The European nightjar is a protected species in parts of the UK, so when forestry or construction work is planned to take place in their habitat, ecologists first need to check for nesting sites. A new study suggests that drones could make the task much easier, and do a better job at spotting the birds.
Nightjars are camouflaged to look like tree bark, and they lay their eggs on the ground. Additionally, they stay still when approached, in order to avoid detection. This means that when ecologists are hiking through the woods looking for the birds and their nesting sites, they can very easily be missed. What's more, those workers risk injury when accessing sites where there are many fallen trees on the ground, plus such surveys can be expensive to carry out.
With these limitations in mind, scientists from Cardiff University are looking into using thermal-camera-equipped aerial drones to find the birds.
In a recent pilot study, which was conducted during the nightjar breeding season (between May and August), the drones were used to photograph known nesting sites at the Bryn conifer plantation in South Wales. Thermal photos were taken at dawn, midday and dusk, from altitudes of 10, 20 and 50 meters (33, 66 and 164 ft). Such distances were deemed to be sufficient as to not disturb the animals.
It was found that the drones could easily image the birds, particularly at cooler times of day (dawn and dusk), when the temperature difference between the animals' 40 ºC (104 ºF) bodies and the surrounding environment was the greatest – see the photo below for an example. Additionally, by knowing the altitudes at which the photos were taken (10m worked best), it was possible to ascertain the birds' body size, and thus confirm that they were in fact European nightjars.
Further studies are now being planned, in order to confirm that the drone fly-overs don't cause stress to the birds, which may interpret the aircraft as predators.
"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," says project manager Dr. Robert Thomas. "This methodology could also have wider applications, since it could technically be adapted to detect any warm-blooded species."
PhD student Mike Shewring presented the research this Monday at the British Ecological Society annual meeting.
Source: British Ecological Society
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