Cabot's Tern, above in its winter plumage, is native to North America and the Caribbean.
In summer breeding plumage it has a fully dark cap.
Cabot's Tern looks similar to the Sandwich Tern, of which it was classed as a subspecies until recently.
The Sandwich has a narrower bill and some plumage differences and is only a rare vagrant to the Americas.
Cabot's has a subspecies called the Cayenne Tern in northern South America.
A juvenile Cabot's. Photos on this page were taken by Alexandra Makhnina.
She says that this juvenile was constantly begging its parent for food.
The related Royal Tern, shown alongside a Cabot's (and Laughing Gulls) in the third photo above, is much larger and has an orange bill.