A naturalist has warned against the use of rat poisons that could kill off the barn owls that prey on them.

David Wingate said that anticoagulant poisons that caused internal bleeding in rats had also killed owls that ate them.

He added that the use of stronger poisons on rats was “systematically killing off our very best ally in the rat control business”.

Dr Wingate said: “The barn owl is in trouble in Bermuda – and the cause is the very thing that we and our pest control officers are using to control the rats that they eat.”

He was writing in the latest newsletter from the Audubon Society, a bird conservation organisation.

Dr Wingate said that anticoagulant poisons, designed to stop blood from clotting, made the rats weaker every time they ate it until they eventually died.

But he added that rats had become resistant to some poisons and that stronger anticoagulants were being used.

Dr Wingate said that the newer poisons were strong enough to kill an owl after they ate just one poisoned rat.

He added that owls used to be safe against the poisons because they did not eat enough poisoned rats to affect them.

But he warned stronger rat-killers meant larger doses of poison.

Dr Wingate said that Bruce Lorhan, an owl conservationist, planned to meet the Government’s Vector Control Department to discuss another pest control programme that could reduce the rat population without killing owls

He added: “There are lots of things we can do, including wider use of an ingenious trap developed in New Zealand which can kill multiple rats in succession and the erection of barn owl nesting boxes.”

Barn owls, Tyto alba, were first spotted on Nonsuch Island in 1931 by American naturalist William Beebe – about 300 years after the black rat arrived in Bermuda in the early 1600s.

They are the most widespread species of landbirds in the world and can be found on every continent, except Antarctica.

The Audubon Society is planning a research project on barn owls to be carried out in 2022 and would appreciate any are hoping to gather as many Barn Owl sightings as possible, particularly any known roosts or nests. Readers who make such sightings, should send them - with photographs if possible - to info@audubon.bm