Bearded vultures only start breeding after they are 7-8 years in life, often later, and undergo progressive plumage changes throughout the early years.
Monitoring of bearded vultures often requires identification of the age classes, and so understanding the moulting process in this species is necessary. We therefore welcome the publication of a brand new paper describing in detail the moulting of feathers in this species.
Moulting feathers is a time-consuming and energy-demanding task for large birds such as a vulture, as it takes a long time to grow a long feather, and birds cannot tolerate large gaps in the wing, not to lose flight power, so they can only tolerate one or two simultaneously growing feathers. As a consequence, large birds usually take several years to complete a full moult cycle – the bearded Vultures usually need 2–3 years for changing all flight feathers.
In this paper Zuberogoitia et al describe the sequence, extent, and timing of moult of 124 Bearded Vultures in detail. They found that subadults (from 3rd to 5th calendar year) started moulting earlier than adults (early March vs. late April), and that adults moulted more feathers than subadults – while these need 3 years for moulting all flight feathers, the former normally complete it in 2 years.
You can download the paper below.
(Photo VCF/Bruno Berthémy)