Medium sized hummingbird. Mostly green with white chest and collar. Red throat on the males. The females are a paler green with light colored throat to belly. The females may get tawny flanks. White patch behind the eyes. Tail feathers longer and wider then some of the other hummingbirds. Sound louder and almost machine like.
They summer in the high elevations and winter toward Mexico. They are pretty wide spread across this part of Colorado. I noticed they like conifers.