Occurrence and abundance of tubenoses (Procellariiformes)at Guadeloupe, Lesser Antilles, 2001-2004 the Guadeloupearchipelago, French West ATS65HD spottingscope with a 20-60x AnthonyLevesque Indies. Preliminary experience in mainland zoomlens used at 30x duringsearch, occa- R•serveNaturelie des ilets de la Petite-Terre Francehad taughthim that seawatching sionallyswitched to highermagnification for froma coastalvantage point might be pro- identification of distant birds. Within each andAssociation AMAZONA ductive--providedone is armedwith pa- dockhour from 0600 to 1800(plus a minor- tience,good optical equipment, and some ity of earlyand late sessions from 0530 and Labrousse luck. Not longafter beginning m February up to 1830in latespring and summer), two 97190Le Gosier 2001, his effort was rewarded,and within consecutive15-minute survey periods were three months' time, the numbers of separatedby a breakof up to threeminutes. Guadeloupe,French West Indies tubenoses he recorded had redefined the re- The originalprotocol called for evendistri- gionalstatus of several species. A year-round bution of 15-minuteperiods across days, ([email protected]) survey was thusset up, then repeatedin months,and yearsfor consistentcoverage. 2002, 2003, and 2004 in order to determine Actual observation effort deviated from this bothconstancy and interannual variation in modelbecause main passageperiods were Pierre Ysou the occurrenceof the area'sseabirds. In all, givenextra coverage for better quantification OfficeNational de la Chasse ninespecies of tubenose(Procellariiformes) and because wardening responsibilities fortu- wereobserved during this survey. itouslyleft morefree time early and late in etde la Faune Sauvage theday, when movements were heaviest (Fig- Uethods ures1, 2). Samplingwas done with the tele- 53,rue Russell Observations were carried out from the islet scopepointed to the south(_+20 ø according 44000Nantes of Terre-de-Bas,part of Petite-TerreNature to sunglare), but it wasbriefly shifted to fol- Reserve,which lies betweenthe islandsof low birdsfor identificationor [or counting France Desira& and Mane-Galante at the southeast- and then restored. Simultaneous observa- erncorner of theGuadeloupe archipelago; at tionsfrom the studysite and from a boatat 16ø 15' N 61ø 7' W, thisis alsoone of the east- seausing GPS indicated that the relative sizes Abstract ernmostpoints on Guadeloupe (Map 1). ]'he of shearwaterswere identifiable by telescope This paper presents observationsof Continental Shelf is rather narrow east of up to4 nmi(7.4 km) offshore and that much tubenoses(Procellariiformes) of nine species Perre-de-Bas,with oceansea-floor depths of of the visiblepassage occurred within 1-3 recorded2001-2004 in year-roundseawatch- 20 m, 88 m, 376 m, and 456 m at distances nmi (1.8-5.5km) fromshore. Specific identi- esfrom Terre-de-Bas, part of Petite-TerreNa- one,2, 3, and 4 nauticalmiles (nmi) offshore ficationwas based on plumageand structur- ture Reserve,located between the islandsof (1.8, 3.7, 5.5, and 7.4 km), respectively(M. al characters(Harrison 1985, 1987; Raffaele D•sirade and Marie-Galante in the Guade- D•varieux. pets. loupearchipelago. The contextof theseob- comm.).Prevailing lo- __ servations,both historically(for Guade- cal winds are trades loupe)and regionally in theLesser Antilles, is also considered herein. andeasterlythus havecomponenta strong • ' that variesfrom north- Introduction Althoughpelagic seabird enthusiasts tend to erly,easterlybut towindssoutheast- have a i- considerthe CaribbeanSea an avifaunally true easterlydirection poorenvironment (e.g., Ballance 2004), the about 30% of the time. eastern,Atlantic-facing coasts of the Lesser Wind speed ranged Antillesin facthost a varietyof shearwaters from 18-30 km/hr and petrels,many of thesebeing migratory 60% of the time, speciesthat nestin the North Atlanticor reaching30-qO km/hr SouthAtlantic Ocean. Summarizing these about 2% of the time; species'status, Raffaele et al. (1998) noted Juneand July are the that manywere under-represented in the lit- windtest months. erature,owing to their occurrencefar off- The samplingpro- shore.For example, they regarded Audubon's tocol required 15- Shearwater(Puffinus lherminieri) as "not minute nonstopob- likelyto be seenexcept from a boatfar off- servationfrom the top shore" (Raffaele et al. 1998). of thehighest cliff (ca. kevesquebegan to lookfor seabirdsfrom 7 m above sea level) shorein 2001,when he assumed his position with a tripod-mount- Map1. All observations treated inthis paper were made on the small island of Terre-de-Bas as a warden at Petite-Terre Nature Reserve in ed Swarovski AI80 or betweenthe islands of D•siradeand gafie-Galante inthe Guadeloupe archipelago. 