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State of the Marine Environment Report for Australia: The Marine Environment - Technical Annex: 1

Compiled by Leon P. Zann
Great Barrier Reef Marine Park Authority, Townsville Queensland

Ocean Rescue 2000 Program
Department of the Environment, Sport and Territories, Canberra, 1995

ISBN 0 642 17399 0

The status of Australia's seabirds

G.J.B. Ross1, A.A. Burbidge2, N. Brothers3, P. Canty4, P. Dann5, P.J. Fuller2, K.R. Kerry6, F.I. Norman7, P.W. Menkhorst7, D. Pemberton3, G. Shaughnessy1, P. D. Shaughnessy8, G. C. Smith9, T. Stokes10 & J. Tranter11

  1. Australian Nature Conservation Agency, GPO Box 636, Canberra ACT 2601
  2. Department of Conservation and Land Management, WA Wildlife Research Centre, PO Box 51, Wanneroo SA 5067 3
  3. Department of Parks, Wildlife and Heritage, GPO Box 44A, Hobart Tas 7001
  4. Biological Conservation Branch, Department of Environment and Land Management, PO Box 3034, Norwood SA 5067
  5. Penguin Reserve Committee of Management, PO Box 403, Cowes Vic 3922
  6. Australian Antarctic Division, Channel Highway, Kingston Tas 7050
  7. Flora and Fauna Branch, Department of Conservation and Natural Resources, PO Box 137, Heidelberg Vic 3084
  8. CSIRO Division of Wildlife and Ecology, PO Box 84, Lyneham ACT 2602
  9. Fauna Conservation and Ecology, Department of Primary Industry Forestry Service, PO Box 635, Indooroopilly Qld 4068
  10. Great Barrier Reef Marine Park Authority, PO Box 1379, Townsville, Qld 4810
  11. Government Conservator, Australian National Conservation Agency, Cocos (Keeling) Islands, Indian Ocean, WA 6799

Introduction

The seabird fauna of Australia and its external territories is diverse and comprises 110 species representing 12 families (Serventy, Serventy & Warham 1971, Marchant & Higgins 1990, Selkirk, Seppelt & Selkirk 1990, Woehler 1991, Woehler & Johnstone 1991, Woehler, Hodges & Watts 1991). Of these, 76 species (69%) breed, and many spend their whole lives in one or more parts of the region. A further 34 species are regular or occasional visitors to the region where they feed in the non-breeding season. The species diversity of the Australian region is intermediate between that of the North Pacific Ocean (62% breeding, total of 154 species in 13 families) and the North Atlantic Ocean (68% breeding, 81 species in 12 families) (Harrison 1983).

Although the biology of many Australian seabird species is better known than that of many terrestrial birds and other marine organisms, information on population levels and status for most species is poor. Non-sustainable exploitation by man of breeding seabirds largely has ceased, but a variety of other anthropogenic effects is putting pressure on some breeding populations around Australia.

Population estimates for each breeding species assessed against various human impacts, provide a measure of the status of Australian seabirds. The value of seabird populations for monitoring

purposes, and the research needed to implement effective monitoring, are discussed in this report.

Value and usage

Australian seabird breeding colonies have provided a valuable and fairly predictable food source for indigenous communities, mariners, explorers and entrepreneurs for centuries.

Seabirds breeding on islands close to shore were probably an important food source to coastal Aboriginal communities. The impact of their harvesting on seabird populations is unknown as few records remain. Shearwater chicks from Mutton Bird Island, New South Wales were eaten in initiation ceremonies (Swanson 1976). Serventy, Serventy and Warham (1971) suggested that some Western Australian islands suited to seabird habitation yet presently unoccupied by them, may have been overexploited by Aborigines in the past. South-west Tasmanian Aborigines valued seabirds highly and travelled at least 15 km on paperbark rafts to Maatsuyker Island to hunt seals and nesting short-tailed shearwaters (Flood 1989).

In Torres Strait, islanders from Murray, Darnley and Stephens islands continue a traditional harvest of booby chicks and eggs on Bramble Cay and several smaller islands, their harvest facilitated by modern small craft (Elvish & Walker 1991). Such harvests occurred previously on Raine Island (Serventy, Serventy & Warham 1971). Torres Strait Islanders also harvest a large proportion of eggs from Kusamet Island every year. Adults of several bird species are collected for feathers to be used in ceremonies (Johannes 1991).

