Extraordinary Numbers of Oriental Pratincoles in NW Australia
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Extraordinary numbers of Oriental Pratincoles in NW Australia HUMPHREY SITTERS• , CLIVE MINTON2, PETER COLLINS3, BRIAN ETHERIDGE4, CHRIS HASSELL 5 & FRANK O'CONNOR 6 •Limosa, Old Ebford Lane, Ebford, Exeter EX3 0QR, UK.hsitters@aol. com; 2165Dalgetty Road, Beaumaris, Victoria, 3193, Australia; 3RMB 4009, Cowes,Victoria, 3922, Australia; 4RoyalSociety for the Protectionof Birds,Etive House, BeechwoodPark, InvernessIV2 3BW, Scotland; 5po Box3089, Broome,WA 6725,Austrafia; 68C Hardy Road, Nedlands, WA 6009,Australia. Sitters,H., Minton, C., Collins,P., Etheridge,B., Hassell,C. & O'Connor,F. 2004. Extraordinarynumbers of OrientalPratincoles in NW Australia.Wader Study Group Bull. 103:26-31. On 7 February2004, we madean extraordinarycount of 2.88 millionOriental Pratincoles at EightyMile Beach, NW Australia.This compareswith the previousestimated population in the whole East Asian-Australasian flyway of just 75,000. We suggestthat a combinationof unusualweather and feedingconditions led to this concentrationand that the populationhas always been much more numerous than previously supposed, with mostoccurring unrecorded in the vastnessof outbackAustralia. INTRODUCTION someweeks earlier, in late December,which had produced somenew shootsof grassbut not enoughto allowit to grow The East Asian-Australasianflyway populationof the Ori- very much; i.e. most of the grasswas still quite shortand ental Pratincole Glareola maldivarum breeds in E and SE therewere somepatches that were still completelybare. Asia andmigrates mostly to Australiawhere it occursmainly We cannotbe sureas to the identity of the pratincoles' duringDecember to February.The mostrecent estimate of main prey, but they appearedto be feedingextensively on the flyway population is .75,000 (Bamford et al. 2003, Yellow-wingedLocusts Gastrimargus musicus which were WetlandsInternational 2002). abundant,though by no meansat plaguelevels (as they were The main observationsreported here were made during in late March and early April 2003 (C. Minton & D. theNW AustraliaWader and Tern Expedition2004 (organ- Hollands,unpubl. info.)). During our visit 250 pratincoles isedby The AustralasianWader StudiesGroup) while it was were caughtand it waspossible to feel what appearedto be basedat Eighty Mile Beach(Anna PlainsStation), Western the bodiesof locustsin manyof the birds' crops.Flying ter- Australia(19 ø 20'S, 121ø 26'E, Fig. 1) from 2 to 9 February miteswere also common as were non-flying, young (hopper) 2004. locustsand grasshoppers. As we approachedAnna Plains stationon 2 February,it All pratincole speciesare largely crepuscularfeeders was immediatelyapparent that very largenumbers of Orien- (McNeil et al. 1992).However, the lengthof twilightin the tal Pratincoleswere usingthe area.We madesample counts tropicsis soshort that it mustbe necessaryfor themto choose and studied their daily behaviour. From dawn they fed betweenextending their feedinginto daylightor into dark- extensivelyover the grazinggrassland of the stationas well nessor possiblyboth. PresumablyOriental Pratincolesin as further inland above the bush, at least as far as the Great Australiachoose daylight because on at leastsome days at NorthernHighway, 20 km from the coast.As the tempera- AnnaPlains large numbers fed throughoutthe morning until ture increasedeach morning (the weatherwas relatively at leastmidday returning to feed againfor aboutthree hours settled,calm and sunnythroughout), the birds gradually before dusk.Possibly some continued to feed for a while movedout to the coastwhere they collectedin hugeaggre- afterdusk because eight birds were caught in mist-netswhen gations on the upper mudflats and the beach. During the it wasquite dark, though as it wasonly threedays before full period of our observations,high water was in the middle of moon, there would have been a considerable amount of the day and,as the tide rose,the pratincolesmoved onto the moonlight.The very similarCollared Pratincole G. pratin- sandybeach. The birdsremained on the beachor the upper cola hasbeen recorded as feeding on moonlitnights (Urban mudflats,long afterthe tide had goneout anddid not depart e! al. 1986). to feed inlanduntil 1500-1600h. They then fed until dusk Between1130h and 1230hon 5 February,two of us (CM beforegoing to rooston the grassyplains. & CH) carriedout a quick surveyof pratincolesalong the There were also smaller numbers of Oriental Plovers northernmost62 km of EightyMile Beach.In the southern- Charadriusveredus (a few thousandin total) behavingin most 1 km of this section46,000 were counted.To the north, muchthe samemanner - feedingon the plainsin the morn- the densitywas considered to be aroundhalf thisfigure. The ing and late afternoonand roosting