Tags help kiwi recovery

Radio tagging is being used to discover how inbreeding contributes to the fate of a rare species of kiwi in New Zealand.

New Zealand has around 1600 Little Spotted Kiwi, residing on seven offshore islands and also located at Zealandia eco-sanctuary in Wellington.

Helen Taylor, Researcher and PhD student at the Victoria University of Wellington, is studying the rare species to see what effects inbreeding has on the future of its population. She is able to do this by attaching Sirtrack V2L 152A radio tags to the birds to monitor the population.

Chick timer software, supplied by WildTech, sends data back to Taylor about the tagged birds’ activity patterns and incubation status of the eggs. She believes without this software she would have to spend many hours of observation, which can be expensive and time-consuming.

The radio tags are small (31 x 21 x 16 mm) and are able to be attached to the bird’s leg. They are 2-stage transmitters, powered by a 3.6 V 3 P/N cell. They have an internal antenna and are therefore protected from being broken off. Hospital baby arm bands are used to attach them, with black tape wrapped around them to hold them securely.

“The fitting of the tags this way has been successful for over 25 years. The tags also go through a lot of tests for power output at Sirtrack before they are sent to the user,” said Chris Milne from Sirtrack, which supplied the tags.

Taylor added, “We needed a 2-stage transmitter to run the chick timer software, but the tag also needed to weigh around 12-13 g. Little Spotted Kiwi are the smallest of the five species of kiwi and so cannot wear the larger tags that the bigger species can handle.

“We also wanted a tag with an internal antenna rather than a whip-tail as we’d seen the whip-tails break off in previous studies. In the end, Sirtrack ended up modifying an existing tag to meet our specifications.”

Male kiwis are the ones fitted with the radio tags as they have the responsibility of sitting on the egg once it has been laid by the female. The data is significant as it shows the activity of the male from initially sitting on the egg to nesting with the chick around a month after it hatches.

“The tags emit pulses that tell me … whether the bird is nesting, when it has left the nest and for how long and when incubation began, as well as letting me know when the egg finally hatches,” said Taylor.

Hatched chicks are taken away to be measured and weighed, and unhatched eggs are also taken to be studied to find out why they failed.

Overall, Taylor believes there haven’t been many problems with the tags.

“We had a couple of tags fail once they were on birds, but we’ve always been fortunate enough to be able to retrieve them and fit the birds with the working replacements that Sirtrack has supplied.”

She believes tagging on the females may be able to provide a fuller picture of the problem.

“We do see females remaining in the same area as the nest and we see and hear family groups together once the chick is hatched. It is, however, only the male who ever sits in the nest with the egg and who remains in the nest with the chick for around a month after it hatches.

“It would be great to have tags on females to get a fuller picture of their movements during the nesting season, but obviously that would double the cost of the project.”

Taylor’s PhD funding is for three years and the results of the study will feed into the New Zealand Department of Conservation’s Kiwi Recovery Plan.

The recovery plan lays out management actions for all five species of kiwi to ensure they have the best possible chance of success in the future.

Taylor concluded, “I recently came to the end of my first field season and have just finished fitting all the birds with tags for my second field season, which will run from now until Feb/Mar 2013.”