High Quality Content by WIKIPEDIA articles! The Yellowhead or Mohua (Mohoua ochrocephala) is a small insectivorous, passerine bird endemic to the South Island of New Zealand. Recent classification places this species and its close relative, the Whitehead, in the Whistler family Pachycephalidae. The Yellowhead and the Whitehead have sympatric distributions as, conversely, the latter is found only on the North island and several small islands surrounding it. Although abundant in the 1800s, particularly in beech forests from Nelson and the Marlborough Sounds to Southland and Stewart Island/Rakiura, they declined dramatically in the early 1900s due to the introduction of ship rats and mustelids. Today they have vanished from nearly 75% of their former range. In New Zealand, the Mohua has the status of a protected threatened endemic species. Conservation efforts are being made to ensure its survival and Mohua populations have been established on several predator-free offshore islands,such as Breaksea Island in Fiordland and Ulva Island.