Pigeon Hawk. Of course, it is now known as Merlin (Falco columbarius).
The usual Merlin we have here is the paler 'Prairie' (F. c. richardsonii). However, this one looks more like a 'Taiga' (F.c. columbarius) to me; such as one that might have been farther North for the breeding season and is now heading South. Some Merlins are Neotropical migrants; the Prairie type is a year-round resident here (at least in my town as per previous blog posts here and here)
It was eating a large blue dragonfly just before I got my camera lined up. Smaller birds are usually the main food source.
Cool Fact from All About Birds
The Merlin does not build a nest, but instead takes over old nests of other raptors or crows. It sometimes nests on top of domed magpie nests rather than in the nest cavity.
For more information and audio clip, go to All About Birds