Sula sula [sul' uh sul' uh]

Description

The smallest member of the booby family is 25-30 inches long, has a wingspan of 35-40 inches, and weighs 31-35 ounces; females are larger than males.

The red-footed booby has strong neck muscles, and a wedge-shaped tail. It has a long, tapering bill with serrated cutting edges to help catch and eat its prey. Its external nostrils are closed to allow for plunge-diving, but it also has secondary nostrils beside the mouth which are automatically covered by flaps when it plunges. The skin around its face is generally bare. The wings are long, pointed, and situated fairly far back on the body. They help the bird to fly in high winds (which it does by alternating powerful flaps with gliding) and also to dive. When diving, the wings close around the body of the bird, making it more aerodynamic. The legs are set far back on the body, helping it to swim.

Red-footed bobbies come in a variety of color variations (morphs): white-tailed brown, white-headed and white-tailed, white (with black on the wings), black-tailed white, and golden white. All have the characteristic red feet and legs and pale blue bill.

Although the red-footed booby can fly for long distances with great ease, take-off is extremely difficult, and the bird relies heavily on the wind to attain flight. Without a breeze, the red-footed booby struggles to take to the air, half-running, half-flying to gather momentum. In the water, the red-footed booby will thrust both feet backwards simultaneously and jump forward into the wind in order to lift off from the surface.

Distribution and Habitat

Red-footed boobies inhabit tropical and sub-tropical waters across the globe. They spend the majority of their life over open sea. Familiar to boaters, they often follow (and sometimes land on) marine craft. When breeding, they inhabit islands and coastal regions in the tropics.

Feeding Habits

Red-footed boobies may spend several days at a time at sea fishing, as far as 93 miles out. Binocular vision allows them to fly higher than other members of their family when searching for food. Once prey are sighted, the bird plunge-dives to moderate depths (up to 98 feet) in order to acquire fish, which it catches and swallows on its return to the surface. Red-footed boobies can also catch prey in midflight, due to their smaller size and better agility than other species of booby. This is a particularly effective method for hunting flying fish as they jump out of the water. They are also known to hunt squid at night, as their large eyes allow for effective nocturnal hunting. Red-footed boobies are communal hunters, and once one bird has spotted food, all will dive.

Reproduction

Red-footed boobies are communal nesters, with hundreds of mating pairs gathering in one location. Breeding and chick-rearing usually lasts from late-January to September. The higher the population density, the more ritualized their courtship behavior. Males show off their red feet and posture with their tails, beaks, and wings facing upward and call for mates. Once a breeding pair is formed, it will return to the same nest year-to-year to mate.

The nest is a large open platform of twigs, lined with grasses or leafy matter. They often build their nests in trees. Their choice of nest location may be a way to avoid competition for space, since other species of boobies nest on the ground.

The single egg (which is pale in color and covered in a chalky residue) is incubated by both parents for 41-45 days. The whitish-brown chick broods on the feet of its parents for the first few days, and is not left unattended until is is approximately one month old, when it can regulate its own body temperature. The fledgling phase lasts from 100-139 days, and post-fledgling care lasts for about 190 days. Juveniles are brown or grayish-brown with yellow-gray legs.

The red-footed booby reaches sexual maturity at 2-3 years, can breed for up to 23 years, and can live for more than 40 years.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Aves
order Pelecaniformes
family Sulidae
genus & species Sula sula

SOURCE
Animal Diversity Web animaldiversity.org/accounts/Sula_sula/

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This page was last updated on June 17, 2017.