Author: Robertson, H. A. ; Saul, E. K.
Year: 2004
Title: Conservation of Kakerori (Pomarea dimidiata) in the Cook Islands in 2003/04
City: Wellington
Institution: Department of Conservation
Keywords: Conservation; Kakerori; Pomarea dimidiata; Cook Islands

Abstract: In 1989, the kakerori (Pomarea dimidiata) was one of the 10 rarest bird species in the world, with a declining population of just 29 birds. During each breeding season since then, rats have been poisoned within the 155 ha of forested hill country they occupy in the Takitumu Conservation Area in South-eastern Rarotonga. As a result, the kakerori population has rebounded, with a minimum of 292 birds found on Rarotonga in August 2003. In 2001/02, the emphasis of management shifted from the recovery of kakerori to a programme aimed at sustaining the population at 250-300 individuals. The major changes were an experimental reduction in rat poisoning effort to a level where recruitment of kakerori balances annual mortality, and a series of transfers to establish an insurance population on the island of Atiu. In 2003/04, all bait stations were filled fortnightly, rather than the previous mix of weekly and fortnightly refills. This reduced labour cost by 30% to 32 person days, and used a total of 39 kg of Talon (active ingredient brodifacoum), which was only 13% of the maximum annual poison use over the same area during the recovery phase of the programme. Breeding success was high (0.91 fledglings/breeding territory), even in the unpoisoned areas, and a record total of 80 fledgings was detected. The fortnightly poisoning regime offers promise as an effective, cheaper and less toxin-intensive method than that used previsously, and so we recommend maintaining this regime in 2004/05, so that the longer -terms effects can be assessed. A third and final batch of 10 young kakerori was transferred to Atiu island in August 2003. This insurance population is becoming well established; the five breeding pairs monitored in 2003/04 each raised two fledlings, and a minimum of 15 birds was found in May-June 2004 in the small part of the island that was searched.