Corella 2003, 27(3): 81-€4

I-ARGEMORTALITY OF SHORT-TAILEDSHEARWATERS PUffiNUS tCNUirOStriSIN AUSTRALIAN AND NEWZEALAND SEAS IN OCTOBER2OOO

IRYNEJSKIRA

NatureConservation Branch, Depa mentof PrimarytDdusaies, Water and Environment' PO Box 44, Hobar!, 7001

Reeived: 1l February2002

A majormortality of Short-tailedShearwaters Puffinus tenuirosttis occurred in Octoberand November2000 as the biids returnsdto thek breedingcoionies in southernAustralia. Beachwashed birds were found along the eastcoast of ,from 4OO kilometres no(h ol Brisbaneto southernTasmania, and westto NewZealand. Autopsiesshow€d that the most iikelycause oi deathwas starvation.This lack of food was probauydue to large-scalevariation in watercurrents as the majormortality coincided with unusuallywarm east coasl Australian se; surhcetemperatures. Such large mortalities are naturalirregular occurrences among Short-tailed Sh€arwaters, but theirimpact on the populationis difficultto gauge.

INTRODUCTION RESULTS The Short-tailed Shearwater Puffinus tenuirostris ts Beach counts regardedas Australia's most abundantseabird (Serventy et al. 1971). It is a trans-migratory seabird that only breeds New South Wales in southernAustralia and migrates to the far Northern First casualties were reported in early October. On 1l Hemisphere in the ausfal winter. The shearwatersretum October 2000, 80 beachwashedbirds were counted along a to Australian waters from September, and it is not 500 metre stretch of beach near EurunderieLagoon, Myall uncommon to see carcassesbeachwashed (Reid 1999). On Lakes. Live birds in an emaciatedcondition were still being occasion,large mortalities occur that have invoked attention washed ashoreduring the count. Also on the same day, 60 sincefirst reportedin l85l (North 1898;Hindwood 1940, shearwaterswere tbund on the beach at Mungo Brush, i949; Iredale 1930; Serventy 1941, 1,943,1967). oppositeBroughton Island, (Ian McAllan, pers.comm.). The In October and November 2000, dead birds were found previous day there were no shearwatersat either location. from 400 kilometres north of Brisbane to southern The major mortality probably occurredon the central and Tasmania, and west to New Zealand. In this paper I north coasts (Table l). The highest number of dead birds describe this large mortality, look at possible underlying was recorded near South West Rocks north of Port causes and assessthe impacts on the breeding of Short- Macquarie, with 1820 birds per kilometre over 4.5 tailed Shearwaters. kilometres on 25 October 2000, which was the largest mortality of shearwatersalong that section of coast for at METHODS least ten years (Ken Shingleton,pers. comm.). South of Countsof beachwashedShort tailed Shearwaters were made alotrs. Sydney to BatemansBay, the count was 64 birds per Ausrrahan maroland,Tasmanicn and Ne\r Zealand beaches.I small kilometre over 1.5 kilometres near Bawley Point south of sample of birds was also collectcd for autopsy in Victoria. Ulladulla, and 74 birds per kilometre over 2 kilometres of beach Depot Beach, also (Lindsay The percentage of burrows occupied by a shearwater in mid at south of Ulladulla and December compared to lhe total counted, or burrow occupancy, was JaniceSmith, pels.comm.). compared between years. Burrow occupancy has b€en modtored since 1997 as part of the long-term Short-tailed Shearwater management Victoria programme in Tasmania (Skira 1996) on several colonies io the In Mctoria it was reported that '100s of short-tailed Fumeaux Group (40"S, 148"E, situated off north,east Tasmania). One of the counts is in December duriog the incubarion period. Egg laying shearwaters washed up on the eastern Port Phillip Bay in Short-tailed Shearwaters is synchrooor.tsbetween years and occurs beaches'(Ruth Connell, pers. comm.). between 20 November and 3 December (Serventy 1963). In cach colony, counls follow the melhods described in Skira and Wapsrra (1980) and Tasmania are done along thrce 100 x 2 metres lransects on the same transect lin€s as in previous years. Breeding data was also garhered from the small Large mortalities were noticed approximately one week Shon-hiled Shearwater colony (up to 100 pairs) otr Fisher Island in the after that in New South Wales. Beach counts were spread Fumeaux Group, as part of a study that began in 1947 (Scrvcnry 1977). across Tasmania and gave a rate as high as 420 birds per To study the oceanographicinfluences on shearwaters,east Australian kilometre (Table 2). Similar large mortalities occurred on current sea surface temperature data were obtained fmm the Australian beacheson the west coast (Ocean Beach) as for the east Oceanographic Data Centre websile (www.aodc.gov.au). coast (Clifton Beach).

