Data from: Balancing moult, migration, and breeding in a long-lived partially migrant raptor

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 those 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.