‘Many observers believe it produces the most beautiful song of any New Zealand bird’

Great Stories of New Zealand Conservation tells 50 thought-provoking and inspiring stories of conservation and ecological projects across the motu. In this extract, author Alan Froggatt details the translocation of the North Island Kōkako.

This handsome wattle bird with beautifully soft silky feathers, rakish mask and a long-curved tail can live for 18-24 years and is about the size of an Australasian magpie. Because of its short, round wings, it can only fly short distances, but it can glide great distances between trees and down gullies. It is seldom seen out of cover but can sometimes be heard crashing around high in the canopy. Like its crow ancestors, it can be inquisitive, shy, and crafty, and is very intelligent.

The only discernible difference between this species and the extinct South Island bird is that the South Island bird had yellow or orange wattles rather than the blue of the North Island bird. Molecular studies support the theory that it arrived in New Zealand from Australia between 34 and 39 million years ago. In doing so it may have island hopped across the Tasman Sea using the now submerged islands of the Lord Howe Rise and Norfolk Ridge as well as the prevailing westerly wind.

It usually only calls at dawn, when the bell-like song of a breeding pair can last up to an hour. This is said to be the longest song of any songbird in the world. Its loud and varied call ranges from a loud cackle and full organ song with beautiful notes to a tūī-like soft talking. Some have described this call as a stunning piece of music – slow, haunting, bell-like and, clear. Many observers believe it produces the most beautiful song of any New Zealand bird.

Kōkako from different regions in the North Island sing differently. Birds living in the same territory will share the same local dialect but there can be differences in dialects between populations. Most pairs will attempt to breed in all seasons but will only mate with another who understands its song dialect. This presents problems, as birds selected for translocation to any particular site should be from the same territory population.

Both species of kōkako were decimated by ship rats and stoats and food reduction caused by possums. The availability of good food supply remains important in achieving a successful breeding season. In 1999, there were 330 breeding pairs. Following the introduction and more intensive use of poisons and an array of sophisticated traps numbers began to increase. As mentioned before, new populations are established by translocation from two different territory populations. Serious efforts began in 1895-1907 with numbers increasing dramatically from 1964.

The deliberate movement and release of wildlife remains of crucial importance in the management of New Zealand’s threatened birds, and as a part of key site restoration projects.

Translocation of all avian species can be financially, logistically, and scientifically challenging and could fail for many reasons among which are stress on the birds during transfer, food sources becoming short, disease, and the unexpected arrival of predators. To add to the problem, several species such as weka, kea and shore plover have a propensity to return to their home range. Despite these issues notable successes have been achieved.

It is not just the number of birds in a species population that indicates whether or not it is at risk of becoming extinct. It is also about the genetic diversity within that population. A tiny population with a high genetic diversity may have better long-term prospects of recovery than a larger, more homogeneous one.

When there is slight variation between individuals, there is less resilience in that population to events such as a new disease, parasite infestation or the impacts of global warming. Thus, determining and maintaining genetic diversity within the country’s many endangered species, and maintaining a pure genetic line in special cases, has become of increasing concern to conservationists.

Translocations have been a crucially important part of bird conservation management in New Zealand for over a century. Improving success rates have been due to advances in techniques, (especially the use of newly developed mist-nets), developments in island pest eradications, increasingly effective conservation agencies, and the use of predator-resistant fencing to allow the reintroduction of the most vulnerable species back to the mainland.

Since 1981, there have been a total of 37 successful translocations of the North Island kōkako to Puketi Forest, Trounson Kauri Park, the Hunua Ranges Regional Park, Rangitoto Range, Pureora Forest Park and the Otamatuna forest of Te Urewera, and to 6 reserves in the North Island and 4 off-shore wildlife sanctuaries of which Kāpiti Island is the most important in maintaining a viable population against extinction. Little Barrier Island though remains a stronghold with reportedly some 100 pairs allegedly ‘bounding about like squirrels.’

By 2008, there were 770 pairs in the country. Then in 2018 after 1080 operations in the Hunua Ranges in the Auckland region the numbers were reported as soaring. They can now also be found in the Kaimai-Mamuku Forest Park and have become established in Auckland’s Waitakere Ranges. But its continued survival is dependent on maintaining sustained control of key pests and good genetic health.

In 2018, Te Aroaro o Kahu Restoration Society took out the New Zealand Biosecurity Department of Conservation Community Award for restoring kōkako to the Pirongia State Forest Park not far from Hamilton city. This society has been so successful the birds are no longer considered endangered there.

In 2021, another 11 birds were translocated to Kāpiti Island from Pureora forest in the Waikato with another 35 to follow by 2023 to inject genetic diversity into the local population of 92 breeding pairs. This was made possible through a new partnership between DOC and Fonterra Brands New Zealand supported by the local iwi Ngāti Toa, Te Ati Awa ki Whakarongotai and Ngāti Raukawa.

While kōkako had been breeding well on the island and numbers had nearly doubled over the past three to five years the founding population was not as robust as it could be. This top-up of new bloodlines should result in a much more secure population. That is after the new birds learn to call in the local dialect of resident kōkako. By this time 11,000 other translocations involving 55 species of other birds had resulted in the establishment of 41 new populations of these other species. A further 7 such translocations were in progress during the writing of this book.

In 1990, there were 610 kōkako living in the wild. At the time of writing there were more than 3,000 living in the wild. But it seems the Australasian harrier hawk and the endemic breeding long tailed cuckoo may have begun taking kōkako chicks. This is of concern and research is underway to verify the evidence before a course of action can be considered.

Extracted from Great Stories of New Zealand Conservation by Alan Froggatt. RRP: $39.99 (White Cloud Books). Out now.