The Red-shouldered Hawk is a close relative of the Red-tailed Hawk. They occupy a similar ecological niche except where the Red-tailed Hawk is found across all of North America, the Red-shouldered Hawk is only found in the eastern half. Personally, I have noticed that in general, the Red-shouldered Hawk prefers forested areas while the Red-tailed Hawk will be found more often in open fields. However, I haven’t seen any official sources discussing that trend so I don’t know if that holds true across the whole species or if it is only true of my area (or I may have some sort of sampling bias).
Crayshack 