Kiwi egg incubation | Research

How can science and research improve outcomes for Aotearoa New Zealand’s most iconic national bird – the kiwi?

This is a question that the Zoo’s curator of birds Dr. Juan Cornejo is seeking to answer, with a new scientific study into the incubation parameters of kiwi eggs.  

In 1995 the Operation Nest Egg (ONE) programme was established, a conservation partnership between the Department of Conservation, Save the Kiwi, kiwi rearing facilities, community conservation groups and mana whenua. In the nearly-three decades since, this programme has proved to be an essential tool for increasing kiwi populations and protecting vulnerable newly hatched chicks from introduced predators like stoats.

Deep in the New Zealand forest, North Island brown kiwi males will sit in a burrow and incubate their eggs for roughly 75-80 days – a huge undertaking and one of the longest incubation periods in birds. In the areas where ONE operates, kiwi eggs are usually collected when the first egg laid (of a two-egg clutch) is at least 40-55  days old and are brought back to specialist organisations like Auckland Zoo for artificial incubation and rearing. Once they reach the right weight, these kiwi chicks are released onto predator free islands until they are large enough to defend themselves from introduced predators, and can be returned back to their original forest homes. Without this conservation intervention, just 5% of kiwi would reach breeding age in the wild - a humbling statistic! Thankfully, through the ONE programme an incredible 65% of kiwi go on to reach adulthood.

Why do conservationists have to wait to lift the eggs? To date, kiwi eggs that are less than 11 days old have had only an 8% chance of hatching success when they are artificially incubated.

The science behind how kiwi eggs are incubated are drawn from two previous studies in 1978 and 2002, but there are still many unknowns when it comes to incubating young eggs.

If bird experts were able to incubate younger eggs - it would help with recovery efforts by providing more options, reducing the risk for the eggs left in the nest and making it more likely that female kiwi would lay more clutches of eggs per season.

Complex problems require ingenuity, and this new study at Auckland Zoo is using the latest technology to better understand kiwi egg incubation.

“A few different variables take place during kiwi egg incubation. This includes the temperature gradient across the egg, the humidity around the egg, and how often and at what angles the egg is turned by the parent,” explains Juan.

To collect the most accurate data, Juan has developed a 3D-printed egg that closely resembles the ‘real thing’ - equipped with Bluetooth dataloggers and the space between them packed by water-filled condoms to replicate how natural eggs conduct heat. The sensors placed under the eggshell will record temperatures and humidity, and allow experts to determine how often and at what angles the egg is turned.

The first pilot egg was placed under a male kiwi at Auckland Zoo to document the incubation parameters. The behaviour of the male kiwi was also recorded using CCTV cameras, and a thermal imaging camera to document the egg’s temperature spatial pattern.

Initial results are encouraging that this technology will be able to teach us more about the incubation process. Additional 3D printed ‘tech eggs’ have been sent to the National Hatchery in Rotorua and Orana Wildlife Park who are collaborating with us to obtain more data for this study. It’s still too soon to draw conclusions but we plan on gathering more data in the upcoming kiwi breeding season of 2023/24.

Juan’s passion for birds started at a very early age and led him into a career in the conservation breeding of birds at some of the best zoological institutions around the world. His interest in research led him to pursue a PhD degree, studying the diet and nutrition of parrot nestlings. Juan joined Auckland Zoo as curator of birds at the end of 2021, and found a great opportunity to further develop his interest in avian incubation by studying the unique kiwi.