Pair Of Masked Boobies
This pair of masked boobies is considering nesting on Trig Island within the French Frigate Shoals (Kanemiloha'i), part of the Hawaiian Islands National Wildlife Refuge and the Papahanaumokuakea Marine National Monument. La Perouse Pinnacle can be seen in the background behind the birds. Although very similar, male and female birds can be distinguished by their size (females are usually larger), coloration (the bill and legs of males are usually more yellow), and voice (females emit a "honk", while males produce a squeaky, whistle-like call). Males often attract females with a stretched-neck sky-pointing display and by offering “gifts” of feathers, pebbles, or anything else that he deems necessary to win her heart.
Image credit: Lindsey Kramer/U.S. Fish and Wildlife Service