Northern giant-petrel - vulnerable species listing

NSW Scientific Committee - final determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Northern Giant-petrel Macronectes halli Mathews 1912 as a VULNERABLE SPECIES in Schedule 2 of the Act. Listing of vulnerable species is provided for by Part 2 of the Act.

The Scientific Committee has found that:

1. The Northern Giant-petrel Macronectes halli, is a large seabird of length 80-95cm and wingspan 150-210cm. The species is sexually dimorphic, with males markedly larger and heavier-billed than females (Marchant and Higgins 1990). A single colour morph exists, comprising white about the bill and face, a dark grey-brown body, and mottling at the borders. The species is listed as Vulnerable under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.

2. The Northern Giant-petrel has a circumpolar pelagic distribution, predominantly in sub-Antarctic to Antarctic waters north of the Antarctic convergence, usually between 40-64°S in open oceans (Environment Australia 2001). Their range extends into subtropical waters (to 28°S) in winter and early spring, and they are a common visitor in NSW waters, predominantly along the south-east coast during winter and autumn (Blakers et al. 1984, H. Battam pers. comm.). The provenance of Northern Giant-petrels occurring in NSW waters is restricted to Macquarie Island (H. Battam pers. comm.). Adults usually remain near the breeding colonies throughout the year (though some do travel widely) while immature birds make long and poorly known circumpolar and trans-oceanic movements (Marchant and Higgins 1990, Patterson and Hunter 2000). Hence most birds recorded in NSW coastal waters are immature birds (Environment Australia 2001, H. Battam pers. comm.).

3. Breeding in Australian territory is limited to Macquarie Island and occurs during spring and summer. Northern Giant-petrels seldom breed in colonies but rather as dispersed pairs, often amidst tussocks in dense vegetation and areas of broken terrain (Marchant and Higgins 1990, Garnett and Crowley 2000, Environment Australia 2001). A single chick is raised and although breeding occurs annually, approximately 30% of the potential breeding population do not nest (Voisin 1988).

4. The Northern Giant-petrel is an opportunistic scavenger and predator, and is considered to be one of the principal scavengers of the Southern Ocean and a significant terrestrial predator at some localities (Patterson et al. in press). There are marked differences in diet between the sexes; females obtain most of their prey live from the sea, while males also scavenge from the carcases of penguins and seals on land (Hunter 1987, Gonzalez-Solis et al. 2002). At sea, both sexes are aggressive opportunists, feeding on fish, cephalopods, birds and crustaceans, including euphausiids or krill (Marchant and Higgins 1990). The species regularly attends fishing vessels, including trawlers (Marchant and Higgins 1990). Breeding birds forage largely inshore, remaining relatively close to their nesting areas (Marchant and Higgins 1990) but major pelagic excursions have also been recorded (Gonzalez-Solis et al. 2002). During the vulnerable early chick phase adult birds utilise land-based carrion resources (e.g. seals) extensively (Patterson et al. in press). Although representing a small proportion of its total foraging area, potential forage in NSW waters during the winter is nonetheless considered significant for the species (Paterson and Hunter 1988, H. Battam pers. comm.). Juvenile birds are commonly encountered in inshore waters feeding on the cuttlefish Sepeia apama, which dies in large numbers following completion of breeding (H. Battam pers. comm.).

5. Although widely distributed, this species is a large carnivore positioned high in the food web and has a relatively small global population (Environment Australia 2001). The total number of mature Northern Giant-petrels comprising the Macquarie Island sub-population is limited, with an estimated population size of 2,600 (Garnett and Crowley 2000). This population numbered approximately 1000 breeding pairs in 1970/71 (Johnstone 1977) and 1974 (Johnstone 1974), 1485 pairs in 1998/99 (Gales et al. in press, cited in Environment Australia 2001) and 1281 pairs in 1996 (Garnett and Crowley 2000). This population is currently regarded as either stable (T. Reid, pers. comm.) or increasing (Garnett and Crowley 2000, Patterson et al. in press) although there is considerable uncertainty around the population estimates and a number of threats are apparent.

