Classification Until  the recent use of phylogenomics to classify bird families, all raptors had commonly been grouped into 5 families belonging to the order “Falconiformes”. Genome-based cladistics however yielded the surprising demonstration that Falconidae, including falcons and caracaras, are closely related to passerines (and parrots), while the other 4 families do not share a recent common ancestor with Falconidae. The latter were therefore treated as the only family of the order Falconiformes and the other 4 raptor families  were moved to the new order Accipitriformes.

Falconiforms comprise about 64 species of diurnal birds of prey. They have comparatively sharply pointed wings, sharply curved talons and usually a notch, or tooth, in the upper bill. 

The subfamily Herpetotherinae contains the rather primitive Laughing Falcon and 7 other forest falcons. They live largely on reptiles.

The subfamily Polyborinae stand at the top ot the pecking order among the New World scavengers and  will drive vultures away from the meal. They include the 10 Caracaras ranging from Florida to South America; the Crested Caracara is the national bird of Mexico. They spend much time on the ground and feed largely on carrion.

The 8 subfamily Poliohieracinae species, called pigmy falcons or falconets, hunt insects much like flycatchers.

Finally, the subfamily Falconinae contains the 38 true falcon species. Among these, the Peregrine Falcon, whose drives at 175 miles per hour, recorded by pursuing airplanes, often result in a mortal strike on the prey;  the American Kestrel, shown here in the West Indies, capturing a lizzard; and the Merlin, which is the smallest of the Falconinae, seen at right in Iceland. 

Hackett SJ et al (2008): Phylogenomic Study of Birds

Austin Jr, O.L. (1961): Birds of the World, Golden Press, New York