What is a notable trait of American kestrels in terms of plumage?

American kestrels are known for being sexually dimorphic, which means that males and females exhibit different plumage characteristics. Male American kestrels typically have more vivid and bright coloration, such as bluish-gray wings and a rufous-colored back, while females generally have a more subdued coloration, featuring more browns and streaks. This distinct difference in appearance not only aids in identification of the sexes but also plays a role in mating behaviors and territorial displays.

In contrast, the other options do not accurately reflect the characteristics of American kestrels. For instance, stating that they do not exhibit plumage dimorphism overlooks the clear differences between male and female birds. Saying that the plumage is uniform among all ages inaccurately implies that juvenile birds would appear the same as adults, which is not true as juveniles often have different markings and colors. Lastly, claiming they have a non-distinct plumage does not acknowledge the vibrant coloration that both sexes can display, thus failing to recognize the striking differences that are present.