81 SkTa: Mortality of Short{ailed Shearwaters Corella27(3)

TABLE T New Zealand Coun6 of beachwashedShorltailed Shearwaters in northemNew South Wales,October to November 2000 (NarelleSwanson pers. "o.-.j. ii Many dead birds were found spread along areasof New Sawtellr2 TuckersRock; 3 Boambee; 4 North Beach:5_Bonville; 6-Cofis Zealand'scoast. Fishers saw birds dead at sea,and the ones Jetty;7 Sturu Pointi 8 Mooneei9 Emerald; 10 WoolgootgaBeach; li on beacheswere very emaciated poor WoolgoolgaHeadland). and in condition (Henrik Moller. pers. comm.). The toral counr of Beach Number/km beachwashedbirds reported for all the beacheswalked was almost I 000, with 523 20 Ocl I 3.0 I 800 600 of them from Invercarsill and the bottom 21 Ocl 2 0.2 r00 500 end of the Sourh lsland, and the remainderlrom 3l Oct 3 6.0 2 000 333 all aroundthe North Island(Phil Rhodes,pers. comm.). I Nov 4 8.0 I 600 200 Burrow occupancy 5 Nov 5 0.05 300-500 15 Nov 6 1.0 200 ,7 200 The percentage of burrows occupied comoared to the 15 Nov 0.15 300-500 total. in December2000, varied betweencoionies bv as 16 Nov 8 3.0 430 t43 much as 20 per cent (Table 3). Variation also occuned 16 Nov 9 1.0 168 168 between years. For example, on Big Green and East 17 Nov IO 3.0 454 l5l Kangaroo Islands, in December 2000, burrow occuDancv l? Nov ll 1.0 160 t60 was down by 20 per cent comparedto December1999. These two islands are within 5 kilometres of each other. On all colonies monitored, burrow occupancy was greater TABLE 2 in December 2001, one year after the major mortality. Countsof b€achwashedSho(-tailed Shearwaters in Tasmania,October to Novcmbrr2000. rl WaubsBay. 2 EagtehawkNeck: .] Richirdson,4 TABLE 3 S\ anwick:5Callen s, o Lrghrhouse:? Bellerive: g Cliftonl s E3eteha\ak Percentageof Short-tailedShearwater burrows occupied during the Neck:I Mirrion:l0 Roaring:ll SrfelyCove: 12 CremornellJ Hopc: mcubationperiod in Decemb€roo somecolooies in theFumeaux C;oup. 14 SevenMilei 15 Ocean;16 Carlton; 17 Cressy;18 Lufra; 19 pirares Bay.20 himroseSand!: 2t RoariDS: 22 SlopingMain:21 Baylelsl 24 Island 199',7 1998 1999 2000 2001 Coonellys