NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The Gang-gang Cockatoo ranges in length from 32 to 37 cm, with a wingspan of 62 to 76 cm (Higgins 1999). The species is readily distinguished from other cockatoos of similar size: males are slate grey with a scarlet head and a wispy scarlet crest; females have a grey head and crest, and the feathers on the underparts are edged with salmon pink (Simpson and Day 1996).
2. The Gang-gang Cockatoo is distributed from southern Victoria through south- and central-eastern New South Wales (NSW) (Shields and Crome 1992). The species formerly occurred on King Island, Tasmania, but is now locally extinct. A small introduced population occurs on the western tip of Kangaroo Island, South Australia (Higgins 1999). In NSW, the Gang-gang Cockatoo is distributed from the south-east coast to the Hunter region, and inland to the Central Tablelands and south-west slopes. It occurs regularly in the Australian Capital Territory. Isolated records are known from as far north as Coffs Harbour and as far west as Mudgee (Chambers 1995).
3. In summer, the Gang-gang Cockatoo occupies tall montane forests and woodlands, particularly in heavily timbered and mature wet sclerophyll forests (Frith 1969). The species may also occur in sub-alpine Snow Gum Eucalyptus pauciflora woodland and occasionally in temperate rainforests (Forshaw 1989). In winter, the Gang-gang Cockatoo occurs at lower altitudes in drier, more open eucalypt forests and woodlands, particularly in box-ironbark assemblages, or in dry forest in coastal areas (Shields and Crome 1992). At this time the species may be observed in urban areas including parks and gardens (Morcombe 1986). The species in general, and creches of young birds in particular, undertake nomadic as well as seasonal movements and may occur at apparently random points within the range described above.
4. The Gang-gang Cockatoo requires hollows in the trunks or large limbs of large trees in which to breed (Gibbons 1999, Gibbons and Lindenmayer 2000). Breeding usually occurs in tall mature sclerophyll forests that have a dense understorey, and occasionally in coastal forests. Nests are most commonly recorded in eucalypt hollows in live trees close to water (Beruldsen 1980). Breeding usually occurs between October and January, and individuals are likely to breed from around four years of age (Chambers 1995).
5. Data from the Atlas of Australian Birds clearly indicate that the Gang-gang Cockatoo has declined dramatically within NSW. A comparison of the first and second Atlas of Australian Birds (Barrett and Silcocks 2002) showed that between atlas periods (1977-1981 and 1998-2001), the overall reporting rate for Gang-gang Cockatoos declined by 44% across its NSW range. Within individual bioregions, a decline in reporting rate was reported in the Australian Alps (49%), NSW South Western Slopes (67%), Sydney Basin (57%), South East Corner (44%) and South Eastern Highlands (22%) bioregions. Increases in reporting rates were reported in only two bioregions: the NSW North Coast (69%) and Nandewar (420%) bioregions. Reporting rate is considered an accurate index of distribution for such a readily identifiable bird as the Gang-gang Cockatoo.
6. The causes of these apparent reductions in the distribution and abundance of the Gang-gang Cockatoo are not precisely known. The late age at which it first breeds and the species' dependence and specificity in its preferences for tree hollows may have rendered it vulnerable to decline as a result of habitat loss and degradation. Clearing of native vegetation, which is listed as a Key Threatening Process in Schedule 3 of the Threatened Species Conservation Act, and degradation of habitat e.g. as a result of altered fire regimes, reduces the availability of tree hollows and may reduce the abundance of optimum foraging and roosting habitat. The distribution of the species coincides with cool temperate (Bassian) vegetation (Emison 1982), and climate change may alter the extent and nature of this vegetation. Anthropogenic Climate Change has been listed as a Key Threatening Process in Schedule 3 of the NSW Threatened Species Conservation Act.
7. The Gang-gang Cockatoo is susceptible to Psittacine cirovirus disease (PCD) (McDonald 2004). This disease is known to have increased near Bowral in the southern highlands of New South Wales over the past decade (McDonald 2004). It is spread through contaminated nest chambers and constitutes a further threat to the species.
8. In view of the above the Scientific Committee is of the opinion that the Gang-gang Cockatoo Callocephalon fimbriatum (Grant 1803) is likely to become endangered in nature in New South Wales unless the circumstances and factors threatening its survival or evolutionary development cease to operate.
Dr Lesley Hughes
Proposed Gazettal date: 22/07/05
Exhibition period: 22/07/05 - 16/09/05
Barrett G, Silcocks A (2002) 'Comparison of the first and second Atlas of Australian Birds to determine the conservation status of woodland-dependent and other bird species in New South Wales over the last 20 years.' (Birds Australia: Hawthorn East, Victoria)
Beruldsen G (1980) 'Field Guide to Nests and Eggs of Australian Birds'. (Rigby: Adelaide)
Chambers LE (1995) 'The Gang-gang Cockatoo in field and aviary'. (Victorian Ornithological Research Group: Brunswick East, Victoria.).
Emison W (1982) Wildlife. In: 'Atlas of Victoria'. (Ed. JS Duncan) pp. 44-72. (Government Printer: Melbourne)
Forshaw JM (1989) 'Parrots of the World'. (Landsdown Editions: Willoughby, Sydney)
Gibbons P (1999) Habitat-tree retention in wood production forests. PhD thesis. Australian National University, Canberra
Gibbons P, Lindenmayer D (2000) 'Tree Hollows and Wildlife Conservation in Australia'. (CSIRO Publishing: Canberra)
Higgins PJ (1999) (Ed) 'Handbook of Australian, New Zealand and Antarctic Birds. Volume 4: Parrots to Dollarbird.' (Oxford University Press: Melbourne)
McDonald P (1995) Gang-Gangs in the southern highlands of New South Wales. Observation in the wild and notes on foster care. (Privately Published: 56 Woodbine St, Bowral NSW 2576)
Morecombe M (1986) 'The Great Australian Birdfinder.' (Promotional Reprints: Willoughby)
Shields J, Chrome F (1992) 'Parrots and Pigeons of Australia.' (Angus and Robertson: Sydney)
Simpson K, Day N (1996) 'Field guide to the birds of Australia (5th edn).' (Penguin Books Australia: Ringwood, Vic)