The islands of this EBA, lying in the mouth of Geelvink bay, are all oceanic in origin and are part of the Indonesian province of Irian Jaya. They include the twin islands of Biak and Supiori (separated from each other by a narrow channel), Numfor and Meos Num, and surrounding smaller islands including Rani and the Pandaidori islands. Nearby Yapen, a larger New Guinean land-bridge island, shares only one restricted-range species with this EBA and is treated as a Secondary Area (s113).

Biak and Supiori have extremely rugged limestone mountains, which in the case of Supiori rise steeply from the sea, while the southern part of Biak is a relatively flat plain. The islands were originally forested, with mangroves in sheltered coastal areas.

This EBA has the most highly endemic avifauna of any of New Guinea's satellite islands (indeed of any single area in the New Guinea region: K. D. Bishop in litt. 1996), including c.19 endemic subspecies.

All the restricted-range species are inhabitants of lowland rain forest, some have been recorded from secondary habitats and a few also occur in mangroves. All species occur on Biak-Supiori apart from Tanysiptera carolinae which is endemic to Numfor.

Three other taxa, Biak Megapode Megapodius freycinet geelvinkianus, Biak Scops-owl Otus magicus beccarii and Biak Golden Monarch Monarcha chrysomela kordensis, are sometimes considered full species, but have not been treated here as such.

Much forest on Biak and Numfor has been destroyed or damaged by logging and subsistence farming. The remainder is under pressure, especially in southern Biak and northern Supiori where there is a growing human population of transmigrants. As the islands are almost entirely raised coralline limestone, the forest does not easily regenerate, and Biak's southern plains are now largely stunted woodland and semi-arid scrub (Bishop 1982, K. D. Bishop in litt. 1996).

Most species confined to this EBA are considered threatened or Near Threatened because of their forest dependency, small range and rarity. Trapping for the bird trade is an additional threat for Eos cyanogenia (and for parrots in general), and hunting is a problem for Victoria Crowned-pigeon Goura victoria, a widespread threatened species (classified as Vulnerable), which also occurs on Biak-Supiori.

Overall this is a very important EBA for avian conservation in New Guinea. Although the forests on Supiori rise steeply, they provide suitable lowland habitat up to c.300 m for many restricted-range species (Bishop 1982), and are therefore a vital refuge. However, the destruction of forest in the northern coastlands may well have untold impacts on nomadic species such as pigeons and parrots, which, although nesting in the hills, may need to forage in the lowlands (K. D. Bishop in litt. 1996).

Two reserves cover lowland and hill forest on Biak-Supiori (Biak Utara Nature Reserve, 110 km², and Pulau Supiori Nature Reserve, 420 km²). A reserve has also been proposed for Numfor (Diamond 1986), which would cover the habitat of its single-island endemic.

A plan to develop Biak as a tourist resort should carefully balance economic development with biodiversity conservation, ecological impact and the traditions of local people (Sujatnika et al. 1995).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Geelvink Islands. Downloaded from https://datazone.birdlife.org/eba/factsheet/174 on 22/11/2024.