Alligator Rivers Floodplains

Site description (2008 baseline):

Site location and context
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).

Key biodiversity
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.

Non-bird 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.

Pressure/threats to key biodiversity
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.

Conservation responses/actions for key biodiversity
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).

Protected areas
IBA overlaps Kakadu and Mary River National Parks.

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

Site access / Land-owner requests
Much of this IBA is on private or Traditionally Owned land.

Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Alligator Rivers Floodplains. Downloaded from on 22/02/2024.