.SuperficiallylikeSandwichTernin individusavecdesremigessecondairesforcesnesontpas miniature.Typicalindividualwithwhitishsecondariesand infrequents,bienquilssoientrelativementplusfrequents scaledupperparts. parmilaSternedeSaunders.Plusderechercheestrequise. 2 LittleTern,juvenilemoultingintofirst-winter.Fromlate 3 Premierhiver/adulte,hiver.Laplupartsontinseparables summer,uppersideisamixtureofjuvenileanduniform apresdecembre-janvier.Lesoiseauxdontc'estlepremierete palegreyfeathers.Note:individualswithdarksecondaries conserventleurplumaged'hiver. afrreeqnuoetntilnyfraemquoenngt,Saalutnhdoeursg'hstTheerynm.aMyoroeccruerseraerlacthiviselymore 4 sSeterrenterencaiisnsea,ntaddeurlrtiee,reetTe.oeNiolteetzlelacrtoaucphieobnlbalnacnhce.surlefront needed. 5 Sternenaine,adulte,ete.Caracteristiqueavecunbeejaune 3 First-winter/adultwinter.Mostareinseparableafter longetminceaextremitefoncee,despartiessuperieuresgris December-January.First-summersretainwinterplumage. paleetunelignefonceeetroitesurlebordanterieurde 4 LittleTern,adultsummer.Notewhiteforeheadpatch, I'ailecreeeparl'usuredesremigesprimairesexterieures narrowingbehindeye,andwhiterump. (1)2-3-Lecroupionblancetqueueblanchepermettent 5 LittleTern,adultsummer.Characteristic,withlongand d’identifierpositivementcespecimencommeetantune slenderyellowbillwithdarktip,palegreyupperparts,and Sternenainealbifronsmaisilexistedesspecimensavecun narrowdarklineonleadingedgeofwingcreatedbyworn croupionetlespartiesmoyennesdelaqueueateinte outer(1)2-3primaries.Whiterumpandtailpositively grisatre.Cesendroitsontrarementunecouleuruniforme identifythisindividualasLittleTernalbifrons,but avecledospuisquelabasedesplumesducroupionest individualswithgreyishtingetorumpandmiddlepartsof normalementplusblanche(voirSternedeSaundersetPetite tailoccur.Theseareasarerarelyconcolorouswithback,as Sterne). basesofrumpfeathersnormallyarewhiter(seeSaunders’s 6 PetiteSterne,adulte,ete. andLeastTerns) 7 SternedeSaunders,adulte,ete Lesindividustypiques 6 LeastTern,adultsummer. peuventetreidentifiesparune.combinaisondetache 7 Saunders’sTern,adultsummer.Typicalindividualsmaybe frontaleblanchepluscourte(arrondie),n’arrivantpas identifiedbyacombinationofshorter(rounded)white derrierel'oeil,despartiessuperieuresd’ungrisuniforme frontalpatch,notreachingbehindeye,paleranduniform pluspaleetunendroitplusnoir(pluslarge)surlesremiges greyupperpartsandblacker(broader)areaonprimaries primairesquechezlaSternenaine.Beaucoupdegrada- thanonLittleTern.Manyintegradesoccurinbreedingareas tionsexistentdanslesregionsdereproductiondelaSterne ofSaunders’sTern,makingsafefieldidentificationvery deSaunders,cequirenduneidentificationprecisesurle difficult. terraintresdifficile 84 - BullABC Vol2No 2 FieldID ofLittle andSaunders’s Terns: Olsen &Larssen FieldID ofLittle andSaunders's Terns: Olsen &Larssen BullABCVol2No2-85