Kaki / black stilt

Status: Nationally Critical

Kakī / black stilt on nest
Kakī / black stilt on nest

Once common throughout New Zealand, the black stilt / kakī is now restricted to the braided rivers and wetlands of the Mackenzie Basin, South Island (distribution map) (with a rare exception in the Ashley River estuary, however, it breeds with a poaka, creating a hybrid). Each pair of black stilt / kakī defends a territory, and nest alone on stable banks near the water in braided riverbeds, side streams, and swamps.

Description

Black stilt (Himantopus novaezelandiae)/ kakī (Maori) are a compact bird about 40cm long. They are very distinctive with completely black plumage and long red legs. Endemic (unique) to New Zealand, they are regarded by Māori as a taonga species (living treasure). Kakī first breed when aged two or three years, and are known to mate for life. If they cannot find a kakī mate, they may sometimes breed with the pied stilt, a close relative. Juveniles are black and white, their plumage darkening to black as they reach maturity. This can lead to them being mistaken for pied stilts.

Release of captive-bred juveniles into the Tasman River.
Release of captive-bred juveniles into the Tasman River.

Conservation efforts

An intensive captive breeding programme has been underway for several years. The short videos on this page explain the problems and what’s being done to prevent the world’s most endangered wading bird from becoming extinct. The programme suffered a  setback in 2015 when a snowstorm collapsed one of their aviaries in Twizel. A new aviary was built to replace it, and the programme continues at Twizel and at the Isaac Conservation Trust near Christchurch.

The Ashley-Rakahuri Rivercare group have also been undertaking predator and weed control in the hope of creating suitable habitat for the re-introduction of the birds into the estuary area.

A day in the life of ‘A day in the life of an aviculturalist‘
2015 snowstorm collapses one of the aviaries in Twizel.
2015 snowstorm collapses one of the aviaries in Twizel.
First chicks for 2019: photo from the Kaki Recovery Programme Facebook page (click on image)

The hybridisation issue

How do you save a species from extinction, when it’s already producing multiple hybrids by breeding with another, close but distinctly different species?

“The philosophical issue of what we are trying to conserve by management has always been around, but the issue becomes bigger with the application of genetical techniques. Are we trying to conserve a population? A species? Phenotype? Behaviour? Composite genotype? A lineage? As many of those things as possible? As introgression has already taken place, ‘purity’ of the species may be a lost cause.” – Wallis, 1999

The issue has raised multiple questions in conservation management, not the least of which is can (and should) you breed a ‘pure’ kakī from a hybrid kakī /poaka?

The results of subsequent research have led to some unexpected and interesting discoveries about the role of genomics in captive-bred programmes and overturns some long-held assumptions.  See ‘References’ below.

This August 2019 video of kakī being released into the wild, also shows how difficult it is to distinguish hybrids from juveniles.

From: Shorebirds – An Identification Guide to the Waders of the World

References and research