THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC. VOL. 31 DECEMBER 1997 NO. 4 j RaptorRes. 31 (4):303-307 ¸ 1997 The Raptor ResearchFoundation, Inc. OBSERVATIONS OF RAPTORS IN THE REPUBLIC OF VANUATU WADE L. EAKLE 1 WorldWorking Group on Birdsof Preyand Owls,Wangenheimstr. 32 D-14193 Berlin,Germany ABSTRACT.•Roadand trailsidesurveys were conductedin the Republicof Vanuatu,formerly known as the New Hebrides in the SouthwestPacific, to determine relative abundanceof raptors.Three diurnal and one nocturnalspecies were observedduring 74 hr of observationover 594 km surveyed.Swamp Harriers ( Circusapproximans approximans) were mostfrequent and found on all islandssurveyed includ- ing Efate (N = 6), EspirituSanto (N-- 31), Gaua (N = 11) and Tanna (N = 19). PeregrineFalcons (Falcoperegrinus nesiotes) were observedon Gaua (N = 2) and Tanna (N-- 1), while Brown Goshawks (Acdpiterfasdatusviligax, N = 2) and Barn Owls (Tyto alba interposita,N = 2) were observedon Tanna and Espiritu Santo, respectively.Observations of SwampHarriers on Gaua and Brown Goshawkson Tanna are the first reported for these specieson these islands. Indices of relative abundance were calculatedfor each speciesbased on the number of individualsobserved per km traveled. K•Y Worn)s: BrownGoshawk; Accipiter fasciatus viligax; raptor roadside survey; relative abundance;, Swamp Harri• Circus approximans approximans; Vanuatu. Observacitnesde rapace en la Republica de Vanuatu R•suM}•N.--Estudiosde caminosy callesfueron conducidaden la Republicade Vanuatu antesconocido como Nuevo Hebrides en el Pacifico del Sud-oeste,para determinar la abundancia relativamentede rapace.Tres especiedel dia y uno de la nochefueron observadosdurante 74 hr en una region de 594 km. Circusapproximans approximans fueron masfrecuente, y locolizadosen todaslas islas inspeccionadas incluyendoEfate (N = 6), EspirituSanto (N = 31), Gaua (N = 11), y Tanna (N = 19). Falcopereginus nesiotesfueron observadosen Gaua (N = 2) y Tanna (N = 1), fueron observadosen Tanna y Espiritu Santo, respectivamente.Observacitnes de aguiluchosen Gaua y Accipiterfasdatusviligax en Tanna son las primerasespecie reportadas en estasislas. Indice de abundanciarelativa fueron calculadaspara cada especiebasado en numero de individualesobservados por km caminados. [Traduccitn de Rafil De La Garza,Jr.] Tropical rainforestsare perhapsthe mostbiolog- habitats, population numbers and trends, and en- icallyrich terrestrialhabitats in the world.Thiollay vironmental factors limiting their numbers. Burn- (1994)estimated that over 46% 'of the world's pres- ham and Cade (1995) recently suggestedthat ently recognized falconiforms are tropical forest more attention should be focusedon speciesthat species.Tropical forest raptors, including strigi- are little known and needing study and in geo- forms, are also much less known than Nearctic and graphical"hotspots," because those species and lo- Palearcticspecies, and in need of further studyto cations are most likely to be, or are soon to be- better understand their basic biological and eco- come, jeopardized through continued human en- logical requirements,including densityin certain croachment and development. Though not recognizedas a geographical"hot- 1Present address:U.S. Army Corps of Engineers, spot" for its high biodiversitylike the nearby is- South Pacific Division, Regulatory Program Office, 333 lands of New Guinea and New Caledonia, the Re- Market Street, San Francisco, CA 94105-2197 U.S.A. public of Vanuatu is an important faunal cross- 303 304 E•CLE VoI•. 31, No. 4 roads where the main streams of colonization of Standardized road and trailside counts were conducted SouthwestPacific birds meet (Bregulla 1992). This on the islandsof Efate, Espiritu Santo, Gaua and Tanna using a car and on foot from 19 October-7 November nation of large and small islandshas received little 1996 (Fig. 1). Three to four observerswalking and trav- attention from biologistsdue in part to its remote eling together located and identified raptors on both location. Most of the residentbirds are thought to sidesof roads or trails during thesecounts, and recorded have been derived from Australia, New Guinea or data on speciesand number observed,habitat type and Fiji. Residentraptors include the Brown or Austra- activity(Thiollay 1989). Driving speedswere variable, but roadwayconditions always limited speedsto •40 km/hr. lian Goshawk (Accipiterfasdatus vigilax), Swamp When raptors were observed,the vehicle was stopped Harrier (Circus approximansapproximans), Pere- momentarilyto identify the birds. Periodicstops were grine Falcon (Falcoperegrinus nesiotes) and Barn alsomade to scanfor distantraptors in open habitatsor Owl (Tytoalba interposita and T. a. lulu). The Brah- over the forest canopywhenever conditions allowed. The location of each observationwas plotted on 1:50 000 or miny Kite (Haliastur indusflavirostris) occurs as an 1:100000 scale maps of the islands,and the d•te•'•hd occasionalvagrant from the neighboring Solomon time of each sightingnoted. Surveytimes ranged from Islands(Wattel 1973,Weick 1980, Bregulla1992). 