The first year: movements and survival of juvenile Montagu’s Harriers (Circus pygargus) in the Spanish Extremadura

Understanding the movements and mortality of individuals across different life stages is crucial for the effective conservation of wild populations. So far, information about movements came predominantly from adult animals. Here, we tagged 30 juveniles of Montagu’s Harrier with GPS transmitters in La Serena, a core area for Montagu’s Harrier in Southwest Spain. With the data obtained we studied dependency period, pre-migratory (exploratory) movements, migration routes, movements in Africa and mortality at each stage. Our results show that early and late laying females lead to differences in the length of dependency and pre-migratory period of the chicks, though migration start was not affected at the end of August, beginning of September to Sub-Saharan Africa. Mortality rate was highest during dependency and pre-migratory period. After spring migration, at least 5 out of 8 returning individuals (3 females, 2 males) started a breeding attempt whereas 2 males continued exploring flights, but finally stayed most of the time in the breeding area of their first year. Stages of the first year’s exploratory pre-migratory flights were not relevant for choosing a breeding site in the following year.