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Bird-friendly Possum Bait

Some exciting research by AgResearch could be good news for the birds currently caught up in the battle against possums in New Zealand.

AgResearch scientists Dr Lindsay Matthews and Tim Day have come up with a compound that poisons possums but that will repel birds, something of a breakthrough for possum control in New Zealand.

Matthews says that some non-target native birds die as a result of primary or secondary poisoning during possum control. It's not known what sort of impact these deaths have on bird population levels, but non-target bird deaths are nevertheless unacceptable to the public.

AgResearch's research aimed to identify bird repellents that are low-cost, acceptable to the target pests, and effective for reducing non-target poisoning.

"So we have been looking at what can control possums and be unattractive to birds."

There are existing methods already, but Matthews believes there is considerable potential for improvement. Removing small bait fragments, using green dye and adding cinnamon oil are currently used to reduce the acceptability of bait to birds.

Other potential methods for reducing bait acceptability include the use of different bait types such as gel bait, or bird-repellent compounds.

However, these alternatives currently have limited use because of the situations in which they can be used (eg. gel bait), their mild deterrent effects when used alone (e.g. coloured dye) or their cost (e.g. cinnamamide).

Two compounds tested by Matthews and Day significantly reduced feeding by sparrows and, when combined, their repellency was enhanced. They were acceptable to possums and rats in lethal-sized baits and should cost under $2 a hectare to apply in pest control operations.

Further studies with these repellents will determine the acceptance of these compounds to pests in toxic bait and the efficacy of these compounds for repelling native birds.