At‐nest drone monitoring causes minimal behavioural disturbance in breeding Eurasian Curlew

The use of Unmanned Aerial Vehicles (UAVs, hereafter drones) for monitoring ground‐nesting birds is expanding rapidly, yet the potential for disturbance during nest finding and at‐nest monitoring remains poorly quantified. Notably, there is a lack of knowledge on safe flight protocols and disturbance risk in relation to breeding Eurasian Curlew ( Numenius arquata ), a globally Red Listed species that continues to be the focus of a surge of active research and recovery programs, many of which involve practical interventions and monitoring around the nest.

We assessed behavioural responses of incubating Eurasian Curlew to drone flights across 14 nests in floodplain meadows in lowland England. Each trial started at 50 m above the nest and involved the drone slowly descending to 40, 30 and 25 m, at which point the flight was terminated. The behaviour of the incubating bird was monitored throughout each flight.

Across 26 drone trials, incubating birds showed minimal behavioural disturbance: Although most trials involved birds looking at the drone (80% of the 25 trials with a bird on the nest at 50 m), only three trials (12%) resulted in a bird leaving the nest.

Birds were more likely to look up at the drone as it descended, but the probability of displacement was unrelated to flight height (25–50 m), and displacement was not necessarily preceded by looking. However, the data suggest that birds may be more likely to remain on the nest under higher wind gusts, implying that environmental conditions, rather than drone proximity, could influence the displacement response.

Practical implication . These results indicate that, when operated under the appropriate protocols, drones can provide an effective, low‐impact alternative to traditional, more invasive monitoring methods. For a species of such high conservation concern, minimising disturbance is essential; drone‐based approaches offer opportunities to improve monitoring efficiency and enhance data collection for conservation management of breeding Curlew.