I went to the county park today to look for birds to photograph. After about half an hour, I noticed a pair of grackles (and not purple martins as I wrote previously) in the midst of a courtship ritual. The male, shiny and bluish purple, was placing some food into the open beak of the brown female. This is what some male birds do to convince a potential mate that they are up to the task of taking care of her and their future brood.
This may be the same couple a few minutes later.
Last week, I also saw the same behavior with our backyard cardinals. A female cardinal kept fluttering her wings while perched over a bowl of sunflower seeds that I had put out on our deck. At first I thought she was sick or in distress, as she would not eat anything. Then a red male cardinal swooped in, picked a seed and placed it in her beak. He did it twice again. I ran to get my camera, but by the time I came back the pair had flown away.