Effects of age, territoriality and breeding on survival of Bonelli’s Eagle Aquila fasciata

Survival typically contributes most to population trends in long-lived birds and its accurate estimation is therefore vital for population management and conservation. We evaluated the effects of age, territoriality and reproduction on survival in Bonelli’s Eagle Aquila fasciata through multistate capture-mark-recapture analyses on a long-term dataset. Monitoring was carried out in southeast France (1990–2008) and involved the surveying of territorial Eagles, the marking of fledged chicks, and the recording of resightings and recoveries of marked non-territorial and territorial birds. Survival improved with age, but territoriality was not retained in the best model; yearly survival was estimated at 0.479 for fledglings (to 1 year of age), 0.570 for 1- and 2-year-olds, and 0.870 for 3-year-old and older individuals. The second best model supported a further increase in survival from 3-year-olds (0.821) to older individuals (0.880). In the third best supported model, territoriality enhanced survival, but only in 2-year-olds (0.632 vs. 0.562 for non-territorial). We found no correlation between the previous breeding stage and future survival, consistent with the long lifespan of the study species. Nevertheless, 4-year-old and older successful breeders were more likely to breed the following year than failed adult breeders (0.869 vs. 0.582), suggesting that the cost of reproduction is small in comparison with the variation in quality among individuals or their territories.