In addition to taking aerial photographs or delivering packages, drones are now being used for a totally new purpose – counting small birds!
A recent study from The Auk: Ornithological Advances tests this new technique to monitor wildlife and concludes that regardless of certain drawbacks, the technique has the potential to become a key tool for land managers and ecologists.
Bird surveys offer vital data for environmental management, but they have a few hurdles such as some areas being difficult to reach, and surveyors differ in their skills of identifying birds. Making use of audio recordings made captured by unmanned aerial vehicles (UAVs) can help to resolve both of these hurdles, as hard-to-reach areas can be flown over and a number of people can analysis the resulting recordings.
Andrew Wilson of Gettysburg College and his colleagues tested the viability of this technique by using fishing line to hang an audio recorder from a basic "drone," initially in trial runs across college athletic fields, and then in real bird surveys across Pennsylvania State Game Lands.
The experiments carried out on state game lands directly compared UAV data with traditional ground-based surveys of the same areas. It was noticed that some bird species such as Mourning Doves and Gray Catbirds, were undercounted by the UAV method.
The reason was that the Mourning Doves had very low-frequency calls which did not get picked up by the recorder, and the Gray Catbirds had such high densities calls that it was hard to count individual birds in the recordings. On the whole, however, there were few major differences between the results produced by the two techniques.
The inspiration for the study came while I was surveying forests in the Appalachian Mountain in Pennsylvania for Cerulean Warblers. All of our survey work was done from roadsides or hiking trails, for logistical reasons and to maximize survey efficiency, but I was always aware that our sample locations were very biased and that we were missing key areas such as steep forested slopes.
Andrew Wilson, Gettysburg College
He observes that the audio recorder and the drone used in this study were inexpensive, commercially available models, making this method easily feasible even for those with less funding.
I recall my vocal reaction upon hearing their oral presentation during a session I chaired on emerging technologies to study birds at the 2016 North American Ornithology Conference last August, where I exclaimed, 'What an amazingly simplistic but useful application of a drone for bird research--I wish I had thought of it!' This unique study provides a significant first step toward the inevitable common use of unmanned vehicle systems for monitoring songbird populations both during the breeding season and on migration.
David Bird, McGill University