Every year, as winter descends on North America, thousands of humans cast an eye toward the Caribbean, with its sunny islands and warm waters, as they plan an escape south. They are following in the flight path of thousands of birds. Since Holland America Line purchased Half Moon Cay, it has functioned as a nature reserve—only 22 hectares (55 acres) of the island's 971 hectares (2,400 acres) have been developed. Bird-watching enthusiasts have a chance to spot a diversity of species that have learned not to fear humans. Some 48 species have been recorded on a comprehensive bird list for the island, with terns, pintails and petrels among the most common.