This work laments the loss through extinction of the South Island Kōkako and the massive decline of the endangered North Island Kōkako in NZ.
The North Island Kōkako, Callaeas cinerea wilsoni has blue wattles (although this colour develops with age: in the young of this bird they are actually coloured a light pink). The North Island Kōkako is endangered, and survives in low numbers in several mainland native forests with the help of government-funded pest control programmes, and captive breeding programmes to help maintain population numbers. New populations are being established through releases on predator-free offshore islands.
The South Island Kōkako, Callaeas cinerea cinerea, by contrast have largely orange wattles, with only a small patch of blue at the base. The South Island Kōkako has fared worse than the North Island Kōkako and was formally declared extinct by the New Zealand Department of Conservation on 16 January 2007.