Marsh:25 SusanBay; 26 Taroona;2? Fortescu€). GreatDog 57.',| 56.8 6l.3 54.5 Dale Beach Little Dog Y 65.4 50.2 ',73.3 Leogrh tkm' Number found Number/km '71.3 60.8 Little Green 46.6 58.9 12.a 18Oct I '70.3 0.5 20 40 Big Creen 661 6't.l 48.0 78.0 20 Oct 2 3.0 230 78 East Kangaroo 64.5 62.4 65.0 4s.0 80.4 20 Oct 3 2.0 t20 60 Fisher 55.6 45.0 58.0 40.8 6',7.2 20 Ocl 4 60 40 22 Oct 5 2.0 l 55 Fisher Islantl coLony 24 Oct 1.0 50 50 25 Ocr 'l 1.0 52 52 The percentageof burrows occupiedcompared to the total 26 Oct 8 2.0 507 259 during incubation in December 2000 was 4l per cent 26 Oct 2 2.0 202 l0l comparedto 58 per cent in 1999-2000,45 pei cenr in 26 Oct 9 4.O 167 1998-1999.50per cenrin 1997-1998and 48 per cenl in 26 Oct l0 t.0 8l 8l 1996-1997. Another measure of the effect of mortalitv is 26 Oct 1l I 9 9 recruitmentinro a breedingpopulation. Data from Fiiher 2'l Ocl 8 2.O 260 I30 Island show that 10.1 per cent of the shearwaters 2l Ocl t2 1.0 180 180 breedingin 2000-2001had neverbeen previously 21 Ocl l3 5.0 4',70 94 recordedon Fiiier Island (Table4). 2'7 Ocr 10.5 3 350 319 In the 20012U)2 breedingseason, 16.4 per cent 29 Ocl l5 20.o 200 l0 of the shearwaterswere new birds to the island.and since 29 Ocr t6 250 100 the 1982-.1983breeding season, mean annualrecruitment of 30 Ocr t6 2.5 250 100 new breedingbirds has been 6.8 a 1.7 per cent (j2SE). 30 Oct t1 0.5 15 30 30 Oct l8 I 200 200 30 Ocl l9 2.0 50 25 TABLE 4 Annualpercenlage 30 Oct 20 L5 t20 80 recruitmentof newbreeding Short tailed Shearwarers intothe Fisher Island populatioo from December 1982 to 30 Ocl 2l 1.0 20 20 December2001. 30 Oct 22 3.0 100 34 New Breeding New Breedinq I Nov 23 3.0 300 100 Year Brrds(per cep year Birds{per ceni) I Nov 5 0.5 210 420 2001 16.4 1991 I Nov 24 1.0 14 74 2000 l0 I 1990 't.'7 2 Nov 25 1.0 38 38 )999 9.0 1989 8.5 3 Nov 26 1.0 3 3 I998 7.2 1988 9.9 7 Nov 27 0.5 59 118 t99',7 5.8 198? 13.4 ll Nov 2 2.0 2l 1996 1.4 1986 7.3 t995 3_8 ll Nov l0 4.0 46 t2 r985 5.7 1994 4.1 1984 0.9 ll Nov 22 1.0 89 89 1993 1983 12Nov 27 0.5 8.0 6 1992 2.2 t982 September,2003 Sklra. Mortalitvot Short-tailedShearwaters

