Field study
The drone proved to be a useful tool for safely studying colonial and gregarious waterbirds: their flocks were counted in more than 96% of cases. It also turned out to be minimally invasive: out of 343 birds / missions, no dangerous event was recorded, such as a collision of a bird with the drone or a permanent nest abandonment as a result of a bird being scared away. A similar conclusion was reached during research conducted in Australia based on 97 flight hours (Lyons et al. 2018). The strongest reactions to the presence of the drone were displayed byAnser geese in the non-breeding period, mainly large flocks foraging on farmland. Similar results were obtained in Scotland, where, in addition, a dependence on flock size was demonstrated: the larger the flock, the greater the chance of its responding to a drone (Jarrett et al. 2020). Our results indicate that the group of birds reacting adversely to the drone was slightly larger than that exhibiting a moderate reaction or none at all. Birds in the non-breeding period reacted more strongly to the drone’s appearance – 18.8% of adverse reactions. Breeding birds, on the other hand, appeared to be indifferent to the drone, undesirable behaviour being manifested in only 3 (3.6%) cases out of 83. Chabot et al. (2015) drew similar conclusions during their study in a Common Tern colony. In our case, however, these undesirable behaviours (observed in Black Tern) involved attempts to attack the drone. This is potentially more dangerous than when the birds are scared away over a long distance, as a bird-drone collision may ensue; drone attack behaviour has been reported in Australia (Lyons et al. 2018). Despite the positive results of this study, and the effectiveness and minimal invasiveness of the drone, the use of a drone for performing bird counts should be approached with great caution. The persons conducting the research must have a good knowledge of the study area, so that in the event of an emergency, the drone can be landed quickly. They must also be experienced in bird biology and behaviour in order to be able to predict and prevent dangerous situations.
The flushing of birds even at a long distance – behaviour No. 3 in this study, defined as unacceptable – may not have a significant effect on them, as they will probably return to the site after some time. But the effect of repeated drone flights may well be different, as this can lead to the permanent abandonment of a site. Therefore, the frequent flying of large numbers of drones over flocks of birds for recreational purposes should be proscribed. Drones are becoming more and more affordable (Kyrkou et al. 2019), and the temptation for people to ”play” with birds will have a decidedly negative impact on the latter.
The present study was conducted by a person with 30 years of experience in field ornithology, so his ability to predict bird behaviour will have helped to avoid dangerous situations. At the present stage, of course, these are still speculations, but it is highly probable that people with less experience will pose a greater risk of dangerous situations for animals and other humans. Hence, the use of drones in wildlife research should be legally regulated: a license should be issued for such work, and the persons involved should have passed an examination in animal biology and behaviour.