The impact of intermittent harvesting of seabirds is impossible to estimate. Harvesting was initiated by South-east Asian trepang fishers and followed by European mariners, pearling crews and more recently Indonesian and Japanese fishers. However, the impact of harvesting is likely to be less than that of sealers on Australian and subantarctic islands, or resident labourers on islands during commercial guano collection. Until recently, the practice of killing seabirds for crayfish bait was prevalent ( Serventy & Warham 1971), although less so in Western Australia. Little penguins were preferred, and black-faced shags, short-tailed shearwaters and Australasian gannets were also used widely. The effects of such collection were seen most strikingly in the decline of the Cat Island gannetry in Bass Strait from 2500-5000 pairs to fewer than seven pairs between 1908 and 1977 (Warham & Serventy 1978).

Up to 150 000 king and royal penguins a year were boiled down for oil on Macquarie Island between 1890 and 1920 (Cumpston 1968). The penguins reputedly provided a meagre return of about 20 per year.

Muttonbirding encompasses the traditional and sustainable commercial harvest of short-tailed shearwaters. It is conducted on seven Bass Strait islands largely by Tasmanian Aborigines, under management of the Tasmanian Government. The current harvest of 400 000 chicks a year is valued at $330 000 to the harvesters and retails at $ 3.2 million (Beaton 1990). The impact of illegal muttonbirding on populations on several Tasmanian islands is uncertain, or limited on Victorian islands.

Providence petrels saved the fledgling Norfolk Island settlement from starvation in 1790, when some 180 000 petrels were eaten over a three-month period (Hicks 1988). Norfolk Islanders have a traditional harvest of sooty tern eggs from nearby Phillip Island (Jurd 1989). Cocos Island Malays have harvested large numbers of red-footed boobies from North Keeling Island, an annual take estimated at 3000-10 000 birds (J. Hicks, pers. comm.). Following a cyclone, a moratorium was placed on harvesting in 1989 to allow the colony to recover. In contravention of Australian legislation enacted in 1992 however, illegal harvesting of red-footed boobies and frigatebirds around Cocos (Keeling) Atoll continues.

Tourism potential of seabird colonies is limited by the problem of constraining human disturbance and access to most colonies on offshore islands. The successful 'Penguin Parade', established on Phillip Island (Victoria) in 1928, presently draws nearly 500 000 visitors annually. Although measures to reduce disturbance have been successful, the colony on the island is in decline. The decline is apparently the result of increased adult mortality at sea and on land, where penguins are killed primarily by foxes, dogs and motor vehicles (Dann 1992). In New South Wales, penguins form the basis of a new tourist initiative in Jervis Bay and on Montague Island. Carefully-managed tours by charter boat to the Houtman Abrolhos (Western Australia) are increasing, and an industry developing around Michaelmas Cay, off Cairns (Queensland), is being encouraged to regulate itself to ensure protection of the seabird colonies. Numerous islands - including several seabird islands in the Capricorn/Bunker group of the southern Great Barrier Reef - form the focus of tourist activities.

Description and status

Australia

In broad terms, the tropical and southern ocean elements of the seabird fauna reflect Australia's geographical location (Table 1). A few tropical species have adapted to a broader range of environmental conditions. Almost all tropical species extend south to about Fraser Island (25oS) on the east coast. The influence of the warm Leeuwin Current enables tropical roseate terns, bridled terns and red-tailed tropicbirds to breed as far south as 32-34oS on the west coast (Dunlop & Wooller 1990).

Estimates of the number of breeding pairs of seabirds along the Australian coast (Table 1) have been compiled from published population data for 294 islands surveyed and a few coastal sites as well as unpublished data from several sources. Excluded were gull-billed terns, white-winged terns and whiskered terns, great cormorants and little black cormorants, because they breed inland and generally feed infrequently in marine environments.