6. A significant threat to Northern Giant-petrels is mortality via longline fishing. 'Incidental catch (or bycatch) of seabirds during oceanic longline fishing operations' is a Commonwealth listed Key Threatening Process under the Environment Protection and Biodiversity Conservation Act 1999. Among other pelagic bird species, the listing identifies Northern Giant-petrels to be adversely affected by longline fishing. Longline fishing has been identified as the primary threat currently affecting giant-petrels (Environment Australia 2001).

7. On their breeding islands, Northern Giant-petrels are threatened by predation from black rats and feral cats, and habitat degradation from introduced rabbits (Patterson et al. in press). Breeding success and/or nest-site selection have probably been adversely affected by rats, and an elevated number of Great Skuas Catharacta skua (Environment Australia 2001), although the threat from the latter has been substantially reduced (Garnett and Crowley 2000). These birds are known to be extremely timid and appear to be highly vulnerable to human disturbance (Patterson et al. in press).

8. Within NSW waters, potential threats are the loss of the southern cuttlefish populations, illegal longline fishing, and oil spills (Environment Australia 2001, H. Battam pers. comm.). Ingestion of plastics and hooks and their regurgitation to chicks, entanglement in marine debris and accumulation of chemical contaminants may also pose risks to this species (Environment Australia 2001). Interactions with trawlers (for example, entanglement in nets or in trawl gear, collisions with apparatus, entrapment in trawl winches) has been a significant cause of mortality in the past, however mortality as a result of trawling operations is now a rare event (Environment Australia 2001).

9. In view of the above the Scientific Committee is of the opinion that the Macronectes halli Mathews 1912 is likely to become endangered unless the circumstances and factors threatening its survival or evolutionary development cease to operate.

Associate Professor Paul Adam
Chairperson
Scientific Committee

Proposed Gazettal date: 14/11/03
Exhibition period: 14/11/03 - 16/01/04

References:
Blakers M, Davies SJJF, Reilly PN (1984) 'The atlas of Australian birds.' (Melbourne University Press, Melbourne).

Environment Australia (2001) 'Recovery plan for albatrosses and giant-petrels.' Environment Australia, Canberra.

Gales R, Brothers N, Terauds A, Copson G (in press) Population status, productivity and at-sea records of albatrosses and giant-petrels breeding on Macquarie Island. Marine Ornithology.

Garnett ST, Crowley GM (2000) 'The action plan for Australian birds.' Environment Australia, Canberra.

Gonzalez-Solüs J, Croxall JP, Briggs DR (2002) Activity patterns of giant petrels, Macronectes spp., using different foraging strategies. Marine Biology 140, 197-204.

Hunter S. (1987) Species and sexual isolation mechanisms in sibling species of giant petrels Macronectes. Polar Biology 7, 295-301.

Johnstone GW (1974) Field characters and behaviour at sea of Giant Petrels in relation to their oceanic distribution. Emu. 74, 209-218.

Johnstone GW (1977) Comparative feeding ecology of the giant-petrels Macronectes giganteus (Gmelin) and M. halli (Matthews). In 'Adaptations within Antarctic Ecosystems' (Ed G. A. Llano) pp. 647-668. (Smithsonian Institute, Washington DC)

Marchant S, Higgins PJ (1990) 'Handbook of Australian, New Zealand and Antarctic Birds, Vol.1.' (Oxford University Press, Melbourne)

Patterson DL, Hunter S (2000). Giant petrel Macronectes spp. band recovery analysis from the International Giant Petrel Banding Project, 1988/89. Marine Ornithology 28, 69-74.

Patterson DL, Woehler EJ, Croxall JP, Poncet S, Fraser WR (in press) Breeding distribution and population status of the Northern Giant-Petrel (Macronectes halli) and the Southern Giant-Petrel (M. giganteus). Marine Ornithology.

Voisin J-F (1988) Breeding biology of the Northern Giant-Petrel Macronectes halli and the Southern Giant-Petrel M. giganteus at Ile de la Possession, Iles Crozet, 1966-1980. Cormorant 16, 65-97.

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