Autopsy reported was 8.07 Short-tailed Shearwatersper kilomete with the highest total count of 864 birds in 1986 In October 2000, five short-tailed shearwaters were (Powleslandand Pickard 1992).The 2000 mortality appears (K. Harrigan, School collected in Victoria for examination to have approachedthe mortality rate of 1986. of VeterinaryScience, Melbourne University, pers. comm.). All birds were in emaciatedcondition. Four of the birds were It is not known which age groups were most affected malesweighing 320 grams,380 grams,400grams and 410 Short-tailed Shearwaterscan be aged into broad categories grams respectively,while the single female weighed345 (Sugimori et at. 1985), but none were. The major mortality grams.The proventriculusof two birds containeda pilchard- did affect breeding considerably.However, it is difficult to like fish, some 12 centimetresin length. The gizzard part proportion the cause, pa icularly when similar, irregular of the birds containedpieces of gravel (4 birds), plastic (2), large mortalities occurr when Short-tailed Shearwatersare and one bird had a moderatelylarge number of cestodeeggs. in the Northern Hemisphere part of their migration (Baduini et al. 1999). Nevertheless,the vadation in East Atrttrclian current sed surface tenperatures percentage of burows occupied between years when no major mortality was recorded was much less than The large mortality of October 2000 coincided with compared with December 2000. The lower occupancy on unusually warm sea surface temperaturesin the east Fisher Island compared to other colonies may be a direct Australian cufrent. Sea surface temperaturgtbr 16 August result of regular human disturbance by researchers.Adult 2000 shows an intrusion of water warmer than 22'C at shearwatersare handled on Fisher Island to read band 3l'S, 154"E, extending down the coast of New South numbers, sex and to be banded as required. On other Wales.This warm water was then replaced by cooler water colonies, no birds are handled as burrow occupancyis until its reappearanceon 19 September2000. It then gauged by checking a burrow with a hand or a stick. On conlinuedto extendin size.and rose in temperalureto Fisher Island, the large proportion of new breeding birds morethan 25"C pushingout coolerwater of lessthan 19"C in the total breedingpopulation for the island in 2001, from eastern . In contrast, sea surface data for 2000 and in 1987, suggeststhat major mortality could be 1998 and 1999 show cold water of lessthan l9'C as the a mechanism that bdngs about gene flow between main water bodies along the New South Wales coast up shearwatercolonies. Austin et al. (1994) and Bradley et al. to mid-November. In 1999 water warmer than 22"C first (1999) describehow gene flow in short-tailedshearwater appearedon 13 October 1999,but did not displacewater colonies occurs through rare, large-scalemovements of of less than 19'C along much of the New South Wales individuals. Despite being strongly philopatric (Serventye/ coast mid-December. until In 1998, a small intrusionof al. 1989), populations of Short-tailed Shearwatersrecover water of more than 22'C remained from 16 to 30 quickly from largemortalities. September 1998 then reappearedon 21 October to remain fbr the restof the shearwaterbreeding season. As in 1999, Autopsies revealed that birds were emaciated and it did not displacecooler water of less than l9'C along dehydrated. Similar results were found by Taroonga Zoo the New SouthWales coast until mid-November1998. veterinarianson autopsiesof eight Short-tailedShearwaters (KaIIie Rose, Australian Registry of Wildlife Health at DISCUSSION TarongaZoo, pers. comrn.). The most likely causeof death was staryation(North 1898;Hindwood 1949;Gibson and BeachwashedShort-tailed Shearwaters are found along Sefton 1955;Hindwood and McGill 1955;Serventy er al. Tasmanianbeaches as early as the beginning of September l97l; Green and Scarborough1985) and that intestinal (Green and Scarborough1985). According to Serventyet parasitismcontributed only minimally to their debilitation al. (1971), large mortalitiesrarely extend into Tasmania and subsequentdeath. Hindwood (1940) and Serventy despiteit containing8l per cent of the population(Skira (1943) speculatedthat this lack of food was due to large- et al. 1996), and no large mortalities on the scale of scale variation in hydrographic factors, particularly water October 2000 have been noted since at least 1975.The rate currents.The large mortality in October 2000 coincided of 420 Short-tailedShearwaters per kilometre compares with unusually warm east coast Australian sea surface with an annual mortality rate of 5.3-7.0 Short-tailed temperatures.The main diet of shearwatersin September Shearwatersper kilometre basedon counts from 1992 and October is primarily the euphausiid Nyctiplnnes l99E (Reid 1999).There are no countsavailable for years {zr.r.r/ralir(Montague et al. 1986',Skira 1986).The optimal