Fregatidae Frigatebirds
Version: 1.0 — Published March 4, 2020
Introduction
Fregatidae has two colloquial English names, frigatebirds and man-o’-war birds, both of which conjure up swift and lethal sea craft, and frigatebirds vie with jaegers as the consummate pirates of the sea. They frequently steal food from other birds, targeting those returning, laden, to their breeding colonies. With many bones fused in the thoracic girdle, the skeleton has the lightest wing-loading of any bird, weighing only half the weight of the feathers. Frigatebirds somehow manage to have both long narrow wings for efficient soaring and remarkable maneuverability. They readily pluck flying fish from the air and other fish from the very surface, but lacking waterproof plumage they are loath to dive or swim and will drown if their feathers get too saturated.
Habitat
During the non-breeding season, frigatebirds stay at sea, remaining on the wing for many days at a time. Frigatebirds nest on offshore islands, and during the breeding season their foraging range is considerably constrained.
Diet and Foraging
Frigatebirds feed on a variety of marine vertebrates and invertebrates, with a particular preference for flying fish and squid. They will take an assortment of other items, including many other types of fish, jellyfish, and, during the breeding season, even the eggs and chicks of other seabirds. Although frigatebirds are sometimes kleptoparasites, pirating food from other birds, they more frequently catch food on their own, snatching prey near the surface of the water.
Breeding
Frigatebirds are monogamous with biparental care. Males court from an old nest from the previous year, inflating the scarlet gular pouch and vibrating their spread wings and head energetically whenever a female flies overhead. Pairs then collaborate in nest construction, with the males gathering most of the sticks for the female to mold into a nest. Most frigatebirds build a simple platform nest in a small bush or tree, but the Ascension Frigatebird Fre gata aquila nests on the ground and builds no nest. Female frigatebirds lay a single egg, and both parents help with incubation, brooding, and bringing food to the chick. Incubation takes 40 to 55 days, and, depending on food availability, the chicks fledge after 135 to 210 days. Fledglings remain in contact with their parents for some time, occasionally being fed by them up to 14 months after fledging.
Conservation Status
Two species (40%) face some level of conservation concern (1 VU, 1 CR). The Christmas Frigatebird Fregata andrewsi, currently listed as critically endangered, is restricted to Christmas Island in the Indian Ocean, and its rapid decline is due to deforestation.
Systematics History
The frigatebirds belong in Suliformes, where they are sister to the remaining three families in this order: Phalacrocoracidae, Anhingidae, and Sulidae (Livezey & Zusi 2001, Ericson et al. 2006a, Hackett et al. 2008). The hypothesis (Livezey & Zusi 2007) that Fregatidae is also allied with Phaethontidae has not been supported by molecular studies (Hackett et al. 2008).
Conservation Status
Least Concern |
60%
|
---|---|
Near Threatened |
0%
|
Vulnerable |
40%
|
Endangered |
0%
|
Critically Endangered |
0%
|
Extinct in the Wild |
0%
|
Extinct |
0%
|
Not Evaluated |
0%
|
Data Deficient |
0%
|
Unknown |
0%
|
Data provided by IUCN (2023) Red List. More information