0500-1900 H. Weatherconditions were variableduring During a related studyof Vanuatu'slargest and the surveyperiod, but mostlywithout any precipitation. Some studies have indicated that roadside and trailside most accessible islands to determine if Sanford's counts can give biased estimatesof raptor densitiesand Sea Eagle (Haliaeetussanfordi), thought to be en- habitat associations. However, road counts can be useful demic in the Solomon Islands, occurs in the ar- and appropriate when large areasneed to be sampled chipelago as a resident or vagrant species,I also and monitored (Fuller and Mosher 1987). Use of road- soughtto determine the distribution of the islands' waysand trails on Vanuatuwas the only feasiblemeans of satisfyingthe studyobjectives. birds of prey, and estimatetheir observedrelative I used the method developedby Woffinden and Mur- abundance. Here, I used numbers of individuals phy (1977) to calculatean index of observedrelative observedper km traveled,and numbersseen per abundancefor each raptor speciessighted: hr of observation, to estimate relative abundance Index = [ (Total number of a speciesobsepeed) during a roadside and trailside survey.This may -' (Total km traveled)] X 1000 not have been done previouslyfor the islands. STUDY AREA AND METHODS RESULTS AND DISCUSSION Located between the equator and the Tropic of Cap- Nearly 600 km were traveledand 74 hr of obser- ricorn (13-23øS,166-173øE), the Republicof Vanuatuis vation time logged (Table 1), givingan averageof a chain of about 100 ash and coral uplifted islandsand islets. They were formerly known as the New Hebrides 1.0 raptors sighted per hr of observationtime, or until 1980 when independencewas gained from the con- 0.12 individualssighted per km (8.0 km traveled dominium governmentsof France and the United King- per bird sighted). dom. The Y-shapedarchipelago of mainly smallvolcanic Swamp Harriers were most common and ac- islandsoccurs in one of the mostgeologically active areas in the world,and ispart of a continuousisland arc system countedfor 90% of the raptorssighted (Table 2). stretching from Papua New Guinea and the Solomon Is- Bregulla (1992) suggestedthe SwampHarrier was lands to Fiji and Tonga. The largestisland is EspirituSan- the largest raptor in Vanuatu, and found on most to with a surfacearea of 3900 km2. Other major islands islands,except Gaua, Mota Lava, Mere Lava and include Efate (915 km9), Gaua or Santa Maria in the Tongariki. Also known as the Pacific Marsh Harri- Banks Islands group (310 km9) and Tanna (572 km9) er, Areadon et al. (1988), Olsen (1995) and Clarke whichare mountainousand extremelyrugged. The high- est peak in Vanuatuis Mt. Tabwemasanaon EspirituSan- (1995, 1996) suggested,and others (Grossmanand to at 1879 m (Fig. 1; Bregulla1992). Hamlet 1964, Brown and Areadon 1968, Watson Vanuatuhas a wet, tropicalclimate in the north grad- 1977,Weick 1980, Cupper and Cupper1981) ear- ually changingto subtropicalin the south,and largely lier treated, the SwampHarrier and three other exposed to prevailing southwesterlywinds. Evergreen rainforestcovers about 75% of the country.Three major Circusspecies as a complex, conspecificwith the plant communitiesare readilyrecognized on the larger widely distributed Western Marsh Harrier (C. aeru- mountainous islands,including evergreen tropical rain- ginosus)of Europe, North Africa and the Middle forest on the lowland,warm, wet, windwardslopes; semi- East.My observationsof SwampHarriers (N = 11) deciduousforest and fire-inducedsavannahs and grass- on Gaua suggestthe speciesmay be extending its lands on lowland,warm, drier, leewardslopes; and ever- green forest on upland and summit areas with cooler, range in the archipelagoto previouslyunoccupied wetter and more humid climatic conditions (Bregulla islands.Alternatively, Swamp Harriers may have 1992, Harcombe and O'Byrne 1995). been present,but simplyunobserved during pre- D]•C]•MB]•]• 1997 R•TO]•S IN V•a,•U^TU 305 REPUBLIC OF VANUATU 0 50 1 O0 [•TORRESISLANDS KILOMETERS LAKE • LET•.•/ •0 • UREPARAPARA GAUA •:• MOTALAVA 0 10 20 30 VANUALAVA•3(3 KILOMETERS BANKS ISLANDS E•A'•E EFATE KILOMETERS 0 10 20 30 KILOMETERS ERROMANO0 '• COR A L i......•I;,'• \VANUATUREPUBLIC ßOF .:. TANNA 0 10 20 50 AUSTRALIA/ PA C IF IC 0C EA N ANEITYUM• KILOMETERS • j' TASEAS M A N '•EWZEALAND Figure 1. Raptorsurvey routes in the Republicof Vanuatu,19 October-7November 1996. 306