First Atlantic Ocean and Gulf of Mexicospeci en of Short-tailed Shearwater

AndrewW. Kratter and Florida. The onlyprevious report of was broughtto a wildlife clinic (Care & this speciesin the AtlanticOcean is a sight Rehabilitationof Wildlife, or "CROW") on DavidW. Steadman recordoff Virginiain 1998. Comparingthe SanibelIsland, Lee County, Florida. It had specimen(skin, spread wing, and skeleton) been found in weakened condition about 40 FloridaMuseum ofNatural History with a seriesof specimensof thesimilar and km west of the island in the Gulf of Mexico regularly-occurringSooty Shearwater (Puffi- by a fishingboat caprained by JoeDonker- RO. Box 117800 nusgriseus), the identification as Short-tailed sloot. Because the shearwater's condition Shearwateris basedon eightskeletal meas- never improved,it was euthanizedon 7 UniversityofFlorida urements,one qualitative skeletal character, August2000. The staffat CROWlogically three skin measurements,and the color of identifiedit asa SootyShearwater (Puffinus Gainesville,Florida 32611 the medianand lesserunderwing coverts. griseus),the only all-darkspecies of shear- Giventhe timingand typicalpath of Short- water known from Florida (Stevensonand tailedShearwater migration in the Pacific,it Anderson1994). ABSTRACT seemslikely that the Florida bird was Upon receiptof the frozenspecimen at An individual of an all-dark, medium-sized attemptinga "normal"northbound migra- the Florida Museumof Natural History shearwater,recovered alive from the Gulf of tion but was in the Atlantic rather than the (UF), Kratter noticed that it had duskier Mexicooff southwesternFlorida on 7 July Pacific Ocean. underwingcoverts than is typicalin Sooty 2000, is the first specimenof Short-tailed Shearwater.He suspectedthat it couldbe a Shearwater(Puffinus tenuirostris) in the INTRODUCTION Short-tailed Shearwater (P. tenuirostris), Atlantic Ocean basin, the Gulf of Mexico, On 7 July2000, a darkmid-sized shearwater althoughaway from the Pacificand Indian

Figure1. Underwingsofdark Puffinus shearwaters. Top,Short-tailed Shearwater (UF41873; off southwestern Florida, 7July 2000); bottom,Sooty Shearwater (UF 39963; Florida, Brevard County, 9 June 1997).

VOLUME57 (2003) NUMBER2 277 Oceans,this species was known only from a and mantle very dark brown (10YR 2/2). replaced.A numberof NorthPacific spec- singlesight report from Virginia (Marchant The ventralplumage is lighter,mostly dark imens of Short-tailed Shearwater with andHiggins 1990; A.O.U. 1998;Iliff 1998; gray (10YR 4/1) to dark grayishbrown activewing molt and no bursa (like UF Brinkley et al. 2001). Differentiating (10YR 4/2), with the throat paler (light 41873) may representthird-year (TY) betweenSooty Shearwater and Short-tailed brownishgray 10YR6/2 to grayishbrown birds. We have found no North Atlantic or Shearwateris a substantialproblem in the 10YR 5/2) and the undertailcoverts very Pacificspecimens of SootyShearwater with field, whereas the smaller size of Short- dark brown (10YR 2/2). The freshrectrices activewing molt and no bursa. Most of the tailedShearwater (e.g., seeMarchant and are very dark brown (10YR 2/2). The specimenswithout a bursahave all fresh Higgins 1990) should make specimen remigesof UF 41873 arein activesymmet- remigesand rectrices;these are probably identificationstraightforward. Kratter pre- rical molt with ppl-5 new, p6 sheathed, breeding-agebirds. Age of firstbreeding is pareda roundskin, spread wing, and par- andpp7-10 veryworn; the secondariesare 5-7 yearsin Short-tailedShearwater and tial skeleton from the specimen (UF all very worn (Figure 1). New and Sooty Shearwater(Schreiber and Burger 41873; Figure 1) in late January 2001. sheathedremiges are black (10YR 2/1) to 2001). Heart, liver, and muscletissues were saved very dark brown (10YR 2/2) aboveand Most skins of Short-tailed Shearwater and frozen. In this paperwe presentevi- dark gray (10YR 4/1) to very dark gray andSooty Shearwater at UF andUWBM do dence for the first confirmed occurrence of (10YR3/1) below.Worn remigesare dark not include data on the bursa; therefore, Short-tailed Shearwater outside of the grayishbrown (10YR 4/2) to very dark we did not attemptto put theseinto age