Drones may revolutionize the way researchers monitor wildlife, according to a new Scientific Reports study. In both tropical and polar environments, unmanned aerial vehicles (UAVs) are more precise than traditional ground counts for determining the size of nesting bird colonies. They can also survey hard-to-reach (and possibly threatened) populations without startling the subjects.  

In their short history, drones have already been used for environmental research, from monitoring breeding success of canopy-nesting birds to surveying elephants in Burkina Faso. But how accurate are they for estimating population sizes? In the wild, it’s nearly impossible to obtain a true population size – there’s just no way to directly count every animal. When conducting population estimates the traditional way, human counters on the ground often face a difficult vantage (pictured below).  

So, a team led by Jarrod Hodgson from the University of Adelaide compared the precision of UAV counts with ground-based counts made concurrently. They studied three types of seabirds in Australia: lesser frigatebirds (Fregata ariel), crested terns (Thalasseus bergii), and royal penguins (Eudyptes schlegeli). Five frigatebird and two tern colonies were sampled at tropical islands in the Ashmore Reef Commonwealth Marine Reserve, and the other tern colony was on nearby Adele Island. The three penguin colonies were sampled at subantarctic Macquarie Island. Frigatebirds nest on the ground among vegetation, terns nest on un-vegetated, sandy shorelines, and penguins are situated on a bare soil substrate.

^{The difficult vantage that human ground counters face when estimating the number of crested terns in a nesting colony. Jarrod Hodgson}

Ground counters used tripod-mounted spotting scopes, binoculars, and the naked eye. Meanwhile, a small, off-the-shelf octocopter and a custom flying wing conservation drone were used to photograph tropical and polar colonies, respectively. An image taken using a digital SLR camera on a drone is pictured below, and you can click here for more stunning views captured by UAVs. 

The UAV-derived counts of colony nesting birds are an order of magnitude more precise than traditional ground counts. Counts using drones were consistently larger than ground counts for frigatebirds and penguins, though there wasn’t a huge difference between the two methods for terns. 

The downward-facing perspective of UAV imagery reduces the likelihood of missed counts due to the terrain as well as birds who might block part of the counters’ line of sight. Additionally, the drone flights didn’t startle the birds, and with still images on the computer, counters get to zoom in on the birds better. Not to mention, with photographs, counts can be completed over multiple sittings. 

^{UAV-image derived counts of this colony of molting royal penguins were significantly larger than ground counts. Jarrod Hodgson}