Stewart Island Sentinel

Phred Dobbins

For conservation purposes, 1080 is generally used as a tool to reduce possum numbers over vast tracts of inaccessible forest. Here we see a more direct use of the toxin as a cat control which has saved the South Island Dotterel.

Phred Dobbins watches his pet cat Benson chasing a fluttering paper on a piece of string.

"You've got to know your enemy if you want to work out ways to defeat them." Wild cats are the mortal enemy of nesting dotterels and defending the birds is Phred's job on Stewart Island. Watching Benson helps him understand how cats think.

The South Island Dotterel is a native shore bird but unlike its North Island relatives who nest on the shore line, these birds prefer to nest in the high alpine scrub above the bush line on Stewart Island. In the past, they were far more widespread but with the introduction to the mainland of predators like cats and stoats, their ground-nesting habits make them easy prey during the nesting season.

Phred received a story from a woman who had known dotterels nesting on her parents' farm in the 1920s at Outram near Dunedin. The birds would have disappeared from there soon after. In the early 1900s cats were common on Stewart Island as they were often kept on ships to reduce rat numbers. Now the descendants of those cats are the curse of ground-nesting dotterels.

"Here on Stewart Island we are lucky that people monitored the dotterels early on." says Phred. "Back in the 1950s there were about 300 birds but even then the population was shrinking."

Phred Dobbins, Stewart Island View

In 1990, the average mortality rate of the monitored dotterels from cats was 23 per cent and in 1992 alarm bells really started ringing as the population crashed to 60 known birds. Something had to be done. Phred was given the role of defending the birds during their vulnerable nesting period from late August until February.

"We set up cat control trials on about 50 per cent of the known population of dotterels using fish-flavoured 1080 baits to kill the wild cats. We needed to find out if the bait was an effective tool before we extended the coverage over all the birds," explains Phred. " I also put in a couple of pellets of cereal rat poison to each bait station to stop rats pinching all the cat bait."

For the first couple of seasons, there was no real difference in the nesting success of the protected birds and the others and Phred began to wonder if his defensive measures were effective. The real crunch came in the third season when there was a massive fruiting of rimu and the rat population exploded. Rats are the favoured food of cats so there was a corresponding increase in cat numbers and the unprotected bird numbers took a dive.

"We knew then that our use of 1080 fish-flavoured bait was effective. We hardly lost any birds in the protected population."

Immediately, the protective regime was adopted for as much of the population as possible and the dotterels have made a steady recovery to the current population of 205 birds.

Jen Hoare tops up a bait station
with fish pellets

The 1080 fish baits are all that stands between existence and oblivion for the South Island Dotterel.

As we wound our way up the South-West Arm of Paterson Inlet in a DoC boat to Rakeahua Landing, Phred explained the level of commitment required to save a species. "It's not easy" he says. "Vigilance is important and I am forever devising new or better strategies to outwit the cats. I watched my pet cat chasing a fluttering paper once and tried putting something similar onto the bait stations to attract the cats but the connection between the movement and the bait was a bit tenuous so there was no real advantage. I'm still thinking about that one. In the meantime I'm going to trap cats as well as use the bait stations this season."

In the cold morning mist we climbed up Mt Rakeahua until we reached the sub alpine scrub. The only noise above the squelching of mud over our boots was the strident calls of kiwi. The mist that clings over the hills can be blasted away by the high winds that are characteristic of this remote part of Stewart Island. One hundred and seventy-six kilometres per hour is the most recent recording.

South Island Dotterel

The dotterels are just beginning to nest and the close cropped alpine vegetation forms a scant cover for the dotterels but is sufficient for a predatory cat to sneak up on an unsuspecting prey.

Phred has set up a series of bait stations that surround the favoured nesting sites for the birds.

"We have 350 bait stations spread over five sites. Some bird populations are scattered over large areas and the effort to protect them is difficult. But, at the end of the day, we are not counting dead cats, we are counting live dotterels and we are making good progress."

Phred talks of rat plagues over the last few years. "I literally stood on three rats when I was going for a walk to Masons Bay," he explains. "That year was really bad for rats and cats were everywhere with such an abundant food supply. We lost 5 per cent of our nesting birds but I would hate to think how bad it might have been if we had not protected them. At least we have smoothed out the bumps in nesting success but there is still no room for complacency."

He smiles at me and says "stopping cat control is not an option and at least it's only for the breeding season."

Phred watches intently as a dotterel tries to distract us from her chosen nest site. All is fine with Phred on guard.

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