Long-term management of kakerori (Pomarea dimidiata) in the Cook Islands Hugh A. Robertson, Ian Karika, George Mateariki, Lynda Nia and Edward K. Saul
DOC Research & Development Series 313
What's it about? The kakerori (Pomarea dimidiata) population had fallen to 29 birds in 1989, before rat poisoning began within 155 ha of forested hill country in the Takitumu Conservation Area (TCA), in southeastern Rarotonga. The population had rebounded to 255 birds by 2001 when management shifted from ‘recovery’ to ‘sustainable management’ of the population at 250–300 individuals. The key elements were to reduce rat poisoning effort so that recruitment of kakerori balanced annual mortality, and to establish an ‘insurance’ population on Atiu, by transferring 30 subadults between 2001 and 2003. In 2001, baiting was reduced from three to one baits per bait station; and from 2003, baits were replenished fortnightly rather than weekly. Labour costs fell 43% to 32 person days per year and Talon® (brodifacoum) rat poison costs fell 25%. Despite the reduced poisoning effort and the transfers, 281 birds were recorded on Rarotonga in 2004. Five tropical cyclones passed through the southern Cook Islands in February–March 2005, causing considerable damage. Although annual mortality was higher than usual, the worst effect became apparent in the following breeding season, when nest predation by rats was unusually high, and the damaged canopy cover left nests exposed to the elements. The population on Rarotonga fell to 254 birds in 2006, so ‘interim’ poisoning was introduced in April and in July 2007 to improve adult survival and further reduce rat numbers. By 2007, the population had increased to 314 birds; 271 on Rarotonga and 43 on Atiu. Profits generated by the TCA’s ecotourism business should be sufficient to sustain the current management of kakerori. Outcome monitoring can reduce to an annual fledgling count, and a two-yearly population census.
The above new publication is now in press and can be downloaded from:
http://www.doc.govt.nz/upload/documents/science-and-technical/drds313entire.pdf (283 KB)
