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Location Australia, Northern Territory
Central coordinates 130o 20.00' East  11o 7.04' South
IBA criteria A4i
Area 58 ha
Altitude 0 - 10m
Year of IBA assessment 2009

BirdLife Australia

Summary Seagull Island supports the largest colony of Crested Terns in the world.

Site description Seagull Island is a large sand island mostly covered by grass and vines, about 4 km off the north-western coast of Melville Island, north of Darwin. Island ref S009 in Chatto (2001).

Key Biodiversity Small numbers of Silver Gulls (maximum 800 birds) also nest, and possibly Roseate and Bridled Terns. Large numbers of migrant Little and Common Terns use the island for roosting, as do smaller numbers of Brown Boobies and frigatebirds.

Non-bird biodiversity: Important Olive Ridley Turtle nesting site (Chatto 2001).

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Greater Crested Tern Thalasseus bergii breeding  1999-2006  25,000-29,000 nests  medium  A4i  Least Concern 

IBA Monitoring

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

Biological resource use hunting & collecting terrestrial animals - intentional use (species being assessed is the target) happening now some of area/population (10-49%) no or imperceptible deterioration low
Climate change and severe weather storms and floods likely in long term (beyond 4 years) whole area/population (>90%) moderate to rapid deterioration high
Invasive & other problematic species, genes & diseases problematic native species/diseases - named species happening now some of area/population (10-49%) slow but significant deterioration medium


IUCN habitat Habitat detail Extent (% of site)
Coastline Sand cays, islets & bars  100%

Land ownership Tiwi ALT.

Land use

Land-use Extent (% of site)
other 100%
Notes: Traditional Use

Protection status The traditional owners have a basic system of monitoring the harvest of Crested Tern eggs and sometimes close the island to harvesting. Egg harvests of >1,000 eggs per season are extremely rare. Watanabe (1999) concluded that predation by Silver Gulls was a much greater threat to breeding success.

Access/Land-Owner requests This IBA is on Traditionally Owned land.

Acknowledgements Cyril Kalippa gave permission and Jack Long, Caji Dunn, Kate Hadden and the Tiwi Land Council kindly arranged a visit to the island by Guy Dutson. Nomination endorsed by Tiwi LC in 2006.

References Chatto, R. (2001) The distribution and status of colonial breeding seabirds in the NT. Technical Report 70. Parks and Wildlife Commission of the Northern Territory, Palmerston. Dutson, G. (2006) Crested Terns at Seagull Island, Tiwis, NT. Unpublished report.

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.

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.

Watanabe, Y. (1999) The breeding biology of Crested Tern Sterna bergii on Seagull island, Northern Territory, in relation to egg harvest by Aboriginal people. Northern Territory University.

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Seagull Island (Tiwi Islands). Downloaded from on 24/10/2016

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