Document ID: chunk:federal_register_of_legislation:F2006L03945:body:0:p5
Version: federal_register_of_legislation:F2006L03945
Segment Type: other
Provision Reference: 
Character Range: 10815–13570

– 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 the eventual demise of the CBBR population. Cushman (1995) and Polis et al. (1997) had established that marine inputs of organic carbon and nutrients, via seabirds' use of small islands for nesting, contributed greatly to such islands' food-web budgets, with benefits (additional food and nutrition) flowing to all parts of the food chain. For detritivores and occasional predators of seabird nests, like CBBRs (Marchant & Higgins 1993), the benefits are obvious, and an association between the rails and seabird colonies has been noted before (Schodde & de Naurois 1982). This hypothesis can be tested with the planned reintroduction of CBBR, in that population densities would not be as great in the absence of breeding seabirds under the assertion. Ideally, habitat restoration though selective clearing of undesirable plants and revegetation would be implemented, with the eventual supplementary aim of restoring breeding habitat on the Southern Atoll for forest-nesting seabirds.

Cats (Felis cattus)  Cats are known to prey upon CBBR. The last individual definitely found on West Island was probably killed by a domestic cat in 1991 (Stokes 1994). Cats are assumed to have been introduced by early settlers (Algar et al. 2002). They were not mentioned as a threat to bird populations by Gibson-Hill in the 1940s (Gibson-Hill 1949), but were noted as such in the 1970s and 1980s (e.g. Stokes et al. 1984). The persistence of CBBR on the Southern Atoll for approximately 150 years in the presence of cats indicates that predation by cats was not the lone factor leading to the demise of the rail. However, any undue pressure on small populations has a large effect. Increases in cat numbers often coincides with increases in human population, especially with an increases in food waste, as may have occurred with changes to land use and administrative arrangements during the 1970s (when a large mainland Australian population was established on West Island).

Cats are thought to have played a significant role in the extirpation of CBBR from West Island. Cats are currently known to occur on three islands on the SA, namely West Island, Home Island and South Island (Algar et al. 2002). The CKI Shire Council has been running a feral cat control program on West and Home Islands since 2000 and these efforts have considerably reduced the number of feral cats, at least for short periods. The threat has not been eliminated and the control program is continuing. Surveys conducted by Algar et al. (2002) found no evidence