A black, raven-sized raptor with a white band at the base of the tail and chestnut colored upper shoulders best describes a . . .

The description refers to a black, raven-sized raptor characterized by a white band at the base of the tail and chestnut-colored upper shoulders. Harris's hawk fits this description well. This species is known for its distinctive coloration and size, which is often compared to that of a raven, especially when seen in flight. The white band at the tail and the chestnut coloring on the shoulders are key identifying features that make Harris's hawk stand out among other raptors.

Conversely, the other species listed do not exhibit this specific combination of traits. Cooper's hawk, while a member of the same family, has a more elongated body and lacks the unique color pattern described. The red-shouldered hawk has a reddish breast and different tail patterns that do not match the description given. The broad-winged hawk is typically larger and features different markings, including variations in its underparts that do not align with the described characteristics. Thus, understanding the specific physical traits of raptors is crucial for accurate identification, and in this case, Harris's hawk is the correct answer based on the provided details.