I remember a few years ago in Yuma, AZ when a dove built her nest on the ladder. I had to move on but this time there were no babies, just eggs. When I began to remove he nest I was surprised that mama dove remained sitting on the nest while I proceeded with removal. She flew off moments later.
In this latest episode with the sparrows I was surprised that all that wind turbulence caused by towing didn't force the babies out of the pin box. Evidently the pin box provided good protection against such an eventuality.