A new source of disturbance for Eastern Curlews

Tuesday, 18 July 2023

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A new source of disturbance for Eastern Curlews

The increasing use of drones is becoming a conservation issue

As if Eastern Curlews need another threat. The once-healthy population of these critically endangered birds has collapsed in recent decades, due mainly to the loss of their coastal habitat right along the East Asian–Australasian Flyway (including in Australia), as well as disturbance in their feeding and roosting areas. This disturbance has previously largely been in the form of people and their boats and dogs. However, a new study by the University of Queensland has revealed a new source of disturbance from an increasingly popular pastime — flying drones.

The study, conducted in Moreton Bay in south-eastern Queensland, saw drones approach flocks of shorebirds on 240 occasions, recording the level of disturbance caused by approaching them at different heights.

“Eleven species were generally unaffected by the drones,” said Joshua Wilson, from UQ’s School of the Environment, “with less than 20 per cent probability that they would take flight when approached by a drone flying higher than 60 metres.”

“The stark exception was the Critically Endangered Eastern Curlew, which reacted by becoming startled and flying away even when we flew above them at the legal ceiling of 120 metres,” he said.

“This then had a domino effect on nearby species, which would also become startled [by the fleeing curlews] and fly away in response to the eastern curlew’s reaction.”

The study’s findings back up previous studies which have found that, among shorebirds, the Eastern Curlew is the species that is most sensitive to disturbance, and the most readily flushed into flight by nearby human activities, which may disturb the birds from more than 100 metres away.

Disturbance of these shorebirds uses up vital energy, often at a time when the birds are urgently foraging to increase their energy reserves to sustain their long-haul flight to their breeding grounds in the Northern Hemisphere. Further, the birds may avoid areas that experience repeated disturbance, even though these sites may provide a bounteous source of food.

“Drone use [especially in coastal areas] is increasing dramatically, leading to concerns they are yet another source of disturbance for birds that are already critically endangered,” Mr Wilson said.

It seems clear that the use of drones near flocks of birds needs to be regulated, especially in areas supporting species, such as the Eastern Curlew, that are considered to be at-risk and highly sensitive to disturbance.