I saw these beauties while watching the sunrise off Pompano Beach in South Florida.
Unfortunately, the Merlin Bird ID app did not help me identify them right away. So I dug into other references, finding hits in All About Birds, Audubon, and Birds of Southwest Florida.
They are Black Skimmers.
It was incredible watching them soaring back and forth across the beach, the entire flock moving as one, finally settling a few yards from where I was standing.
The pigeon landed in the foreground just as I was taking the picture.