While I was at Great Gull Island, New York, July 3-5, two different Peregrine Falcons were passing through the tern colony. I never saw one catch a tern, but they were definitely hunting as they rocketed over the island low and fast with about a hundred screaming terns right behind, then turned and made another pass. After a few passes over different parts of the island the falcon would leave and fly out across the water, returning a few hours later to try again.
I managed a few photos of one of these hunting excursions. In looking at my photos I confirmed something I thought I had noticed – there were no Roseate Terns among the group harassing the falcon, only Common Terns. This is true to their nature, Roseates have a reputation for being less aggressive than the Common Terns, but I had never considered how that might extend to predators. When a Great Black-backed Gull flies by the island the terns sound the alarm and escort it away from the colony, but I had never paused to think that it might be only Common Terns that do this.
And if that’s true, it brings up the question of whether a Roseate Tern nesting colony can be successful in this region without Common Terns for protection.