Region 1 2 3 4 5 6 7 8 9 10 11
Total
 
                        Min Max
Little Penguin [C] 800-1200         13.3- 23.4-29.5e3 2489-2748 243-447 85.6-151.8e3 23.3-40.6e3 149130 249900
Shy Albatross [C]                   2700-3300 4200-5200 6900 8500
Great-winged Petrel [C]                 33.1-84.1e3     33050 84100
Herald Petrel [T]         3             3 3
Black-winged Petrel [T]           3           3 3
Gould's Petrel [T]           250-500           250 500
Fairy Prion [C]             1359-1639     71.8-118.7e3 98.2-156.2e4 1055060 1682000
Wedge-tailed Shearwater [T] 10.7-10.9e5 30.1-60.3e3     15.1-15.3e4 43.3-53.3e3           1301150 1344400
Flesh-footed Shearwater [C]               br 10.5-31.1e4     104540 310600
Sooty Shearwater [C]           296-510         3-700 300 1210
Short-tailed Shearwater [C]           26.6-27.1e3 1.96e6 495300 3330-3200 7.8-10.1e6 2.5-3.4e6 12787070 16059700
Little Shearwater [C] 24.0-54.4e3               3060-7140     27060 61600
White-faced Storm-petrel [C] 8399-19370         10.6-12.2e3 32600 143770 9620-21020 160600 5000-8000 370180 396600
Common Diving-petrel [C]             20+     83.2-116.0e3 46.0-68.0e3 127220 184000
Australasian Pelican [I]   428-988 <200   140-220   177   30-70 47   1030 1680
Australasian Gannet [C]             3140+     1000-1500 1406-1500 5540 6140
Masked Booby [T]   590-610   399-614 2763-3046             3750 4270
Red-footed Booby [T]   13   1290-4896 78             1380 4990
Brown Booby [T]   3.4-3.8e4 16.2-22.7e3 722 9001-12418             59940 73900
Pied Cormorant [T] 3400-4000 6554-12594 130   90 500 138 1465-1645       13080 19120
Little Pied Cormorant [I] 10       7 100-150   25-30       140 200
Black-faced Cormorant [C] 21         50-120 90+ 4280-4420 46 2700 700 7740 8110
Great Frigatebird [T]   3-7 1 1581 22             1610 1610
Lesser Frigatebird [T]   9530-10100 4919 2253-2265 2160-2347             18680 19430
Masked Booby [T]   590-610     399-614 2763-3046           3750 4270
Red-footed Booby [T]   13   1290-4896 78             1380 4990
Brown Booby [T]   3.4-3.8e4 16.2-22.7e3 722 9001-12418             59940 73900
Pied Cormorant [T] 3400-4000 6554-12594 130   90 500 138 1465-1645       13080 19120
Little Pied Cormorant [I] 10         100-150   725-30       140 200
Black-faced Cormorant [C] 21         50-120 90+ 4280-4420 46 2700 700 7740 8110
Great Frigatebird [T]   3-7 1 1581 22             1610 1610
Lesser Frigatebird [T]   9530-10100 4919 2253-2265 2160-2347             18680 19430
White-tailed Tropicbird [T]   0-2                   2 2
Silver Gull [I] 6480-14967 1150-2190 129   398-504 61.1-66.6e3 41.8-51.5e3 12.6-13.0e3 3400-7550 4200 2100 133890 163620
Pacific Gull [C] 74-84 14         437 80-121 7 1100 185 1900 1950
Kelp Gull [C]           11 3       300 315 315
Caspian Tern [I] 141 767-927     7-9   89-94 83-201 14 41 13 1160 1410
Roseate Tern [T] 4310-5060 300-760 990   1618-6560             7220 13370
White-fronted Tern [C]                   44   44 44
Black-naped Tern [T]         1706-2076             1710 2080
Sooty Tern [T] 28.3-33.8e4 10.0-50.0e3     35.8-76.5e3             328760 383750
Bridled Tern [T] 10.1-44.0e3 3080-4080     6882-9738       1     20040 57870
Little Tern [T]     11   56 80-87 400 6   10   560 570
Fairy Tern [I] 1512-1962 375-454         200+ 100-130 135 109   2420 2990
Crested Tern [I] 1380-1780 5870-13770 13.0-15.0e3   24.1-29.2e3 11.7-12.7e3 2705-3355 4750-5830 3630-8430 6900 400 74350 89940
Lesser Crested Tern [T]   2-500 35   4676-7634             4710 8170
Common Noddy [T] 116500 13.6-35.1e3     44.4-62.5e3             174480 214130
Lesser Noddy [T] 79500                     79500 79500
Black Noddy [T]   50-100     11.9-13.1e4             119340 130840

Table 1. Estimates of numbers of breeding pairs of Australian seabirds along sections of the Australian coast and Coral Sea: 1, Cape Leewin to Shark Bay; 2, Shark Bay to Northern Territory border; 3, Northern Territory & Gulf of Carpentaria; 4, Coral Sea; 5, Cape York to New South Wales border; 6, New South Wales; 7, Victoria; 8, South Australia; 9, South Australian border to Cape Leeuwin; 10, Bass Strait; 11, southern Tasmania. [C], [T] and [I] refer to Southern Ocean species, tropical species and those derived from tropical species, respectively; e3, e4 and e6 = x 1000, 10 000 and 1 000 000; br = breeding, but numbers not estimated.

