Document ID: chunk:federal_register_of_legislation:F2006L03945:body:0:p4
Version: federal_register_of_legislation:F2006L03945
Segment Type: other
Provision Reference: 
Character Range: 8121–11043

have been seen foraging on the lagoon shore, and this seems to be a preferred feeding habitat (Hopton 2003; Reid & Hill 2005).

Habitat critical to survival
North Keeling Island is the habitat critical to survival of the CBBR. This island is managed as a National Park and is free of the threatening processes that led to the extirpation of this species from the Southern Atoll. Surveys have shown that CBBR uses all habitats on North Keeling Island. It is the geographic isolation of the island, naturalness of the habitats, abundance of breeding  seabirds and lack of introduced predators that allow the CBBR to survive at high densities.

Figure 1: Cocos (Keeling) Islands

Threats

Single, small isolated population  Small isolated populations are threatened by stochastic extinction through genetic or demographic failure and environmental disaster (such as cyclone, tsunami, severe drought). The current population is sufficiently high for the risk of extinction though genetic or demographic stochastic events to be low. The risk posed by environmental catastrophe (either killing the birds directly or depletion of food sources) also appears low, as the population has survived numerous such events, most recently Tropical Cyclone Walter in April 2001. Although a low risk, contingencies against environmental disaster must be considered, as extinction of small island bird populations by intense storms has occurred (Simberloff 1994).

None of the threats below may have singly led to the extirpation of the CBBR from the Southern Atoll. Rather, a combination is suggested. The North Keeling Island population is not currently exposed to any of these threats but most exist on the larger islands of the Southern Atoll.

Habitat Modification  In the early 1800s the vegetation on the Southern Atoll was largely converted from indigenous forest to coconut plantation monoculture. The coconut plantations maintained an open understorey for ease of collecting coconuts until commercial operations ceased in the late 1970s. Since then the understorey has thickened with a large build up of fallen coconuts, young emergent plants and patches of thick cabbage bush creating dense thickets. It is unknown whether the open understorey of the managed plantations created more suitable habitat for the CBBR than current conditions. However, the dense overgrown habitats now may be habitable for rails, as it is commonly used for cover by two introduced 'rail-like' pheasant species, the Green Junglefowl (Gallus varius) and feral individuals of the Red Junglefowl (G. gallus), and by the recently self-established rail, the White-breasted Waterhen (Amaurornis phoenicurus) native to Indonesia – see Reid & Hill (2005).

Reid (2000) suggested that the loss of a large multi-species seabird rookery from the Southern Atoll probably would have resulted in a lower carrying capacity of the Southern Atoll and led, in part, to