Quick Dips

Feast and Famine for Stitchbirds

The transfer of stitchbirds from Little Barrier to Mokoia Island could show for the first time why so many similar transfers have been unsuccessful in the past, according to project organiser Dr Doug Armstrong from Massey University's Department of Ecology.

He says that the reason for the failure of previous transfers involving stitchbirds could be a natural shortage of carbohydrate food, such as nectar and fruit, for the birds to eat.

To test this theory, the birds are being fed an artificial nectar developed in Australia. When they are happily established on the island, probably early next year, the food will be taken away for a fortnight, then re-introduced on a fortnightly rotation, to see how they adapt to the island's natural food sources.

After the birds have had access to the feeders for two weeks, they will be weighed by electronic scales on the feeding platform. Then the feeders will be removed for a fortnight, and when the food is introduced again, the scales will register whether the birds have lost condition during that time.

Mokoia Island was chosen for the stitchbird transfer because it is now rat-free, and it supports a good population of another nectar-feeding bird, the tui. While the food supply is good, the aggressive tuis could cause problems for the new arrivals, so it is important to determine what the food supply is like, and what access the stitchbirds have to it.

The project will also measure trends in the tui population over time, to find out whether the tui leave when there is not so much nectar, or whether they will push the stitchbirds off the food supply when food is scarce.

"If we note the stitchbird visiting plants that have less nectar than others, we can conclude that the tuis are probably pushing them out," says Armstrong. "Our research should show what times if any the birds need supplementary food."

If the tests prove that the stitchbirds need supplementary feeding, a permanent feeding station will be maintained, with artificial nectar always available at times of scarcity. A longer-term solution will be to plant species that will flower and/or fruit at those times of the year.

The island is volcanic and steep. Its 135 hectares are densely vegetated and Armstrong says it could be an important place for future translocations -- what could work for the stitchbird could work for other endangered birds as well. Introductions of robins in 1991 and saddlebacks in 1992 have resulted in rapidly expanding populations.

Paul Jansen of DOC, Rotorua, has played a major role in the project, involving pupils from the local Rotorua Lakes High School in transferring the stitchbirds from Little Barrier to Mokoia Island. The pupils have also built 60 nest boxes and erected 40 of these in gullies on the north side of the island. More have subsequently been erected by Armstrong.

Several birds have already started nesting in the boxes supplied by the school pupils.

"This means they are happy with their environment, and obviously getting plenty to eat," says Armstrong.