This is a tough one. There is more than one bird that looks like this and my research reveals that a lot of people have a tough time identifying these type of birds. After looking at my field guide, eliminating some possibilities based on TRNWR's bird list and searching the web, I decided that this is a Western Wood-Pewee. The breast coloration, high crest, a lack of eye ring and wing bars seem to be most consistent with the Pewee. Another possibility could be a Olive-sided Flycatcher, but most pictures I saw of it had darker coloration on the sides of its breast. It definitely exhibited the Pewee/Flycatcher behavior of sitting on a branch, flying out to catch a flying insect and then returning back to the branch.