Birds of Prey
Even though they are not closely related, I have included hawks, harriers, vultures, and owls in this category. They are all birds of prey (raptors) and Kaufman includes them in his book "Field Guide to Birds of North American".
Eagles and allies
Eagles and Osprey have long, wide, rounded wings for soaring.
Hawk-eagles
Kites
North American kites are not closely related. They do hover.
Accipiters
Accipiters have short broad wings and long tails which gives them movability. They primarily catch/eat other birds.
Buteo and Buteo-like Hawks
Buteos and buteo-like birds have long, wide, rounded wings. This give them the ability to soar.
Harriers
Harriers facial discs help them focus the sounds of rodents. Females are larger than the males and have different coloration than the males.