Research aims to solve mystery cuckoo movements

Source: NZ Department of Conservation

Date:  14 October 2025

Classified as nationally vulnerable, koekoeā are the larger and rarer of two cuckoo species found in New Zealand, with a distinctive long tail and striking speckled plumage.Compared with other native birds, little is known about them.

DOC Principal Science Monitoring Advisor Terry Greene says the conservation status of koekoeā worsened in the most recent assessment in 2021, due to the declining population in the South Island.

Koekoeā breed only in New Zealand. They lay their eggs in the nests of other bird species such as whitehead, which are left to raise the cuckoo chicks. The adult birds then migrate to spend the winter elsewhere in the Pacific. They are thought to return to their place of birth, despite very large seasonal migration movements. The current fieldwork and research aims to understand their movements within New Zealand, whether remaining populations are genetically different, and how the birds are faring.

“To understand why the population is declining we need to learn about where they go, where they return to, how to count them, and the threats they face – all of which will help with their conservation,” Terry says.

“Koekoeā breeding has been affected by forest clearance and the decline of their preferred host bird species – particularly mohua in the South Island.”

Terry says additional risks and threats for the birds include land use changes, cyclones and predation.

The October fieldwork coincides with the birds’ arrival for breeding – and involves counts of birds in the central North Island as well as catching birds and fitting them with GPS and satellite tracking tags so their movements between New Zealand and Pacific islands, and between different breeding sites within New Zealand, can be monitored.

Terry says using satellite tags will be vital to unveiling the birds’ journeys.

Mist nets will be used to catch the birds, which live near the top of the forest canopy and can be difficult to see despite their loud calls. The fieldwork will take about a week and be followed by data analysis later this year.

Bioeconomy Science Institute Conservation Ecology Researcher Neil Fitzgerald is studying the dispersal of forest birds, including koekoeā, and says understanding their movements is crucial for effective conservation.

“With a cryptic and highly specialised species like koekoeā, there is a real risk that conservation work could be much more difficult and expensive, or even come too late, if we don’t understand what these birds need.”

New tracking and genomic tools will give us new insights, and Neil says an exciting part of his koekoeā research is that the public can help.

“Unfortunately, koekoeā are often killed or injured by flying into windows. On the bright side, even these birds can make an important contribution to our work.”

Here’s how to help:

• Anyone finding an injured koekoeā should phone 0800 DOC HOT (0800 362 468) or contact your nearest DOC office or native bird rescue and then contact Neil.
• If you find a freshly dead koekoeā, please put it in a plastic bag, freeze it, and contact Neil via email – FitzgeraldN@landcareresearch.co.nz 

The team undertaking the research will also be monitoring kererū and kākā population trends. The Pureora Forest is a biodiversity hotspot for the North Island, and a popular location for people naturing through activities such as hunting, hiking or enjoying the Pureora Timber Trail.

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