Kākerōri conservation history

In the mid-1800s, kākerōri were reported to be common throughout Rarotonga, but following the accidental introduction of ship rats (Rattus rattus) they had become very scarce by the 1880s, and were thought to have become extinct soon after some museum specimens were collected in the early 1900s (Robertson et al. 1994).

In the 1970s, a small population was rediscovered in the rugged lowland hills of the island. David Todd found 21 birds in 1983 and estimated that there were 35–50 birds (David Todd, unpubl. data). In June 1984, Rod Hay and Gerald McCormack caught and colour-banded eight kākerōri near the head of the Tōtoko’itu Valley.

A thorough search of the Tōtoko’itu, Tūroa, Upper Avanā Basin, Lower Avanā Basin, and nearby valleys, revealed a total of 38 birds in 1987 (Robertson et al. 1994). Subsequent annual censuses identified 36 birds in 1988 and then only 29 in 1989,  thusconfirming that the conservation status of kākerōri was ‘critically endangered’ (Collar et al. 1994). At an average rate of population decline of 12% per year, a population viability analysis showed that there was a 50% chance that kākerōri would be functionally extinct (just one bird remaining) by 1998, and a 90% chance by 2002 (Hugh Robertson, unpubl. data).

In 1989, the kākerōri was one of the 10 rarest bird species in the world, and in very urgent need of conservation management (Robertson et al. 1994).

Rat Baiting



Kākerōri Current Population

The 2017 census found 471 kakerori on Rarotonga (Robertson et al 2020). There were 320 birds living in or immediately adjacent to the area of the TCA, which is managed by rat baiting programmes annually. A further 154 were found outside the protected area, mainly in the lower Avana valley (47), Upper Avana Basin (32) or the Taipara Valley (27).

In 2017, the Ātiu population was estimated at about 150 birds (Ed Saul & Lynda Nia pers.comm, in Robertson et al 2020). A survey in 2018 found a minimum of 123 birds, but this was considered to be an underestimate as only 7 yearlings were found, and other bird sightings were difficult to achieve due to inaccessible terrain e.g. makatea (raised coral) habitats (Tui Wright pers.comm, in Robertson et al 2020).

The global population of kakerori in 2017 across these two sites was therefore approximately 600 birds, a more than a 20-fold increase from their lowest recorded population number of 29 in 1989 (Robertson et al 2020).
Population change in the kakerori on Rarotonga, showing the minimum of 29 birds in 1989
Figure 2. Population change in the kakerori on Rarotonga, showing the minimum of 29 birds in 1989 and the peak of 471 birds found in 2017. The drop in numbers between 2003 and 2006 was the result of translocating 30 birds to Ātiu, plus the impacts of 5 cyclones that passed through the southern Cook Islands in February-March 2005 (Robertson et al 2020).