Pacific and Indian Oceans. This record grayishbrown (10YR 3/2) aboveand gray classesas we have for the spread-wing wasaccepted by theFlorida Ornithological (10YR 5/1) to dark grayishbrown (10YR specimensbelow. The very dark brown Society'sRecords Committee (R. Bowman, 4/2) below. New and sheathedgreater crown and face of UF 41873 is similar to in litt. 2002). upperwingcoverts (ppl-5 and a few sec- that in two (of 23) specimensof Short- We comparedthe study skin, spread ondaries) are black (10YR 2/1); worn tailedShearwater and eight (of 28) of Sooty wing, andpartial skdeton of UF 41873 to covertsare very dark grayish brown (10YR Shearwater.Ihe grayish-brownthroat of similarpreparations of Short-tailedShear- 3/2). The greaterunderwing coverts are UF 41873 resembles that in one other waterand SootyShearwater specimens at gray(10YR 5/1), whereasthe medianand Short-tailed Shearwaterand 10 Sooty UF and the University of Washington lesserunderwing coverts are grayish brown Shearwaters. The throats of most Short- Burke Museum of Natural History (10YR 5/2) to brown (10YR 5/2). There tailed Shearwaterare grayerthan in UF (UWBM). Osteologicalterminology fol- wasno bodymolt. 41873. lows Baumd et al. (1993). We pooled The bill in Short-tailed Shearwater is sexes in our statistical comparisons Confirmingthe identification smaller than in Sooty Shearwater,with becausethe sexesdiffer very little in size; The speciesmost similar to UF 41873 are exposedculmen, width at distalnares, and for each of seven mensural characters in SootyShearwater and Short-tailedShear- lengthof the nail all significantlydifferent Short-tailed Shearwater, the means of water. Both are mid-sized shearwaters with (p<0.001 in t-Tests);exposed culmen and malesand females differed by nomore than all-darkplumage (dark brown to black), nail length show no overlap. UF 41873 1.5%(Marchant and Higgins1990). althoughthe throatscan be lighter. Typi- fallswithin therange of Short-tailedShear- cally,Sooty Shearwater is largerand has water for all three bill measurements and is IDENTIFICATION whitish lesser and median underwing outside the 95% confidenceinterval (mean coverts,whereas Short-tailed Shearwater is _+1.96 standarddeviations units) of Sooty Descriptionofthe bird smallerand hasdarker underwing coverts Shearwaterfor exposedculmen and nail (Figure 1), although variants can have length. Althoughthe boneyrostrum and ter in the genusPuffinus, with a relatively white coverts (Harrison 1983). Both mandible of UF 41873 were left within the long and narrowbill with a dorsalnasal speciesbreed on islandsin the temperate skin and thus not available for measure- tube (shorter,deeper, and broaderbill in southernhemisphere, with SootyShearwa- ment,their lengths in skeletalspecimens of Procellariaand Pterodroma),long, narrow ter in both the Atlantic and Pacific Oceans, SootyShearwater and Short-tailedShear- wings(Figure 1), and a shortsquared tail and Short-tailed Shearwater restricted to waterdo not overlap,reinforcing the diag- (longerand wedge-shaped in Bulweria).A islands off eastern Australia in the south- nostic value of bill measurements. malewith graytestes not enlarged(3 x 2 western Pacific (Marchant and Higgins To comparewing lengths, we limitedthe mm), theemaciated specimen weighed 363 1990, A.O.U. 1998). Followingbreeding, samplesto birdsthat, like UF 41873,had g, althoughit still had light subcutaneous bothspecies migrate into temperatenorth- worn outerprimaries. The distancefrom fat. The bird lacked a bursa of Fabricus. em hemispherewaters during the boreal the longestgreater primary covert on the Other all dark Puffinus shearwaters• summer,generally following the clockwise underwingto the tip ofpl0 is 118 mm in Wedge-tailed(P pacificus),Flesh-looted (P currentsin theNorth Pacific (both species) UF 41873, compared to 112-127 mm carneipes),Christmas (P nativitatis),Hein- or NorthAtlantic (Sooty Shearwater). (N=23) in Short-tailed Shearwater and roth's (P heinrothi),and Mediterranean (P The moltpattern of UF 41873is proba- 126-131(N=12) in SootyShearwater. yelkouanmauretanicus) shearwaters--dif- bly typicalfor a SootyShearwater or Short- We scoredthe color of the greaterand fer