This is the order Accipitriformes. These are the diurnal (or daytime) birds of prey. They are the raptors, and hunt dawn/dusk and throughout the day.
The characteristics of the order include having a sharply hooked beak, strong legs and feet. They have the typical raptorial claws, with the hind claws being opposable.
They are exceptionally long-lived birds, to where the young take anywhere from a year to five years to reach sexual maturity. Due to these two factors, they also have a very low reproductive rate.
In terms of the number of species within the order, it currently sits at 255 species, within 74 genera, in three different families. The largest family is Accipitridae, as the other two families consist of a single species. Geographically, they are found worldwide (with the exception of Antarctica), and can be found in a variety of habitats such as the desert, tundra, forests, wetlands, and rainforests.
The three families include:
Accipitridae (Hawks, Eagles, Kites, Harriers, and Old World Vultures)
Of the three families, the only two with members that can be found global are Accipitridae and Pandionidae, the third family (Sagittariidae) is found only in Africa.
So therefore members of the families that can be spotted within the United States, Canada, and Mexico include:
Common Black Hawk
Other members of the family Accipitridae (including Old World vultures) are found elsewhere globally.
Photography goals for this order include: getting a picture of the secretarybird in the wild (meaning a trip to Africa), and then trying to get a picture of a member of the Accipitridae family from each of the other continents (South America, Africa, Europe, Asia, and Australia). Another goal (or two) would include getting a picture of as many members of the Accipitridae family within the US as I could, plus maybe getting a few pictures of fledglings/immature adults as well.