The Seabird Islands Report (SIR) series (Numbers 1-215 published in The Australian Bird Bander Volumes 11-14, 1973-1977 and its successor, Corella Volumes 1-16, 1977-1992) formed a primary data source. Though incomplete, this series provided useful regional comparisons in this report. Other data sources are Serventy (1952), Green and Mollison (1961), Serventy and Whittell (1962), Warham (1962), Stirling, Stirling and Shaughnessy (1970), Lavery and Grimes (1971), Bush and Lodge (1977), Kolichis (1977), Burbidge and George (1978), Cox (1978), Abbott (1979), Storr (1980), Harris and Norman (1981), Whinray (1982), Storr (1984), Berry (1986), Storr, Johnstone and Griffin (1986), Burbidge et al. (1987), Australian National Parks and Wildlife Service (1989) Burbidge and Fuller (1989), Hill and Rosier (1989), Marchant and Higgins (1990), King, Hicks and Cornelius (1992), Walker (1992), King (1993) and Menkhorst (1993).

Population estimates for Western Australian islands are based wholly on unpublished data from the Department of Conservation and Land Management database, developed and maintained by A.A. Burbidge and P.J. Fuller. Similarly, the unpublished seabird island database established by the Tasmanian Department of Parks, Wildlife and Heritage is used here. Estimates for South Australia are based largely on unpublished data held by the Department of Environment and Land Management (Robinson, Canty, Mooney & Rudduck, unpublished manuscript). The SIR series provides limited spatial and temporal coverage for these areas, as well as for Torres Strait, the Coral Sea and parts of the Great Barrier Reef.

To improve their robustness, estimates have been expressed as maximum and minimum values where possible. Estimates derived from non-numerical comments by several observers were expressed as maximum and minimum numbers of breeding pairs in the following manner: 'few pairs' or 'several tens of thousands' became 3-7 pairs or 30 000-70 000, on the basis that 3 x 10n and 7 x 10n are appropriate maximum and minimum levels around a central midpoint of 5 x 10n. Where estimates were available within the same year or 2-3 year period, they were expressed as maximum and minimum numbers.

Several factors increase the likelihood of error in these estimates.

Population estimates based on nesting burrow densities are almost certainly too high, because burrow occupancy by breeders may range from 43% to 86% in sooty, short-tailed or wedge-tailed shearwaters and little penguins (Harris & Norman 1981, Marchant & Higgins 1990, Dyer & Hill 1992). Estimates for South Australia and Western Australia were based on burrow occupancy rates. It is possible also that colonies of some surface-nesting species which breed almost continuously (such as some tropical terns and boobies) may comprise sub-populations with different breeding seasons. This factor, coupled with interannual fluctuations in the size and timing of breeding, suggest that the single counts made for many of the island seabird populations are probably too low ( Serventy & Warham 1971, King, Hicks & Cornelius 1992).

Conversely, addition of records for different years from several islands in the same region will overestimate numbers for species which frequently change breeding sites (for example, pied cormorants, and crested, roseate or fairy terns). Less information is available for remote islands or those difficult to land on and survey data are often spread over the last two decades. Publication dates of the SIR series indicate that 14% of islands were surveyed before 1975, 59% from 1975-1984 and 26% after 1984.

The total estimated number for each Australian seabird species (Table 1) ranges across seven orders of magnitude. Four species are known from fewer than 100 breeding pairs. Breeding of the white-fronted tern was first proven in 1979 (Whinray 1982). Less certain is the status of the miniscule, incipient colonies of white-tailed tropicbirds, herald petrels and black-winged petrels. The status of Gould's petrel and the little tern, two of five species with fewer than 1000 breeding pairs, are discussed below under 'Threatened species'. Although low in numbers, the widespread, endemic Pacific gull seems secure, and numbers of the burrowing common diving-petrel are more likely to be underestimated than those for most species. The kelp gull is considered a recent arrival in Australian waters (Serventy & Warham 1971).

At the other end of the scale, eleven species exceed an estimated 100 000 pairs (little penguin, fairy prion, three shearwater species, white-faced storm-petrel, common diving-petrel

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