Nightjar bird sitting in a tree

Protected bird species observed in their nests using thermal-sensing drones

Image credit: Pixabay

According to researchers from Cardiff University, thermal-sensing cameras mounted on drones could offer a safer and more cost-effective way to locate nests of the elusive European nightjar in forestry work and construction areas.

Presenting their study at the British Ecological Society’s annual meeting in Birmingham on Monday, ecologists from the university recently conducted a pilot study in Bryn, a Natural Resources Wales managed conifer (cone-bearing seed plants such as pines) plantation in South Wales, to test the suitability of drones to detect nest sites of the protected bird species.

Mike Shewring, a PhD student at the university said: “The current methods of searching for nightjar nests on foot are expensive and can pose a health and safety risk for people, particularly when accessing clear fell worksites,”

“Nightjars are camouflaged to look just like a fallen log or dead wood. They nest on the ground and ‘sit tight’ when approached to avoid detection, which makes it nearly impossible to spot them during the day when they are inactive.” he added.

To test the new method, the team used drones to take thermal photographs at nest sites, where observations and radio tracking previously showed European nightjars were breeding between May and August. Observing the nests from a distance to avoid causing any disturbances to the nest, images were taken at various heights (10, 20 and 50m) at dawn, midday and dusk.

From the photographs, the researchers could detect nests due to the high temperature contrast between the nightjar’s body (40°C) and the colder background area. The images taken at 10m and during cooler times of the day (dawn and dusk) proved most useful for their study, as the known elevations at which the drones were flown allowed the team to estimate the body size of the nightjars to confirm the species.

“Our preliminary findings demonstrate the potential of drones for surveying nightjars during their breeding season, allowing forestry managers to locate nests more accurately and plan their works adequately. This methodology could also have wider applications, since it could technically be adapted to detect any warm-blooded species,” project supervisor Dr Robert Thomas said.

The thermal images from the drones showed that all the nightjars sat in close proximities throughout the duration of the drone flights, an action these birds do to avoid being detected by predators.

“We don’t know whether the nightjars perceived the drones as a predator. This would be interesting to explore in future studies to ensure that the sight and sound of drones don’t have any negative impacts on the birds’ stress levels or metabolism,” Shewring concluded.

The British Ecological Society annual meeting held in Birmingham on Monday brings together 1,200 ecologists from more than 40 countries to discuss the latest research presented by Mike Shewring.

Last Wednesday, taking inspiration from the way in which birds fold their wings in mid-air, researchers from the University of Zurich announced their development of a foldable drone, capable of fitting through narrow gaps and holes.

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