Who Are You?

I'm not sure which type of hummingbird this was - the shortish bill, green flanks and purplish throat narrows the list, but I'm struggling beyond that. I'm assuming this is an immature bird (although it seems early for that). I know that the orange on the head and throat is most likely pollen, so that's no help. Anyone better with hummer IDs willing to help?

Seen in Florida Canyon, AZ in early May.

update: This is possibly a first summer Costa's Hummingbird (male). Still waiting for confirmation.