We saw many of these birds and tropicbirds during our Atlantic crossing. They used the trampoline on our catamaran as a rest stop. They also learned that they can't do a carrier landing on solar panels. It was funny to watch them come in for a landing and slide right off the back of the boat.

It looks like they feed on flying fish, primarily. These would jump out of the water and skim across the surface for hundreds of meters, and then BAM!, a bird would swoop in and end its existence.