Variability in spatial behaviour and migratory strategies selection: the case of the Hen Harrier at the southern limit of its distribution

Understanding species' movements and behavioural ecology after the breeding season is crucial to improving conservation efforts. This study investigates the post‐breeding movements of Hen Harriers ( Circus cyaneus ) using GPS/GSM data from 30 individuals over 54 periods from 2019 to 2023. Using maximum and mean distances from the reproductive centroid as a behavioural proxy, we classified post‐breeding movements into three strategies: migration (22.2%), sedentarism (9.3%), and sedentarism with post‐breeding movements (68.5%). Our results challenge the previous assumptions that most of the Spanish Hen Harrier population was sedentary. The study shows a relationship between distance travelled and latitude of breeding areas, suggesting environmental adaptation. The Spanish Hen Harrier population, being at the southern limit of its breeding range, exhibits less pronounced differences between sexes or strategies. Raptors that migrate extensively may be more vulnerable due to a reduction of the area available for post‐breeding movements.