Background: Drones are reliable tools for estimating colonial seabird numbers. Although most research has focused on methods of improving the accuracy of bird counts, few studies have evaluated the impacts of these methods on bird behavior. In this study, we examined the effects of the DJI Phantom 3 drone approach (altitude, horizontal and vertical descent speeds) on changes in the intensity of behavioral response of guano birds: guanay cormorants (Phalacrocorax bougainvilli), Peruvian boobies (Sula variegata) and Peruvian pelicans (Pelecanus thagus). The breeding and non-breeding condition was also evaluated. Methods: Eleven locations along the Peruvian coast were visited in 2016-2017. Drone flight tests considered an altitude range from 5 to 80 m from the colony level, a horizontal speed range from 0.5 to 15 m/s, and a vertical descent speed range from 0.5 to 3 m/s. The intensity of th...

This study was supported by Fondo Nacio-nal de Desarrollo Científico, Tecnológico y de Innovación Tecnológica (FONDECYT–Perú) within the ‘‘Proyecto de Mejoramiento y Ampliación de los Servicios del Sistema Nacional de Ciencia, Tecnología e Innovación Tecnológica’’ [contract: 08-2019-FONDE-CYT-BM-INC-INV’’], and by the Programa Nacional de Innovación en Pesca y Acuicul-tura and the Universidad Científica del Sur through the project ‘‘Aves Marinas como Centinelas del Mar: Uso de video-cámaras/ GPS en piqueros para monitorear actividades pesqueras ilícitas en el Perú (PNIPA-PES-SIADE-PP-000169)’’.