This cormorant was doing its mating display behavior, which it was carrying out sitting in an empty nest. Since all of the other nests appeared to have eggs and hatched young, all this displaying may well have been in vane. It did give a good view of this behavior and its blue skin area which is distinctive of breeding readiness.
This cormorant was one of several in a nesting colony on the cliffs over La Jolla Cove in the San Diego area. This year the birds were nesting much closer to the sidewalk walkway along the cliffs, giving much closer views than in recent past years. Most of them had three young in the nests, although some were still sitting on eggs.