yellowhead

The yellowhead, a forest-dwelling passerine endemic to the South Island of New Zealand, has declined in both abundance and range since the arrival of European settlers last century. In the last 30 years it has all but disappeared from the northern half of the South Island but remains widespread in the south. One possible explanation is that the yellowhead has declined in abundance throughout its range, disappearing from less suitable habitats in which it was never very abundant. To test this hypothesis a habitat suitability index was constructed and northern and southern forests compared.