Joshua Wilson discusses recent research at Moreton Bay, Australia which saw Wilson and colleagues conduct over 200 drone approaches of shorebird flocks to measure how the birds respond to drones. Particular attention is paid to the critically endangered Eastern Curlew.

Stress responses

Imagine you’re resting in your bed when, out of the corner of your eye, you see something scuttling along the roof towards you. You feel your heart start to race, adrenalin coursing through your veins as you let out a primal scream and leap out of the room. Upon hearing your distress, your house mate in the room next to you, who’s not normally scared by this sort of thing, runs from their room too, shouting “What is it, what’s going on!?”.

You’ve just experienced a stress response that is perhaps similar to that which the critically endangered shorebird, the Eastern Curlew, experiences as it flees from an approaching drone, dragging less jumpy shorebird species along with it.

Drone approaches

Alongside the Queensland Wader Study Group and The Moreton Bay Foundation, we’ve been studying the responses of birds to an approaching drone in the hopes that our research can help inform the regulation of drones near critical bird habitats so that they can rest without constantly being jolted awake by a drone scuttling across the sky.

By conducting over 200 drone approaches of shorebird flocks throughout Moreton Bay in Southeast Queensland, Australia, we began to unveil a detailed picture of how shorebirds respond to drones, how close a drone can be before each species takes flight, and how the shorebirds interact with each other in mixed flocks.

Findings

The most alarming finding from our research was the sensitivity of the critically endangered Eastern Curlew to drone disturbance. We found that, even when we attempted to fly 120 meters above them with a drone just 20 centimetres wide, they were still terrified by the drone and flew away as a result!

The global population of many shorebird species has decreased dramatically in the last 30 years, mainly due to the degradation of their habitat. While it’s unlikely that drone disturbance has contributed much to this decline, we know that, just as our sleep was interrupted in our imagined scenario, disturbance can interrupt birds as they try to rest or feed, and birds avoid habitats that are regularly disturbed, both of which could contribute to population declines.

Drone use has already increased dramatically in the last decade, and this increase is set to continue, leading to concerns that drones may become yet another source of disturbance for birds that are already critically endangered, like the Eastern Curlew.

On the other hand, many species surprised us by how comfortable they were with a drone being flown over them. Most birds were unlikely to fly away when the drone was flown above them, provided it was higher than 60 meters.

This finding paves the way for drones to be used as a valuable conservation tool to survey birds in places that are hard to reach on foot, such as seabirds breeding on inaccessible islands in the South Atlantic Ocean, or penguins nesting on freezing Antarctic outcrops. In some cases, drones can also be more accurate and reduce disturbance compared to traditional ground-based survey methods.

However, in our imagined scenario, your reaction woke and spooked your house mate too and this is exactly what we saw in mixed-species shorebird flocks; when Eastern Curlew took flight, screeching out alarm calls, nearby species, who were not typically sensitivity to drone disturbance, would also flee, perhaps yelling at the Eastern Curlew “What is it, what’s going on!?”. This interaction between species means that drone regulations need to be based on the most sensitive species likely to be present in the habitat.

Recommendations

We recommend that organisations such as the Civil Aviation Safety Authority, and Parks and Wildlife Service regulate drone use near shorebird flocks containing species that are highly sensitive to drone disturbance, like the Eastern Curlew.

We also encourage researchers to consider adding drones to their conservation toolkit but urge them to carefully evaluate the risk of disturbance before conducting drone-based bird surveys. While I’m rarely kept awake at night by things scuttling in my room, I do sometimes lie awake disturbed by the dramatic decline in biodiversity. Hopefully this research can help us introduce measures to mitigate drone disturbance and help us all sleep a little easier.

Read the full article “Drone-induced flight initiation distances for shorebirds in mixed-species flocks” in Journal of Applied Ecology