Sites - Important Bird Areas (IBAs)

Summary The extensive floodplains were well surveyed in 1981-1984; extrapolating these maximum estimates to the whole IBA suggest that it supported five million waterbirds, including more than 1% of the world population of 22 species, and significant numbers of three near threatened species, and another 11 restricted-range or savanna-biome-restricted species.

Ornithological information Other high counts of birds (c.60% of IBA counted) included: 3000 White-necked Heron, 15,000 Australian White Ibis, 2,000 Darter, 1,000 Common Sandpiper and 2,300 Gull-billed Tern (Morton et al. 1989). Chatto (2000) listed numbers of nesting waterbirds at seven colonies, totalling at least 13,500 Intermediate Egret (but probably many 1000s more), 6,560 Great Egret, 1,080 Little Egret, 5,550 Cattle Egret (but probably many 1000s more), 7,250 Pied Heron, 1,500 Rufous Night-Heron, 3,800 Little Pied Cormorant and 4,200 Australian White Ibis. Chatto (2003) recorded 7,000 waders in Finke Bay in September 1993. The saline swamps and flats support unknown numbers of Yellow Chats which is otherwise very rare away from inland Australia.

Site description The IBA covers four large adjacent floodplains on the Wildman, Love and Alligator creeks, and the South Alligator, East Alligator, Magela, Cooper and Murgenella rivers. All are primarily seasonally flooded freshwater floodplains, with extensive areas of saltwater floodplains and permanent freshwater swamps. The rivers are tidal in their lower reaches and are associated with extensive tidal flats formed from riverborne mud. Wetland colonies in Chatto (2000) ref: W028, 29, 34, 35, 36, 37, 66. Waterbirds will also use the smaller wetlands inland of these floodplains, which are included in the adjacent Kakadu Savanna IBA. The climate is monsoonal with a hot wet season from November to March accounting for, on average, 90% of the annual rainfall which ranges from approximately 1300-1565 mm (Ramsar information sheet). Kakadu National Park is extremely popular, attracting some 210,000 international and national tourists visit the park each year, a large proportion of whom visit some part or other of the wetlands (Ramsar fact sheet).

Populations of IBA trigger species

Protected areas

Protected area	Designation	Area (ha)	Relationship with IBA	Overlap with IBA (ha)
Kakadu	National Park	1,980,400	protected area overlaps with site	248,294

Habitats

Land ownership Kakadu NP owned by Traditional Owners and managed in partnership with National Parks; wetlands to east owned by Arnhemland ALT.

Land use

Other biodiversity Wetlands species listed in the Ramsar notification include false water rat Xeromys myoides, golden-backed tree rat Mesembriomys macrurus, pig-nosed turtle Carettochelys insculpta, Mariana's hardyhead Craterocephalus marianae, exquisite rainbow fish Melanotaenia exquisita, Midgley's grunter Pingalla midgleyi and the frog Megistolotes lignarius.

Management considerations The National Park has a comprehensive management plan but effective control of invasive alien species, notably Mimosa pigra, requires additional funding. The adjacent floodplains outside the National Park should be managed in the same way, as these are contiguous for both birds and invasive alien species.

Protection status IBA overlaps Kakadu and Mary River National Parks.

Conservation response Much of the area is protected and managed as a National Park. The area is also a Ramsar site; and is classified as a site of conservation significance by the Northern Territory Government (Harrison et al. 2009; Ward & Harrison 2009). There has been extensive research, as summarised in Smyth (1995).

Access/Land-Owner requests Much of this IBA is on private or Traditionally Owned land.

References Bamford, M.J. (1990). RAOU survey of migratory waders in Kakadu National Park: Phase III. Report to ANPWS. RAOU Report No. 70.

Chatto, R. (2000) Waterbird breeding colonies in the Top End of the Northern Territory. Technical Report 69, Parks and Wildlife Commission of the Northern Territory, Palmerston.

Chatto, R. (2003) The distribution and status of shorebirds around the coast and coastal wetlands of the Northern Territory. Technical Report 73, Parks and Wildlife Commission of the Northern Territory, Palmerston.

Chatto, R. (2006) The distribution and status of waterbirds around the coast and coastal wetlands of the Northern Territory. Technical Report 76, Parks and Wildlife Commission of the Northern Territory, Palmerston.

A Directory of Important Wetlands in Australia (accessed March 2007) Kakadu National Park - NT017 Kakadu National Park management plans (website accessed March 2007) http://www.environment.gov.au/parks/kakadu/parkjointmang/mangprograms/index.html

Harrison, L., McGuire, L., Ward, S. Fisher, A., Pavey, C., Fegan, M. and Lynch, B. (2009) An inventory of sites of international and national significance for biodiversity values in the Northern Territory. Department of Natural Resources, Environment, the Arts & Sport, Darwin, NT. Morton, S.R., Brennan, K.G. and Armstrong, M.D. (1989) Distribution and abundance of waterbirds on the Alligator Rivers Region, Northern Territory. Report to the Australian National Parks and Wildlife Service. Office of supervising scientist for the Alligator region, Jabiru, NT.

Smyth, D. (1995) Coming out Bright. An audit of research conducted in KNP 1992-1995. Australian Nature Conservation Agency, Jabiru. Ward, S. and Harrison, L. (2009) Recognising sites of conservation significance for biodiversity values in the Northern Territory. Department of Natural Resources, Environment, the Arts & Sport, Darwin, NT.

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Recommended citation  BirdLife International (2013) Important Bird Areas factsheet: Alligator Rivers Floodplains. Downloaded from http://www.birdlife.org on 20/05/2013

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