Australian Biological Resources Study

Australian Faunal Directory

Family FREGATIDAE Degland & Gerbe, 1867

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Family FREGATIDAE Degland & Gerbe, 1867

 

Introduction

The pelagic seabird family Fregatidae (frigatebirds) has been recognised by several authorities (Dorst & Mougin 1979; Kennedy & Spencer 2003; Christidis & Boles 2008). Fregatids are centred in tropical and subtropical oceans, frequenting oceanic islands and adjacent seas. All are gregarious, non migratory or local wanderers. Contrary to this, immatures do wander far from their nesting sites. Characteristics of the family are their semipalmate webbing, linking all four totiplamate toes, the breastbone has the furcula totally fused, and males have an expandable red gular pouch. They are unable to swim despite the webbed feet and also due to their inability to produce sufficient oil from their preen glands.

There are 14 subspecies based on five species in a single genus, three of which occur in Australian or Australian territorial waters. They are readily identified by the extreme length of their narrow, pointed and angular wings (wingspan up to 2.3 m) and long, deeply forked tails. All have brownish black, slightly iridescent plumage which is interrupted by white or rufous on the underside of females and young birds; the females are larger than the males. Fregatids have long, slightly decurved bills that generally are bone coloured. During the breeding season the males inflate their large, bare and expandable gular sac, using it to assist in their courtship behaviour. Displays using this sac are made from exposed tree limbs or during flight over the proposed nesting area.

The tarsi are feathered and short to the extreme and the four toes are semitotipalmate with the middle claw pectinate. Placement of the feet well back on their body makes for an ungainly appearance on the ground and they tend to restrict this activity to the nest area; they require raised obstacles from which to take flight. On the wing they are magnificent and agile fliers, their extremely long slim wings enabling remarkable aerial skills. These abilities are aided by their low body mass. In accordance with their pelagic existence vocalisation is restricted to courtship and activities about the nest; at sea they restrict themselves to occasional harsh croaks, whistling or bill rattling. Males may also produce a resonating hooting or drumming during courtship.

As a piscivorous group, their foods include a variety of foods such as flying fish, squid, crustacean, jellyfish or turtles, all procured from the ocean surface while by swooping or hovering in their pelagic habitat. Some food is obtained through their acknowledged parasitical prowess for robber tactics; they take prey collected by other species or remove chicks of other species from their nests.

Away from the nesting grounds, frigatebirds are seen singly or in pairs, although at large food congregations they gather in gregarious groups. Characteristically, frigatebirds are monogamous apart from breeding pairs nesting in colonies. On a remote island, the male constructs a frail, untidy stick nest. Twigs are gathered by the female, and the male places them either on the ground or at the top of mangroves or other low trees. Each nesting pair produces a single white and chalky ovoid egg, rarely two, which is incubated by both adults. After 44–55 days incubation, the ensuing young is cared for by both adults. This nidicolous nestling is rapidly covered by pure white down.

 

History of changes

Note that this list may be incomplete for dates prior to September 2013.
Published As part of group Action Date Action Type Compiler(s)
10-Nov-2020 PELECANIFORMES 26-Aug-2014 MODIFIED Dr Wayne Longmore
12-Feb-2010 (import)