Potential negative effects of the installation of video surveillance cameras in raptors' nests

Video surveillance cameras installed on birds' nests are a cost-effective tool to study many aspects of ecology and behaviour that would otherwise be practically impossible to obtain. However, although most studies report neutral effects of cameras on birds, very few studies analyse in detail the potential negative effects of their use, particularly on raptors. Here, using a long-term database of a population of Bonelli's eagle (Aquila fasciata) collected from 2000 to 2022, I show how the inappropriate use of video surveillance cameras could result in negative effects on the reproduction of a threatened species through a before-and-after control-impact study design. Pairs under video surveillance showed lower productivity, lower breeding success and unusual delayed laying dates. The installation of cameras close to the laying date, coinciding with the mating phase of individuals, most of them subadult inexperienced birds; in combination to the reiteration of visits to the nests once the cameras were installed to check the system, particularly during the incubation period and early stages of breeding; and the installation of cameras in a particular area subject to constant human disturbance, might explain these results. Potential management actions to mitigate the effect of the installation of video cameras on birds' behaviour should include the need to plan the intervention dates, testing the systems beforehand under controlled conditions and adequate post-installation monitoring to avoid unnecessary disturbance to animals. Finally, I urge the scientific community to report the potential negative effects observed in their studies, especially if the target species are threatened with extinction.