Frigatebirds are remarkable for being capable of staying in flight for several days and nights, and may even sleep while on the wing. Like other frigatebirds, this species uses thermals to soar to heights of up to 2,500 metres, gliding downwards and climbing again in succession, with little need for wing flapping. This effortless flight allows long distances to be covered with minimal energetic cost (4).
The lack of waterproof plumage means that this species obtains most of its prey either just above, floating on, or submerged a few centimetres below the water surface. As such, its main source of prey is flying fish (airborne or just beneath the surface), but it also takes squid, jellyfish and scraps discarded by boats, and will often feed over tuna and other predatory fish that drive smaller fish species to the surface (2) (3). In addition to catching prey, the lesser frigatebird will sometimes harass other bird species on the wing, forcing them to release food that they have recently caught, which is then snatched from mid-air before it reaches the water (2) (3). When not airborne, the lesser frigatebird perches in trees, bushes or, less preferably, on the ground. A gregarious species, roosting takes place in large groups, where, during the day, individuals may display a remarkable sunning posture, involving sitting upright with the wing undersides rotated upwards while extended to the sides, exposing the chest and underwings to the sun (3).
The breeding behaviour of the lesser frigatebird is highly unusual and dramatic. During courtship, males gather in groups of various sizes, with gular pouches inflated, bills clattering, and wings and heads waving, while calling to attract females flying overhead. Once a pair decides to mate, they snake necks together and nibble at each others feathers, before commencing the construction of a nest. The male provides material such as twigs, while the female does the actual building. Both birds defend the nest from intruders or theft of nesting material by other males (3). After mating, a single white egg is laid, which is incubated for around 46 days by both the male and female. The chick, which takes 20 to 24 weeks to fledge from the nest, is tended to and fed by both sexes for a further four to six months (2). This extended period of parental care exhibited by all frigatebirds is the longest of all birds, and means that a pair can only breed in alternate years. However, despite this intense level of parent care, many chicks starve to death within months of becoming fully independent because they do not learn to feed themselves (3). Furthermore, some areas in which the lesser frigatebird nests are severely affected by the occurrance of El Niño evnts, during which many young starve to death as the local fish move elsewhere and good fishing skills become even more important (6).