A Bird in the Hand…
San Diego Zoo Global researchers recently completed three years of intensive research on the North Island brown kiwi Apteryx mantelli in New Zealand. San Diego Zoo Institute for Conservation Research post-doctoral fellow, Dr. Sarah Jamieson, moved from her home in Canada to the north island of New Zealand to study these elusive nocturnal creatures in their native habitat. Most of her time was spent on a remote island where brown kiwi live in relative abundance.
In collaboration with the Ecology Group of the Institute of Natural Resources at Massey University, Dr. Jamieson radio-tracked nearly 50 free-ranging kiwi in order to document the roosting habits and hatching success in this endemic species. She found that 90% of kiwi roost in forest habitat and spent most of their time inside burrows, with a preference for living trees and, to lesser extent, dead trees and holes in the ground. Her data suggest that a mosaic of habitat, including a large dynamic forest, is needed to meet the roosting requirements of a healthy kiwi population in the wild.
This finding strongly supports the preservation of forest ecosystems in New Zealand as an integral part of kiwi conservation.
It is well known that kiwi exhibit a rather unusual incubation scheme with the male sitting on the eggs until hatching while the female pays little to no attention to her offspring. Dr. Jamieson recorded as many as three males incubating a single egg and, in a most interesting discovery, found that the more males incubating a nest, the lower the probability the eggs will hatch. This finding argues against the current theory that more males should result in more consistent incubation.
She hypothesizes that multiple males might lead to poor hatching success because eggs are neglected or suffer physical damage as males vie for superior position to incubate the clutch. She also observed males occasionally waiting to initiate incubation until a second egg is laid (20 – 25 days later), much to the detriment of the first egg.
These two problems can be overcome with human intervention, and an important component of kiwi conservation in New Zealand involves removing eggs from wild birds to hatch in captivity and releasing the young at new sites. Dr. Jamieson’s findings will be helpful to managers in deciding which eggs to extract, concentrating on nests with multiple males or with males that fail to incubate first eggs within the first few days.
Through her work, it is now confirmed that this intervention will not significantly reduce kiwi chick production in the wild, as she documented re-nesting as well as double brooding.
Kiwi pairs may re-nest to replace a failed nest in which eggs did not hatch, and can also lay a second nest after successfully hatching the first nest. Like in the successful California condor recovery program, kiwi eggs can be removed from a nest for artificial incubation and hatching while the parents start again with a second brood. Artificial rearing of kiwi chicks has another advantage. Releasing these young birds when they have attained a sufficient size significantly reduces the threat of predation by feral cats that routinely take younger, smaller chicks.
Over the next year Dr. Jamieson will be analyzing the data she collected over the last three years and preparing a number of manuscripts for publication.
Keep an eye out for announcements of her articles in future Wildlife Conservancy communications.
Barbara Durrant, Ph.D., Director Reproductive Physiology Division, San Diego Zoo Global