Monitoring active Osprey nests with drones is more time-efficient and less disturbing than conventional methods

Drones are used to monitor bird nesting sites at less accessible
locations, such as on cliffs, human infrastructure, or within the tree
canopy. While there are a growing number of studies documenting avian
behavioral responses to various drones, there is a continued need to
monitor taxa-specific responses to different drone models. We explored
both the time efficiency and impact of different nest survey methods
(drones, nest climbing, and observations from a bucket truck) and
different drone model sizes (small, medium, large) on the nest defense
behavior of breeding Ospreys. We conducted 166 surveys (126 drone, 25
climbing, 15 bucket truck) at 85 active nests across three nesting stages.
We found variation in 4 of 6 pre-defined behavioral categories, namely for
calling, flying, at nest, and perching behaviors with survey method, sex,
and nest stage. Females were more responsive to all survey methods
compared to males and engaged in nest-protection behaviors most frequently
during incubation. Ospreys spent greater time at their nests during drone
surveys compared to other methods. Agitated calling and flying were also
less frequent during drone surveys. We recorded defensive behaviors across
all survey types and there were no strikes on drones or researchers. Drone
size appeared to influence behavior, with female Ospreys spending, on
average, 18% of survey time calling when surveyed with medium-sized drone
compared to smaller (8%) or larger (6%) models. Surveys with drones took
less time to complete compared to the other methods tested. Based on our
findings, drones appear to be the best choice for monitoring Osprey nests
as they are adaptable, time efficient, and result in less apparent
disturbance to nesting Ospreys than other methods tested. Our research
aids in setting best practices, optimizing drone size, and developing
evidence-driven approaches for monitoring avian nests across a variety of
landscapes and contexts.