674 NORTH AMERICAN BIRD 7O beatsthan Manx--and these bursts of flap- ping were also of greaterduration than Manx's.This flight behavior is typicalof the speciesin both low windsand a! higher wind speeds.While the firstauthor was re- sponsiblefor mostof the fieldobservations, thesecond author, who has extensive expe- riencewith Atlanticshearwaters, joined for thesurvey for 10days m April2004 to veri- fy identificationcharacters. Withoutexception, when birds occurred closeenough to shoreto allow plumage charactersto be studied,we found that the identificationbased on plumagecharacters correspondedto the identificationbased on Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec flightaction and structure. Pelagic trips in spring2004 (up to 33 nmi [60 km] offshore) Figure1. Distributionofthe observation effort per month. The effort was kept low in autumn (down to 11 hours inOctober, i.e. were also conducted in order to check the onaverage one 1S-minute observation period every three days) due to the very low frequency ofbirds detected atthat time of the year;the effort was intensified during periods that proved tobe most productive. identification characters used in shearwater and storm-petrelidentification; seabirds 80 were attracted close to the vessel with fish 70 oil andsmall pieces of fish. 60 eumberofhours withobservaaon Dataobtained during each 15-minute pe- 50 riod, includingall samplingzeros, were 40 pooledper hour and per month,leading to the calculation of the mean number of indi- 30 meannumberofbirdsperhour vidualsof a givenspecies observed per hour 20 duringa givenmonth. Multiplied by the 10 numberof hourswith daylight and the num- 0 ber of daysper month.this databasealso one-hour period permitsa roughestimate of the numberof birdsthat passed through the study area over Figure2. Distributionofobservation effort and average bird frequency through the day. The observation effort peaks in a givenperiod. thefirst and last part of the day due to work schedule onthe Nature I•eserve, leaving more free time before 8 a.m. and afier S p.m.Low observation effort in the very first and last hours ofthe day is linked to seasonal variations indawn and sunset time. Resultsin Context Themean number ofbirds per hour tends to decrease throughout theday (r = -0.71). Shearwalersand petrels From April 2001 to December2004, 7513 etal. 1998;Sibley 2000), but flight behaviors straightwings and longglides on slightly shearwatersand petrels (Procellariidae) were werealso carefully scrutinized and eventual- archedwings; its trajectoryarcs above sea sampledduring 380 hoursof seawatching; ly alsoused for identification.At suchdis- levelduring the glideas wind strengthens, 88 percent of these(6611) were identified to tances,for instance,distinguishing Manx andunder strong winds it mostlyglides, arc- species.Unidentified birds were scoredas (Puffinuspuffinus) from Audubon's Shearwa- ingsharply upward from the sea surface up "largeshearwaters" (Cory's/Greater) or tersbased on plumagecharacters was often to manymeters high, then veering sharply "small black-and-white shearwaters" challenging;structure and flight patterns downwardagain. Conversely,Audubon's (Manx/Audubon's)(Table 1). were thus the main features used to tell these Shearwater undertakes much shorter. shal- Black-cappedPetrel (Pterodromahasita- speciesapart. Manx Shearwater alternates a lowerglides on morearched wings, inter- ta)--Three individualswere seenin early brief seriesof strong,shallow beats of spersedwith frequentseries of fasterwing- 2004 (7 and 14 January,4 February);four Table1. Monthly distribution ofshearwaters, petrels, and storm-petrels offPetite-Terre, Guadeloupe, 2001-2004, withlevel of sea-watching effort (hours per month). Numbers insquare brackets indicate unconfirmed identifications. Jan Feb Mar Apr May Jun Jul Aug 5ep Oct Nov Dec TOTAL ManxShearwater 5 85 2245 139 56 4 3 6 2543 Audubon'sShearwater 3 3 2 98 339 125 3 1 2 2 3 581 Manx/Audubon'sShearwater g 20 30 49 49 30 3 I 5 5 5 206 Greater5hearwater 3 1547 501 2051 Cory'sShearwater 1 2 18 463 91 5 42 5 627 Sooty5boarwater 1 5 3 I 10 Greater/Cory'sShearwater g 268 88 2 7 3 377 Black-cappedPetrel 2 1 3 gadflypetrel (œterodroma sp.) 2 1 1 4 Bulwer'sPetrel 1 [+1] [1] 1 [+2] Wilson'sStorm-Petrel 3 63 359 282 51 4 1 2 765 Leach'sStorm-Petrel 5 26 14 1 46 unidentifiedstorm-petrel 7 33 97 138 1g 1 I I 297 Totalnumber of birds 22 121 2379 770 913 2513 692 8 1 11 60 23 7513 Totalnumber of hours 25.5 31.25 37 30.25 50.25 60 45.5 32.5 13.25 11 18.75 24.75 380 VOLUME 59 (2005) NUMBER 4 675 moregadfly petrels (Pterodroma sp.) seen in list of speciesrecorded in Guadeloupeyet: passeast of Guaddoupeeach year. Until the the sameperiod were also most likely this accordingto the criteriain placefor the presentstudy, this specieswas considered species.Black-capped