How Operation Nest Egg works:
1Monitoring Breeding Pairs
2Collecting eggs or chicks
5Release back into the wild
Monitoring breeding pairs
Credit: Rod Morris
The first step in Operation Nest Egg is the biggest-finding and monitoring breeding pairs of kiwi takes up 50% of the overall effort and resources.
Pairs need to be located and transmitters attached to one or both parents to determine if they are nesting. With brown kiwi, only males are monitored as they do all the incubating-when their behaviour changes it indicates they are sitting on an egg. With other kiwi taxa, males and females share incubation.
Choosing the optimal time to remove an egg is vital. Too soon, and the egg could fail. Not only that, it takes up a lot more human resources to keep it alive, warm and well in a captive rearing facility. Too late, and the egg may have been predated or flooded out, or may have hatched, which means its parents are less likely to lay another clutch that season, which means the population will not grow as quickly. For this reason, the Department of Conservation collects more eggs than chicks.
The aim is to collect eggs that are at least 25 days old. If less than 10 days old, there is just a 1% chance of hatching success. If 10–20 days old, the likelihood of success reaches 20%. If the egg is 30 days old, success is 75%, and by 70 days, the chance of hatching a chick reaches 90%.
Clever technology is helping kiwi workers get the timing just right:
- One, known as the 'Egg timer™', electronically monitors breeding adult birds. When their movement patterns change, it's clear that they have begun incubating the egg and kiwi workers can then calculate the best time to collect it. This saves hours of time that used to be spent keeping track of breeding pairs.
- The Egg timer's™ successor is the 'Chick timer™'. This helps field workers pick up newly hatched wild chicks rather than eggs. This is a good option if there is a risk that an adult bird, when disturbed, could stomp on and break the egg. It is also useful if the burrows are too deep to successfully retrieve the egg - such as with great spotted kiwi and rowi.
Collecting eggs or chicks
Once the eggs or young chicks are collected from nests in the wild, they are transferred to captive rearing facilities.
If an egg is being transported, special containers are used to keep it secure and warm. Newly hatched chicks are also carried in special boxes, but if an older chick is being moved, it goes into a carry box similar to the ones used for adult kiwi.
The aim is to get the precious cargo to a captive rearing facility as soon as possible. Twelve hours away from the nest is maximum time limit for an egg. Chicks can be on the road for a little longer - while it is important to keep them warm, it’s not necessary to feed them as they live off their retained yolk for the first five days to one week.
Practical hands-on courses are held at Kiwi Encounter, Rainbow Springs, sponsored by BNZ Save the Kiwi Trust, to teach people how to collect and care for eggs and chicks. You can find out more about these courses here.
When it arrives at the captive rearing facility, each egg is ‘candled’, a technique that uses bright light to reveal its contents. This shows whether the egg is alive and what stage of development the embryo has reached.
The success rate for hatching kiwi eggs in captivity is 80–90%, and about 65% of chicks survive to adulthood on average.
Whether they arrive as eggs or hatched chicks, the young birds are kept in a predator-free environment until considered too big for stoats to tackle and kill.
Captive rearing works because kiwi chicks hatch fully feathered and able to look after themselves almost straight away. Birds that hatch like this are called ‘precocial’, while chicks that hatch naked and blind, and need a lot of parental care, are called ‘altricial’ chicks.
A kiwi crèche is either an island an area of land with a special fence built around it to keep predators out, while all predators are removed from within the fence-creating a safe haven. When kiwi chicks are about two weeks old they are moved from the pens in the captive facility to a crèche until they reach a weight at which they can better defend themselves against the paws and jaws of predators.
It is important to get the chicks into crèches as soon as possible, away from the risk of disease and away from people-the young birds need to learn how to be a kiwi and fend for themselves, and not get too used to having people around. Using crèches also helps cut down the costs of Operation Nest Egg as they are less expensive to run than captive rearing facilities.
Crèches have been set up in both the North and South Islands, each one dedicated to just one kiwi species and most of them on islands. Many have been funded and set up by community groups. For example, eastern brown kiwi chicks, from the Kaweka Range, are put into the Pan Pac kiwi creche built and managed by ECOED. Other fenced crèches on the New Zealand mainland, run by community groups, include Maungatautari, Rotokare and the Bois Gentil Crèche, near Greymouth, which holds great spotted kiwi.
Crèches run by the Department of Conservation are mostly all on islands. For example, rowi chicks are transferred to Motuara, in the Marlborough Sounds; Northland brown kiwi are on Motuora; and Haast tokoeka chicks live on Centre and Bute Islands, in Lake Te Anau.
Release back into the wild
When the young crèche birds reach about 1200 grams in weight they are better able to defend themselves against stoats. This is when they can be safely returned to their wild home, or transferred to a new site to establish a new populaton. Local iwi often farewell and/or greet the young kiwi with a welcoming ceremony.
If the birds are going to an established site, they are simply released. If they are part of a new population, then transmitters are attached so the birds’ welfare can be monitored.
If the chick stayed on-site at the hatching and rearing facility, such as Kiwi Encounter in Rainbow Springs, it has to go through a disease-screening quarantine period to make sure it is fit and well and will cope with living in the wild. These young birds will sometimes have a transmitter attached to their leg so that their movement can be monitored once released.
In 1800, millions of kiwi lived in forests, scrub and sand dunes. Today, only about 70,000 kiwi are left in all of New Zealand, and the place we’re most likely to see them is a zoo or bird sanctuary.