Frigatebirds

A most peculiar group of large parasitic seabirds of the tropical seas. Closely related to the cormorants and in their own way unequalled in their flying capacities. Their long bills are perfectly adapted to their function. With latericorns forming a notch at the distal end and strongly hooked upper and lower ungues it provides the so called Man o’ war bird with a superb tool to grab the prey of their fellow seabirds in full flight.
The five species differ mainly in size. All of them are more ore less similar in shape and coloration, but there is very much variation in plumage colors depending on age and sex. Bill colors can also vary very much, from bluish grey, pinkish to almost black. Identification can be very difficult at sea.
Ranges of all species overlap to a certain extent to that of another frigatebird, so confusion is a serious risk even when found dead.

Genus Fregata

Five species:

  • Ascension Frigatebird Fregata aquila. Tropical Atlantic, Boswain I., Ascension I.
  • Christmas or Andrew’s Frigatebird Fregata andrewsi. Christmas I. north-east Indian Ocean.
  • Magnificent Frigatebird Fregata magnificens. Atlantic and Pacific coasts of the Americas.
  • Great Frigatebird Fregata minor. Indo-Pacific distribution with two outposts in the Atlantic. Four subspecies:
    • F. m. minor. Indian Ocean, breeding Cocos and Christmas I., Paracel Is. and Gunung Api.
    • F. m. palmerstoni. Western and central Pacific, dispersing through Polynesia.
    • F. m. ridgwayi. Eastern Pacific Ocean.
    • F. m. nicolli, Atlantic Ocean
    • F. m. aldabrensis. Western Indian Ocean.
  • Lesser Frigatebird Fregata ariel. Pacific and Indian Ocean with two outposts in the Atlantic. Three subspecies:
    • F. a. ariel, breeding central and eastern Indian Ocean, dispersing widely.
    • F. a. trinidatis, Atlantic Ocean.
    • F. a. iredalei, western Indian Ocean.


Ascension Frigatebird Fregata aquila. Ascension Island
Total: 148.5 mm, unsexed adult. Courtesey of Steve Holliday

skull Magnificent Frigatebird Fregata magnificens
Magnificent Frigatebird Fregata magnificens. Location unknown.
Culmen: 115.3 mm; total: 173 mm, unsexed adult
skull Great Frigatebird Fregata minor
Great Frigatebird Fregata minor, Tern island, Hawaii
Culmen: 120.8; Total: 181.5, unsexed adult (left lachrimal missing)

Osteology

  • Skull
  • Flight apparatus
  • Pelvis and Legs
  • Vertebrae

References