What is the term used to refer to an immature peregrine in British usage?

In British terminology, the term "brown hawk" is often used to refer to an immature or juvenile peregrine falcon. This designation stems from the distinctive plumage of young peregrines, which tend to have a more muted, brownish coloring compared to the adults. The naming convention reflects the bird’s age and developmental stage, helping falconers and ornithologists to categorize and recognize the various life stages of this species.

In contrast, the other terms do not specifically refer to the immature peregrine. "Vagrant hawk" does not pertain to age or development but rather to a bird that strays from its normal range. While "peregrine falcon" is a broader classification that includes all ages of the bird, it does not convey the specific stage of immaturity. Similarly, "young raptor" is a general term for any young bird of prey and lacks the specific reference to the peregrine species. Therefore, "brown hawk" is the most accurate and contextually appropriate term for an immature peregrine in British usage.