Nice pic! A buddy in SE New Mexico at 7,000 feet gets both mountain and western bluebirds nesting in his houses every year, sometimes a given nest box alternates between species. Not sure how the birds figure that out, no cross-species pairings tho.

"...if the gentlemen of Virginia shall send us a dozen of their sons, we would take great care in their education, instruct them in all we know, and make men of them." Canasatego 1744