The Tiwi Islands, consisting of Melville and Bathurst Islands, are the largest landmass off the Australian coast after Tasmania. They have been isolated from the mainland since the last ice age and are largely covered with eucalypt forest on a gently sloping lateritic plateau. Small rainforest patches occur in association with perennial freshwater springs, and mangroves surround numerous inlets. The climate is monsoonal, the wet season from November to April having the highest rainfall in the Northern Territory, with an average of at least 1400 mm per year. Two threatened species, the Red Goshawk and the Partridge Pigeon, are exceptionally common on the islands compared to the rest of their range. Red Goshawks are most often found in extensive open forest, open woodlands and riparian vegetation dominated by mature Eucalyptus tetrodonta, Woollybutt Eucalyptus miniata, and Cadjeputs Melaleuca leucadendron (Aumann and Baker-Gabb 1991, Woinarski et al. 2000). Several endemic subspecies are also threatened, including those of the Masked Owl and the Hooded Robin. Plantation forestry operations of Acacia mangium may eventually cover 10% of the islands but it is currently intended that the remainder of the islands remain uncleared. Populations of threatened birds are being monitored as part of the forestry operations and there is active management of other threatening processes.
There is a high level of endemism at the subspecific level on the Tiwi Islands. Of these, the Masked Owl Tyto novaehollandiae melvillensis is considered Endangered and the Hooded Robin Melanodryas cucullata melvillensis is Endangered and may be Extinct, as there have been no records for ten years despite searching. The islands are a stronghold for Red Goshawk, with the Recovery Plan noting that ten pairs nested on average 8 km apart on Melville Island (D Baker-Gabb unpublished data), suggesting a territory size of c.50 km². This contrasts with one measured home range size of c.200 km² on the mainland (Aumann and Baker-Gabb 1991) and led Woinarski et al. (2000) to suggest there were 40-80 pairs on the islands. Chatto (2003) estimated 40,000 mixed waders in October 1993, which is likely to include at least 1% of the flway populations of Great Knot, Red-necked Stint, Greater Sand Plover and Bar-tailed Godwit.
Non-bird biodiversity: Tiwi Islands IBA supports a range of endemic flora, particularly associated with rainforest patches, including 64 species that are either threatened or data deficient and 11 species that are endemic to the Tiwi Islands. It also supports a number of other threatened animals including Brush-tailed Tree-rat Conilurus penicillatus, Northern Brush-tailed Phascogale Phascogale pirata, False Water-rat Xeromys myoides and the Endangered Butlers Dunnart Sminthopsis butleri. Several species of threatened sea turtle nest on the beaches (Woinarski et al. 2004a,b,c).
Pressure/threats to key biodiversity
Adaptively manage forestry operations to ensure viable populations of key species are maintained on the Tiwi Islands. Implement appropriate fire regimes for key species such as Partridge Pigeon.
Conservation responses/actions for key biodiversity
The Tiwi Islands are classified as a site of conservation significance by the Northern Territory Government (Harrison et al. 2009; Ward & Harrison 2009). Surveys have been undertaken during the last five years. Monitoring of Red Goshawks and Partridge Pigeons is being undertaken in association with forestry operations. Currently, forestry operations are also paying for natural resource rangers to manage threats, including weeds, fire and feral animals.
BirdLife International (2019) Important Bird Areas factsheet: Tiwi Islands. Downloaded from
http://www.birdlife.org on 15/10/2019.