I was at the side yard, opening the gate to put away my mower when two of the largest bees I've ever encountered flew out from inside a knothole in the lower portion of the 4"X4" post. They weren't too aggressive, simply floated at my eye level and watched me until they'd decided I wasn't a threat. One was blonde, the other black. Judging by what I've found through google, the blonde is a male and the black female.
Many thanks.
The Ranger