substantiallyfrom UF 41873 in size, tailed Shearwaterin its third (austral) win- median secondaryunderwmg coverts on proportions,plumage, soft part coloration, ter. Duringthis season, when both species 31 specimensof SootyShearwater and 70 and/or skeletal characters (Kuroda 1954, are in the North Pacific (seebelow), hatch- of Short-tailedShearwater. In general, Crampand Simmons1977, Hadden1981, year(HY, assuming that birds are born after Short-tailed Shearwater has darker median Harrison 1983, Marchant and Higgins 1 January)specimens have large bursae, covertsthan Sooty Shearwater, though pale 1990, Seto 2001). and all remigesand rectricesare fresh. A variants in Short-tailed Shearwater(9 of 70 The dorsalplumage of UF 41873 is numberof specimensof bothspecies with scoredas grayish white and two aswhite) mostly very dark brown (Munsell Soil smallerbursae and active primary molt overlap with darker variants of Sooty Color Charts 10YR 2/1 black to 10YR 2/2 probablyrepresent second-year (SY) birds, Shearwater(14 of 31 scoredas grayish very dark brown),with the crown,nape, with very worn juvenileprimaries being white,the othersbeing white). The gray-

278 N0 'R' T H:•::•' A•'I• RI CA N BIRDS ish-brown median coverts of UF 41873 are (Marchantand Higgins1990). At these ine Smith, and Sievert Rohwer, for access darkerthan in all 31 specimensof Sooty high latitudes,where there are no conti- to their collection.Conversations with Jon Shearwaterand matchedmost closely by nental barriers to east-west movement Dunnclarified the identification of Puffinus five specimensof Short-tailedShearwater and the oceanbasins merge, the strong shearwaters.Ferry Taylorprepared the that have brownish-graymedian coverts. and constant westerly winds provide skeletalspecimen. In contrast,the gray greaterunderwing ample power to displace individual coverts of UF 41873 are similar to those in seabirds.Northbound migrations into the Literaturedted manyspecimens of both species(14 of 31 "wrong"ocean basin already are known AmericanOrnithologists' Union [A.O.U. ]. SootyShearwater and 23 of 70 Short-tailed for Short-tailed Shearwater in the form of 1998.Check-list of North American birds. Shearwater). rare but regularrecords in the northern Seventh edition. American Ornitholo- Lookingat the skeleton,the margocau- Indian Ocean (Marchant and Higgins gists'Union, Washington, D.C. dalis of the humerus is rounded in Short- 1990) and one well-documentedsight Baumel,J. J., A. S. King,J. E. Breazile,H. E. tailed Shearwaterand UF 41873, whereas report off Virginiain 18 January1998 Evans,and J. C. VandenBerge. 1993. it is sharperin SootyShearwater. All other (Brinkleyet al. 2001). One otherprocel- Handbookof aviananatomy: nomina osteologicaldifferences that we couldfind lariid that breedsonly in the temperate anatomica avium. Second edition. Publi- betweenSooty Shearwater and Short-tailed southwest Pacific has been recorded in the cationsof theNuttall Ornzthological Club Shearwaterare quantitative;this similarity North Atlantic: a Buller's Shearwater No. 23. hadbeen noted by Kuroda(1954). Short- (Puffinusbulleri) was photographedoff Brinkley,E. S.,J. B. Patteson,and C. Turner. tailedShearwater (N=5-9) is significantly NewJersey in October1984 (Paxtonet al. 2001. Short-tailedShearwater (PuJfinus smallerthan SootyShearwater (N=12-19) 1985). An occasionalnorthbound migra- tenuirostris)at Norfolk Canyon. Raven in all 10 elements that we measured (ros- tionin thewrong ocean basin is alsolikely 71: 84-89. trum, mandible, humerus, coracold, ulna, for two otherspecies that breedonly in Cramp,S., and K. E. L. Simmons(eds). radius,carpometacarpus, femur, tibiotar- the South Atlantic: Wilson's Storm-Petrel 1977. Handbookof thebirds of Europe, the sus,tarsometatarsus). Eight of theseele- (Oceaniresoceanicus) rarely but regularly MiddleEast, and North Africa: the birds of mentshad no overlapin thesamples meas- occurs off the Pacific coast of North Amer- thewestern Palearctic. Vol. 1, Ostrichto ured. UF 41873 is outsidethe rangeof ica in the boreal summer (A.O.U. 1998), Ducks.Oxford University Press, Oxford, SootyShearwater for all eight measured and the Greater Shearwater(Puffinus UnitedKingdom. charactersand