Abstract
Drones are now widely used to study wildlife, but their application in the study of bioacoustics is limited. Drones can be used to collect data on bird vocalizations, but an ongoing concern is that noise from drones could change bird vocalization behavior. To test for behavioral impact, we conducted an experiment using 30 sound localization arrays to track the song output of 7 songbird species before, during, and after a 3 min flight of a small quadcopter drone hovering 48 m above ground level. We analyzed 8303 song bouts, of which 2285, from 184 individual birds were within 50 m of the array centers. We used linear mixed effect models to assess whether patterns in bird song output could be attributed to the drone’s presence. We found no evidence of any effect of the drone on five species: American Robin Turdus migratorius, Common Yellowthroat Geothlypis trichas, Field Sparrow Spizella pusilla, Song Sparrow Melospiza melodia, and Indigo Bunting Passerina cyanea. However, we found a substantial decrease in Yellow Warbler Setophaga petechia song detections during the 3 min drone hover; there was an 81% drop in detections in the third minute (Wald test, p < 0.001) compared with before the drone’s introduction. By contrast, the number of singing Northern Cardinal Cardinalis cardinalis increased when the drone was overhead and remained almost five-fold higher for 4 min after the drone departed (p < 0.001). Further, we found an increase in cardinal contact/alarm calls when the drone was overhead, with the elevated calling rate lasting for 2 min after the drone departed (p < 0.001). Our study suggests that the responses of songbirds to drones may be species-specific, an important consideration when proposing the use of drones in avian studies. We note that recent advances in drone technology have resulted in much quieter drones, which makes us hopeful that the impact that we detected could be greatly reduced.
Highlights
Drones, or Unoccupied Aircraft Systems (UASs), are well-established tools in field ecology, especially for the purposes of mapping habitats or counting and tracking megafauna [1,2,3,4]
We focused our data analysis on seven songbird species that were known to be present on the site in moderate to high densities: American Robin Turdus migratorius, Yellow Warbler
We manually measured time differences between the four recordings because we found that using a sound correlator [18] led to some spurious results, which we attribute to the temporally overlapping songs of multiple species or individuals, and potentially to erroneous correlation between drone noise detected at the four Automated Recording Unit (ARU)
Summary
Unoccupied Aircraft Systems (UASs), are well-established tools in field ecology, especially for the purposes of mapping habitats or counting and tracking megafauna [1,2,3,4]. Drones have proven to be effective tools for conducting aerial surveys of large birds, especially those found in open habitats [5,6] or that nest or roost in tree canopies [7,8]. There have been few studies that show drones to be useful for monitoring small birds, or those that inhabit dense vegetation, where the reach of aerial imagery is limited. There have been many studies that investigate the impacts of drones on wildlife. A review of these concluded that smaller drones, flown at greater heights, and spending reduced time overhead, were less likely to elicit a response in studied organisms [16]. There are still many unknown impacts of drones, especially on non-target organisms
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
