2.3. Tracing honey-buzzard nests and installation of trail-cameras
in the nests
The forest patches at the study area have been surveyed systematically
for four years (2018-2021) to find all
honey-buzzard nests (Rebolloet al. 2023). We installed trail-cameras in 24 nests of
honey-buzzards: 5 in 2018, 4 in 2019, 6 in 2020 and 9 in 2021. The
cameras (Browning SPEC OPS and SPEC OPS EDGE) were connected to an extra
battery to ensure they could cover the whole breeding period. Cameras
were placed in the surrounding branches at 1.5–2 m from the nest and
programmed to take only one picture when triggered, with a delay of 20
seconds between pictures. Accessing to the nest and installation of
trail-cameras was performed once the nestlings were 16 days old, moment
in which they can thermoregulate by themselves.
At the time of trail-camera installation we estimated the breeding
phenology from the age of nestlings, based on the length of the wing and
body mass (Bijlsma 1997). Laying dates were estimated by subtracting the
incubation time of a single egg (35 days) from the hatching date of the
oldest nestling in each nest (Roberts et al . 1999). Laying
phenology was estimated in julian days, with January
1st defined as day 1.