within the rangeof Short- gravis) has been recordedfour times off Hadden,D. 1981. Birdsof the North tailed Shearwater for seven of these (the the West Coast (A.O.U. 1998, K. L. Gar- Solomons.Wau Ecology Institute, Hand- rostrum and mandible could not be meas- rett, pets. comm.). book No. 8. ured in UF 41873 because the bill The occurrence of a Short-tailed Shear- Harrison,P. 1983. Seabirds.Houghton remained with the skin). The tibiotarsusof water on the Gulf Coast of Florida, Mifflin Co.,Boston, MaSsachusetts. UF 41873 is 0.6 mm longer than the althoughunique and surprising,under- Iliff, M.J. 1998. Winter season: longestof sevenShort-tailed Shearwaters scoresthe exceptionalability of procellari- MiddleAtlantic Coast Region. Field measured,but still outsidethe rangeof the iformsfor long-distancevagrancy. Birders Notes 52: 178-184. SootyShearwaters measured. and researchers in Atlantic waters should Kratter,A. W., T. Webber,T. Taylor,and D. now be on the lookoutfor thisspecies but W. Steadman.2002. Newspecimen- EVIDENCEON ORIGIN shoulddo soonly with a greatdeal of cau- based records of Florida birds. Bulletin Pelagicbirds have been known to hitch tion: separatingShort-tailed and Sooty ofthe Florida Museum of Natural History rideson ocean-goingvessels and end up at Shearwatersposes one of North America's 43: 111-161. far ports,but thisis probablynot how UF mostdifficult problems in field identifica- Kuroda,N. 1954. Onthe classification and 41873 arrived in the Gulf of Mexico. tion. This record also underscores the phylogenyofthe order Tubinures, particu- Given the migrationroutes of Short-tailed tremendous,largely untapped resource for larlythe shearwaters (Puffinus), with spe- Shearwaterand the season of captureof the documentingavian distributional records cialconsiderations ontheir osteology and specimen,the bird wouldhave had to stow via wildlife rehabilitation clinics across the habitdifferentiation (Aves). Tokyo, Japan. awaysomewhere on its northboundflight continent. In Florida alone, more than 120 Marchant,S., and P J. Higgins.1990. in the western Pacific, then cross the clinics are licensed to handle birds; the Handbookof Australian,New Zealand & immense Pacific and go through the staffat the FLMNH hasresources to regu- Antarcticbirds. Vol. 1, Ratiresto Ducks, PanamaCanal to the Ariantic,staying on larly visit only six or so of theseclinics PartA, Ratiresto Petrels. Oxford Univer- board until off Florida in the Gulf of Mex- annually,retrieving hundredsof frozen sityPress, Oxford, United Kingdom. ico. It is unlikelythat a bird couldsurvive specimens.Fortunately, many of thestates Paxton,R. O., W.J. Boyle,Jr., and D. A. such a lengthyjourney and then muster birderspass the wordwhen a rarity shows Cutler. 1985.The Fall Migration: the powerto fly away. up at other clinics,and we havebeen able Hudson-DelawareRegion. American We believeit morelikely that UF 41873 to documentmany important records from Birds 39: 31-36. was blown eastward across the southern specimenssalvaged at wildlife clinics Schreiber,E. A., andJ.Burger (eds.). 2001. oceans from southern Australia (or even (Kratter et al. 2002). Biologyof MarineBirds. CRC Press, Boca farther south, see below) to the southern Raton, Florida. Atlantic during the austral summer or Acknowledgments Seto, N. W. H. 2001. ChristmasShearwater autumn, where it could have joined We thankJoe Donkersloot for recovering (Puffinusnativitatis). In TheBirds of North northboundSooty Shearwaters migrating the specimenand bringing it to CROW.EJ. America,No. 561 (A. Pooleand E Gill, into the western North Ariantic. Non- Deitschel and Anita Pindar at CROW eds.).The Birdsof North America,Inc., breedingShort-tailed Shearwaters, such as kindly donatedthe specimento UE We Philadelphia,Pennsylvania. UF 41873, would be especiallylikely to thankthe staffof the Universityof Wash- Stevenson,H. M., and B. H. Anderson. follow this path, as they occurregularly ingtonBurke Museum, particularly Chris 1994.The Birdlife of Florida University off Antarctica in the austral summer Wood, Rob Faucett, Chris Filardi, Cather- Pressof Florida,Gainesville, Florida. •

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