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Location Australia, Northern Territory
Central coordinates 131o 30.41' East  12o 29.16' South
IBA criteria A1, A2, A3, A4i
Area 268,681 ha
Altitude 0 - 10m
Year of IBA assessment 2009

BirdLife Australia



Summary The floodplains support huge numbers of waterbirds, including more than 1% of the world populations of Magpie Goose (up to 800,000), Wandering Whistling-Duck, Pied Heron, Little Curlew, Eastern Curlew, Sharp-tailed Sandpiper, Red-necked Avocet. There are also large breeding colonies of over 30,000 mixed waterbirds, a significant population of Bush Stone-curlew and 11 restricted-range or savanna-biome-restricted species.

Site description The IBA includes the whole floodplains of the Adelaide and Mary Rivers. The Adelaide floodplain extends from south of the Arnhem Highway to the river mouth (The Narrows), mangroves at the base of Cape Hotham peninsula (Wilshire Creek area) and includes Chambers Bay. The Mary River Floodplain extends east to Swim Thrings Creek floodplain and Point Stuart, where it abuts the Alligator Rivers IBA. Floodplain wetlands within the site include Lake Finniss, Melacca and Black Jungle Swamps, the artificial Fogg and Harrison Dams, and various billabongs and lagoons. The unusual morphology of the Mary River floodplain contributes to rapid overtopping of levees and inundation of huge seasonal wetlands, even in years of relatively low rainfalls. Chambers Bay is dominated by sand/mudflats with samphire and mangrove or sand-dune coastlines. The IBA includes waterbird colonies references W23, W25, W27 and W46 in Chatto (2000a). The mean annual rainfall at Middle Point Research Station is approximately 1380 mm, mostly falling in December-March.

Key Biodiversity The waterbird colony on the Adelaide River 15km from its mouth is the largest colony in the Top End, with an estimated 30,000 birds including at least 1500 Great Egret, 6000 Intermediate Egret, 4500 Little Egret, 9500 Cattle Egret (Chatto 2000a). A high count of 33,000-41,000 waterbirds was made at Finniss Lake Lagoon during surveys by Kingsford et al. (2008). Eighty-eight waterbird species recorded on the Directory of Important Wetlands in Australia website database. High counts of waders along Chambers Bay include 2300 Black-winged Stilt, 1960 near threatened Black-tailed Godwit, 1525 Terek Sandpiper, 1650 Grey Plover and 1500 Whimbrel (Chatto 2000b, 2003 and in litt. in Bamford et al. 2008). Coastal mudflats and nearby areas apparently support in the order of 10,000 shorebirds at times and thousands of Oriental Pratincole on the floodplain, before the Wet sets in, and up to 2000 Comb-crested Jacana have been counted at Fogg Dam (August 1983) (DEWHA 2008). Twice, single flocks of more than 2000 Black-tailed Godwit have been observed on swamps 20 km inland from the coast (Chatto 2003). Other species rarely recorded in the IBA include the near threatened Australian Bustard, the restricted-range Yellow-rumped Mannikin and the Australian Little Bittern.

Non-bird biodiversity: A major breeding area for Saltwater Crocodile Crocodylus porosus.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Magpie Goose Anseranas semipalmata resident  800,000 individuals  medium  A4i  Least Concern 
Wandering Whistling-duck Dendrocygna arcuata resident  188,000 individuals  medium  A4i  Least Concern 
Pied Heron Egretta picata unknown  1990-2000  2,000 individuals  medium  A4i  Least Concern 
Bush Thick-knee Burhinus grallarius resident  1998-2008  uncommon  A1  Least Concern 
Red-necked Avocet Recurvirostra novaehollandiae unknown  3,000 individuals  poor  A4i  Least Concern 
Little Curlew Numenius minutus non-breeding  1990-2000  12,000 individuals  poor  A4i  Least Concern 
Far Eastern Curlew Numenius madagascariensis non-breeding  1990-2000  1,050 individuals  medium  A4i  Vulnerable 
Sharp-tailed Sandpiper Calidris acuminata non-breeding  1990-2000  2,500 individuals  medium  A4i  Least Concern 
Varied Lorikeet Psitteuteles versicolor unknown  1998-2008  uncommon  A3  Least Concern 
Rainbow Pitta Pitta iris resident  1998-2008  frequent  A2, A3  Least Concern 
White-gaped Honeyeater Lichenostomus unicolor resident  1998-2008  common  A3  Least Concern 
Yellow-tinted Honeyeater Lichenostomus flavescens resident  1998-2008  rare  A3  Least Concern 
Silver-crowned Friarbird Philemon argenticeps resident  1998-2008  uncommon  A3  Least Concern 
Bar-breasted Honeyeater Ramsayornis fasciatus resident  1998-2008  uncommon  A3  Least Concern 
Banded Honeyeater Certhionyx pectoralis unknown  1998-2008  rare  A3  Least Concern 
Buff-sided Robin Poecilodryas cerviniventris resident  1998-2008  rare  A3  Least Concern 
Australian Yellow White-eye Zosterops luteus resident  1998-2008  rare  A3  Least Concern 
Masked Finch Poephila personata resident  1998-2008  uncommon  A3  Least Concern 
Long-tailed Finch Poephila acuticauda resident  1998-2008  uncommon  A3  Least Concern 

