What does 'hard-penned' refer to in young birds of prey?

The term 'hard-penned' in relation to young birds of prey specifically means that the feathers are fully grown and developed. At this stage, the feathers have matured and are not only present but also strong and capable of supporting the bird's flight. This is an important phase in a bird's development, as fully formed feathers are crucial for the bird's ability to fly efficiently, hunt, and evade predators.

Other stages of feather development, such as being just starting to grow in or still being in the egg, do not fit the definition of 'hard-penned.' Similarly, while molting is a natural process for birds, it pertains to the shedding of feathers rather than the condition of being fully feathered, making it irrelevant to the definition of 'hard-penned.' Understanding this term is vital for falconers and those studying ornithology, as it indicates the readiness of a bird for activities related to flight, training, and potential hunting.