Moult, breeding, and migration are the three major life‐history events in the annual cycle of birds. All are energetically demanding processes that rarely overlap. In large raptors such as the Egyptian vulture Neophron percnopterus , completing a full moult may take more than one year, requiring birds to balance this process with other life‐cycle events. We analysed 740 moult cards from across the species' distribution, including migratory, sedentary and mixed subpopulations, to test predictions about trade‐offs between the physiological demands of migration and moult. Juveniles began moulting in January–February of their second calendar year and continued ‘year‐round' until their fifth calendar year. Adults, however, suspended moult from the months preceding spring migration until the late breeding phase. Subadults from the Canary Islands started moulting earlier and completed it faster than those from western Europe, while adults from western Europe initiated moult later than adults from the Canary Islands, India, and Oman. Sedentary subpopulations, particularly that from the Canary Islands, showed a greater moult extent and replaced more primaries annually than migratory and mixed subpopulations, whereas the wintering subpopulation of southwestern Spain (Extremadura) exhibited the smallest moult extent. Moult symmetry decreased from the second plumage onwards and differed between the Canary Islands and Oman subpopulations. Geographic differences in moulting patterns likely arise from population‐specific life‐history trade‐offs, reflecting local adaptations or responses to environmental constraints. These patterns highlight the influence of migratory strategy on moult progression and suggest that sedentary lifestyles may allow more extensive feather renewal in long‐lived raptors.
Zuberogoitia et al. (Sun,) studied this question.