Frégate superbe

Identification

The magnificent frigatebird is the largest species of frigatebird. It measures 89–114 cm (2 ft 11 in – 3 ft 9 in) in length, has a wingspan of 2.17–2.44 m (7 ft 1 in – 8 ft 0 in) and weighs 1.1–1.59 kilograms (2 lb 7 oz – 3 lb 8 oz). Males are all-black with a scarlet throat pouch that is inflated like a balloon in the breeding season. Although the feathers are black, the scapular feathers produce a purple iridescence when they reflect sunlight, in contrast to the male great frigatebird's green sheen. Females are black but have a white breast and lower neck sides, a brown band on the wings, and a blue eye-ring that is diagnostic of the female of the species. Immature birds have a white head and underparts.<p>This species is very similar to the other frigatebirds and is similarly sized to all but the lesser frigatebird. However, it lacks a white axillary spur, and juveniles show a distinctive diamond-shaped belly patch. The magnificent frigatebird is silent in flight, but makes various rattling sounds at its nest.<p>It spends days and nights on the wing, with an average flapping rate of 2.84 beat per second, ground speed of 10 km/h (6.2 mph), covering up to 223 km (139 mi) before landing. They alternately climb in thermals, to altitudes occasionally as high as 2,500 m (8,200 ft), and descend to near the sea surface.

Taxonomie

The magnificent frigatebird was originally considered to belong to the species Fregata aquila but in 1914 the Australian ornithologist Gregory Mathews proposed that the magnificent frigatebird should be considered as a separate species with the binomial name Fregata magnificens. Of the four other species within the genus Fregata, genetic analysis has shown that the magnificent frigatebird is most closely related to the Ascension frigatebird (Fregata aquila).<p>There are two subspecies:<p>Prior to 2022, both these subspecies were considered synonymous with one another and grouped under F. m. magnificens. However, they were split by the International Ornithological Congress in 2022 based on a 2011 study which examined genetic and morphological variation in magnificent frigatebirds, finding both expected and also highly unexpected results. As predicted by the flight capacity of the species, the authors found signatures of high gene flow across most of the distribution range. This included evidence of recent gene flow among Pacific and Atlantic localities, likely across the Isthmus of Panama. This geological formation is a strong barrier to movement in most tropical seabirds. However, the same study also found that the magnificent frigatebird on the Galápagos Islands is genetically and morphologically distinct. Based on this study, the Galápagos population has not been exchanging any genes with their mainland counterparts for several hundred thousand years.

Nom scientifique

Fregata magnificens

Autorité

Mathews, 1914

Ordre

Suliformes

Famille

Frégatidés

Genre

Fregata

Répartition et habitat

The magnificent frigatebird is widespread in the tropical Atlantic, breeding colonially in trees in Florida, the Caribbean and also along the Pacific coast of the Americas from Mexico to Ecuador, including the Galápagos Islands.<p>It has occurred as a vagrant as far from its normal range as the Isle of Man, Denmark, Spain, England, Nova Scotia, the Magdalen Islands, and British Columbia.

Aire de reproduction

AO, PO : e Pacific Ocean (w Mexico to Ecuador), Atlantic Ocean (e Mexico and Florida to Brazil), and Cape Verde Is. (where almost extinct)

Aire hors reproduction

to coastal n Baja California, Gulf of California and s to n Peru; to n Florida and Gulf of Mexico

Migration

Resident species

Comportement

This bird makes a shallow platform nest on top of both trees and bushes on islands and cays with mangroves. This nest is constructed out of branches and twigs.<p>The magnificent frigatebird lays a clutch of one clear white egg that measures .mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}68 by 47 millimetres (2+3⁄4 by 1+3⁄4 in) on average. This egg is incubated by both sexes for a period of 50 to 60 days. After the egg hatches, the male parent will abandon it, with the female staying to provision for the young for almost a year.<p>This species feeds mainly on fish, squid, jellyfish and crustaceans. Individual bird diets vary depending on food availability, preferred hunting technique, gender, and age.<p>It is a kleptoparasite, pecking at other seabirds to force them to disgorge their meals. After forcing the other seabird to regurgitate its meal, the magnificent frigatebird will dive and catch the prey before it hits the surface of the water.

Conservation

Tendance de la population

declining