Center of interest for the male bluebird is the female who is checking out the available nest boxes.
Anytime you are around bluebird nest boxes in the spring, there is a conflict with the ever- present tree swallows, that greatly outnumber them. So, the bluebirds often take up a perch on a box and withstand the fly-bys from their antagonist. I've seen the male bluebird spread his wings to appear larger in face of the harassment. Yesterday, I saw a new behavior as the pair stood together with some degree of solidarity.
I mentioned a second meaning to "bluebird days" relating to the sky color. So, as I was photographing the birds, I became aware of an unusual aircraft sound. It approached slowly with a broad seemingly widespread rumble. I realized it was directly overhead and looked up to see this. The sky really was close to the bluebird color.
It was a KC-10 wide body Air Force tanker with six A-10 Warthog fighters at a modest altitude performing a refueling exercise. (The KC-10 is a modified DC-10.) In a few seconds, one of A-10s moved into position under the tail of the tanker. The muffled sound I was hearing was the combined noise from fifteen engines.
In my previous blog, I noted to expect the unexpected. So true.