Robins thrive after 1080 drop, study finds

A small population of robins in the Silver Peaks survived a 1080 drop and even flourished due to the poison killing its predators, a University of Otago study has found.

The Animal Health Board, which undertook the drop and helped fund the study, said it challenged some of the claims about the negative impacts of 1080 on wildlife.

The South Island robin is a protected native species and the population in Dunedin is only one of two remaining on the east coast. The other is a small population in Kaikoura.

Robins are a good indicator on the effect of 1080 as they are ground feeders and susceptible to pecking at bait.

Conducted by the university's threatened birds research group, the study monitored 19 banded robins in the Silver Peaks before and after 1080 was dropped.

Another population in the Silver Stream, where no 1080 was dropped, was also monitored.

Research supervisor Associate Prof Ian Jamieson said it was a rare opportunity to study the effects of 1080 on an intensively studied population of native birds.

In previous 1080 drops, before the quality of baits was improved and poison levels were reduced, it had been thought 20% to 30% of robins could have been killed directly or indirectly, he said.

"We also wanted to see whether or not the current practice of pre-feeding with non-toxic pellets to overcome potential bait shyness in possums had any negative impact on birds."

Researchers also monitored possum and rat numbers, the robins' major nest predators, at the two sites to see how effective 1080 was at killing them.

No sign of rats or possums was found 11 days after the operation and again 80 days later. By comparison, there was no change in numbers in the Silver Stream.

Nests in the Silver Peaks that were monitored produced at least one fledgling, while at the Silver Stream only 8% of nests produced at least one fledgling.

The results of the study showed that pre-feeding bait had no negative effect on the birds, he said.

"Secondly, it knocked the possum and rat numbers down to almost zero; and thirdly, that robins experienced relatively high breeding success when predator numbers were low."

The population would continue to be monitored to see how long rat numbers remained low and the study would need to be repeated. The aim was to model how often 1080 had to be used to allow the population to recover, he said.

AHB research and Tb eradication manager Paul Livingstone said the board hoped the study would help reassure people aerial 1080 pest-control operations had "genuinely changed for the better".

rebecca.fox@odt.co.nz