Masked Booby Identification

The Four Keys to ID

• Size & Shape

  A heavyset seabird with long, pointed wings, stout neck and head, and fairly long, pointed tail. It has short legs with large, webbed feet. The bill is long, heavy, and daggerlike.

  Relative Size

  Larger than a Great Black-backed Gull, smaller than a Northern Gannet.

  goose-sized or larger

  Measurements

  • Both Sexes
  • • Length: 29.1-33.9 in (74-86 cm)
    • Weight: 45.9-82.9 oz (1300-2350 g)
    • Wingspan: 63.0 in (160 cm)

  © Bruce Wedderburn / Macaulay Library

• Color Pattern

  Adults are white with black wing and tail feathers, yellowish bill, and dark mask at the base of the bill. Birds seen off the U.S. usually have olive legs and feet. Juveniles are white below, dark brown with white feather edging above, with white hindcollar, brownish head, and dull greenish bill. Subadult plumages are mostly white but with brownish flecking, especially in upperwing, head, and rump. They are distinguished from Northern Gannets by black secondary feathers and a black mask.

• Behavior

  Flies high over the ocean and scans for prey, then drops swiftly in a plunge-dive. Breeding birds display enthusiastically, males marching around the females with an exaggerated gait and “sky-pointing” with bills; paired birds touching bills, preening, and watching each other intently.

• Habitat

  Open tropical oceans around the world; nests on the ground on small tropical islands, usually in areas free of vegetation.