previous to 1992. Large numbers were also washed up in temperaturerange tbr this euphausiidspecies is from 12 New SouthWales, although the mortalitysouth of Sydney to l8'C, and it is most abundantfrom July to September to BatemansBay was only marginally greater than in (Blackburn 1980). N. castralls moves diurnally and is previousyears (Lindsay and JaniceSmith pers. comm.). restrictedto the continentalshelf (Blackburn1980). There Other shearwaterspecies were also alfected. Narelle is evidencethal numbers of thisspecies fluctuate from year Swanson (pers. comm.) observed that Wedge-tailed to year,because its distributionis tied to watermasses and ShearwatersPuffinus pacrficus, returned later to the major current systems.In July 2000 water warmer than breeding colony on Muttonbird Island near Coffs Harbour, l8'C was alreadypresent along the eastAustralian coast and were approximately 20-30 grams lighter compared to and extendingover the continentalshelf. It persistedfor other years. In New Zealand, Short-tailed Shearwatersare the remainder of the year. If Short-tailed Shearwatersare not commonly encountered(Veitch 1980;Powlesland and heavily dependenton krill for food immediatelyon rheir Pickard 1992).The mortality rate measuredas birds per return to Australian seas, warmer currents which are kilometrewls not availablefor the 2000 morralirv.bur unproductivefor krill and result in food shortages,are most durints 1943 I988. lhe mean number of shearwarers likely the causeof large mortalities(Skira 1986). Sklra. Mortatityol Short-taitedShearwaters Cotella 27 \3) impact of large mortaliries ^.The on Short_tailed Hindwood, K. A. (1949). Sea,bird mortality. Aust. Museun Mag. March Shearwaterpopularions is difficult ro gaugewithout having 30 329-332. Hiodwood. accessto long-term data sets.More than fifty years of dati K. A- and Mcciu, A. R. (1955). Sea-bird morrajity in coasral New Sourh Wales during are available on Shorrtailed Shearwaterson Fisher Island, July, 1954. Enu SSt 148_156. 329_332. Iredale, T. (1930)- Aviar sea toll. Arrrr Zaol. 6t 1tZ-114, pt^te xlji. but Ihe small breedingpopulation makes ir difficult to Montague, T. L., Cullen. J. M. and Firzherbe(, K. (1986). The diet of determinewhether puffinus large-scaleclimare influencesor other the short-tailed shearwater tenuirostris dUtring its breeding factors are influencing the population. Nevertheless,such scason. tm, E6: 20'l-2t3. Murphy, R. (1936). 'Oceanic oata serve aS a Starting point. Seabirds are imDortant C. Birds of South America.. (Macmillan and American Museum of Natural york.) indicatorsof changesin global climare. History: New The occurrinceoI \orth, A. J. r1808) tn Handbook ot Sydney warmer water in aoA r'he Counry of 2000 may be a result of the El_Nino Cumberland.' (Ed. W M. Hamler). pp. lt4-n5. (Ausrral;sian So^uthernOscillation (ENSO). Murphy (1936) and Duffy Association for the Advancement of Science.) Powlesland, (1989) both describedthe effects of ENSO on seabiri R. c. and Pickard. C. R. (1992). Seabirds found dead or New Zealand beaches in 1998, pu.ffinus populations with long-term data sets beins the crucial and a review of species recoveries, 1943 Lo 1988. Nototnis 39.2i46. answerto the problemsof seabirdpopulation flucruations. Reid, T. (1999). Seabirds found dead on Auslratian beaches in 1995 and 1996. Austalasian Seabid Croup Newsletter 34t 1c.16. ACKNOWLEDGMENTS Servenry,D. L. (1941).Mating in petreis.Enr 4t: 88_89. Serveniy, D. L. (1943). Sea birds and fisheries. The problem of multon_ I rhank Trm Rerd of the AuslralasianSeabird Croup for Drovidinq bird deaths. Fishetier Newsleuer 2(Z)t lZ-15. access to lhe data on beachwashed seabirds. Ranger5 oi LheTasmaniai Serventy, D. L. (1963). Egg laying timetable of rhe Slender_billed Parksand Wildtife Servrccprovrded counls from severalbcacheJ Rulh Shearwatet PxJtrnrr tenuirostris. pro(:. XIII Intemationa! (onnell.in Ornithol Victoria. Dumo Munay. Nick Klornp, Lindray atrd JaDice Congrcss,338-343. Smilh. Ken Shioglton.lan McAllan and NarelleSwanson rn New South Serventy.D L. { lqbT). Aspect! of the populationecology of lhe Shoa- Wales; and Phil Rhodes in New Zealand provided information on their rarled 5hear$arer Pullinur kruitostrit. pro.. XMntcmarionat resPecuve reglons, Ornithol. Congrcss, 165-190. Serventy,D. L. (1977). Seabird Islands. No.49. Fisher Island. Tasmania. REFERENCES Corella ll 6042 ,The Serventy, D. L., Scrventy, V and Warham. J. (1971). Handbook Aus! , J- J., White, R. W. c. and Ovenden,J. R. (1994). poputarion, ofAustralian Sea-birds.'(A.H. and A. W Reed:Svdnev.) genetc strucrure philopatric, of a colonially nesting seabi.d, tte Servenry.D. L.. Cuno. B. M.. Skird. L J.. Brrdley. i S.-andwoo er, Shorttailed .tg. Shearwater (prfnlr tenuirustfis.).Auk 117 jO R. D (1989)- Fledgling translocarion and phiiopahy in a seabird. Baduini,C. L., Hyrenbach,K. D. and Hunr, c. L. 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