Which of these birds does not show distinctive "immature" plumage during its first year?

The American Kestrel is known for its relatively consistent plumage throughout its first year, unlike some other species that exhibit a clearly distinct "immature" phase. Kestrels have a more uniform appearance as juveniles, lacking the stark plumage differences found in species like the Goshawk, Red-tailed Hawk, or Merlin.

In contrast, these other birds develop juvenile plumage that can look markedly different from their adult forms. For example, immature Goshawks tend to have more mottled feathers, while Red-tailed Hawks display a distinct color variation as their maturity progresses. Merlins, too, show significant differences in their plumage that can help in identifying their age. This consistency in the juvenile plumage of the American Kestrel makes it unique among the choices provided.