IBA Monitoring

2008 high not assessed not assessed
unset
Medium - based upon reliable but incomplete / partially representative data

Climate change and severe weather storms and floods likely in long term (beyond 4 years) some of area/population (10-49%) slow but significant deterioration medium
Invasive and other problematic species and genes invasive non-native/alien species/diseases - named species happening now some of area/population (10-49%) moderate to rapid deterioration high
Natural system modifications fire & fire suppression - increase in fire frequency/intensity happening now small area/few individuals (<10%) slow but significant deterioration low

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Adelaide River Foreshore Other Conservation Area 254 protected area contained by site 240  
Djukbinj National Park (Aboriginal) 59,027 protected area overlaps with site 30,863  
Fogg Dam Conservation Reserve 1,569 protected area overlaps with site 687  
Harrison Dam Other Conservation Area 3,286 protected area contained by site 3,284  
Lambells Lagoon Other Conservation Area 423 protected area overlaps with site 1,421  
Melacca Swamp Other Conservation Area 2,301 protected area contained by site 2,315  

Habitats

IUCN habitat Habitat detail Extent (% of site)
Forest Melaleuca forests & woodlands  minor
Wetlands (inland) Riverine floodplains  major
Coastline Intertidal mud, sand & salt flats; Mangrove wetlands  minor

Land ownership Woolner, Koolpinyah and Kerlin Stations, Annaburroo, Marrakai, Opium Creek, Melaleuca and Swim Creek pastoral leases. Protected Areas jointly managed by the NT government and the Limilngan-Wulna people. Traditional Ownership.

Land use

Land-use Extent (% of site)
other major
Notes: Traditional Use
nature conservation and research major
rangeland/pastureland minor

Protection status Several national parks and conservation areas.

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

References Bamford, M., Watkins, D., Bancroft, W., Tischler, G. and Wahl, J. (2008) Migratory Shorebirds of the East Asian - Australasian Flyway; Population Estimates and Internationally Important Sites. Canberra, Australia: Wetlands International - Oceania.

Chatto, R. (2000a) 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. (2000b) A management strategy and protected areas system for coastal wildlife. (Documentation of selected sites in the Northern Territory of Australia which would qualify for nomination under the East Asian - Australasian Shorebird Site Network). Unpublished report, 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.

DEWHA (2008) Directory of Important Wetlands in Australia. http://www.environment.gov.au/water/publications/environmental/wetlands/database/ accessed 2008.

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.

Higgins, P.J. and Davies, S.J.J.F. (1996) Handbook of Australian, New Zealand and Antarctic Birds. Volume 3. Melbourne: OUP.

Kingsford, R.T., Halse, S.A. and Porter, J.L. (2008) Aerial surveys of waterbirds - assessing wetland condition. Final report to the National Land & Water Resources Audit. University of New South Wales, Sydney.

Jaensch, R. (1991) Lake Finnis: an internationally significant site for the Little Curlew. Stilt 25: 21.

Smith, F.T.H. (1971) Little Whimbrel in N.T. The Bird Observer 471: 5-6. 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 (2015) Important Bird Areas factsheet: Adelaide and Mary River Floodplains. Downloaded from http://www.birdlife.org on 21/04/2015

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