on the beachin the heat coastto the southwas not surveyed,but from a distance,the of the day. densityappeared to be similar to the stretchthat had been There was no standingwater on the plainsexcept for a counted.Extrapolating from theseobservations suggested a few puddlesduring the first day or so from light rain which populationfor the wholeof Eighty Mile Beachof between fell on 30 January.However, there had been rather more rain 2.0 million and4.6 million. Clearly, with a previouslyesti- • Bulletin103April2004 26 Sitters et aL: Numbers of Oriental Pratincoles in NW Australia 27 the Anna Plains entrance southward. The third vehicle cov- CapeBossu! eredthe next 35 km to the south.Therefore the total length • e - •Frazier Downs of beach counted was 86 km. Detailed counts were used as INDIANOCEAN / / the basis for estimatingnumbers in large flocks. In each vehicle, a consensuswas reachedbetween the countersas to the figure that shouldbe recorded. F•she•e'hansCamp EightyMile Beach 70kin Aerial count on 7 February 2004 High waterwas at 1147 h andthe counttook placeas the tide was falling between1230h and 1430h.The aircraftwas a 4- seatCessna with highwings that allowedgood visibility. The .,• • .......... countwas carriedout by PC, HS and BE who had all taken • Hedland• "-. part in the previousday's groundcount and were amongthe mostexperienced wader counters on the expedition.The air- Fig, 1. Eighty Mile Beach, NW Australia, showing distances from craft flew from the Anna Plains entrance south to Cape Cape Missiessy south to Cape Keraudren. Keraudrenand then returnednorth to Cape Missiessy.One countwas carriedout by PC (who sat on the left behindthe matedflyway populationof only 75,000, a full and accurate pilot) on the flight southand a duplicatecount was doneby countwas highly desirable. It wastherefore arranged to carry HS (front right seat)on the flight north. BE (rear right seat) out a detailed groundcount of the northernmost71 km of acted as recorder and cross-checked the counts whenever EightyMile Beachand the first 15 km of the bay to the north possible.The beachwas counted in sections,divided by eas- on 6 Februaryand an aerial countof the whole beachon 7 ily recognisablefeatures, allowing us to comparethe num- February. In responseto the plea by Brouwer et al. (2003) bers in each sectionbetween the two counts.However, some for good documentationof important counts, we explain of the featuresused (such as a whale skull) were not suchas exactlyhow thesewere carded out. to enable their location to be identified on a map. One of thesefeatures was the restof the membersof the expedition METHODS who were bandingwaders having made a cannonnet catch at 1200h,shortly before the flight. They madeobservations Ground count on 6 February 2004 that helpedus interpretthe resultsof the count. In both directions, the aircraft flew about 60 m above the High waterwas at 1120hand the countwas carried out asthe water's edgeand at about 150 kph. tide was droppingbetween 1400h and 1500h. Countswere done by 3-6 experiencedwader countersin each of three RESULTS 4WD vehiclesdriven alongthe beach.One vehicle covered the northernmost20 km of Eighty Mile Beach, from the The ground count revealed 818,000 Oriental Pratincoles Anna Plains entranceroad to Cape Missiessy as well as along86 km of beachon 6 February,whereas the southward 15 km of the bay to the northin the directionof CapeBossut and northward aerial countson 7 February recorded2.45 (Fig. 1). The secondvehicle covered a 16 km sectionfrom million and2.88 million respectivelyover 235 km (Table 1). Table 1. Counts of Oriental Pratincolesat Eighty Mile Beach, NW Australia, on 6 and 7 February 2004. The ground count on 6 February relates to the northernmost71 km of Eighty Mile Beach plus 15 km further north towards Cape Bossut. The aerial counts relate to the whole 220 km of Eighty Mile Beach and the same extension to the north - a total distance of 235 km. Arrows show the direction of the aerial flights. Ground count 1400-1500h Southward aerial count Northward aerial count on 6 Feb 1230-1330h on 7 Feb 1330-1430h on 7 Feb (counter: P. Collins) (counter: H. Sitters) Cape Bossutto Cape Missiessy 35,000 Finish 25,000 Cape Missiessyto Anna Plains entrance 41,000 t 48,00025,000 a 48,000 Anna Plains entranceto Fisherroans'camp 197,000 Start 270,000 102,000 Fisherroans'camp to bandingteam 65,000 26,000 Bandingteam to whale skull 480,000b 35,000 16,000 Whale skull to Mandora 2nd creek 1,751,000 2,516,000 Mandora 2nd creek to Mandora 3rd creek 33,000 20,000 Mandora 3rd creek to Mandora campsite 121,000 48,000 • 57,000;tart Mandora campsiteto Cape Keraudren Finish 108,000 75,000 Totals 818,000 (partial count) 2,448,000• 2,876,000 The northernmostcounting sections from CapeBossut to Anna Plainsentrance were only countedduring the northwardflight,