Ascension : Conservation Weekly
Submitted by The Islander (Conservation Office) 05.08.2010 (Article Archived on 19.08.2010)

The Ascension Frigate bird is unique, breeding only on Ascension Island. It once occurred in huge numbers on the main island

Ascension Island Conservation Department

The Ascension Frigate Bird

The Ascension Frigate bird is unique, breeding only on Ascension Island. It once occurred in huge numbers on the main island but rapidly declined because of hunting by sailors and colonists and predation by introduced rats and cats. Today the species nests only on the summit of isolated Boatswain Bird Island.

This endemic seabird was evidently abundant on the mainland of Ascension in the past but now breeds only on Boatswain Bird Island, with a population of less than 10,000 birds. They can be seen at Long beach feeding. They feed mainly on fish, which they pick from the sea surface. All prey is taken in flight, as frigate birds cannot take off from water. Frigate birds also pursue other seabird species and force them to drop their catch. They take turtle hatchlings and at Mars Bay and Waterside they raid sooty tern colonies for unguarded chicks.  

                                                                       Adult female frigate bird with chicks on BBI   

Nesting

The Ascension Frigate breeds through out the year but nesting activity peaks around October-November time. During courtship males inflate their throat sacs and vibrate their wings to attract females flying ahead. The Male Frigate is black with a red throat pouch and the females are black, but have a dark brown collar and breast band. Juveniles have white heads. The nest is a simple platform of vegetable matter and other debris usually among rocks on flat areas or broad cliff ledges. The single white egg is unusually small for the size of the bird, its 44 day incubation being shared by both parents. The chick, although fledged when six months old, is dependent on its parents for most of its first year. This means that frigate birds can only nest in alternate years.

                                                                          Adult male frigate bird displaying on BBI

Volunteers welcome. Please contact Olivia Renshaw or Natasha Williams. Ascension Island Conservation Department. Georgetown. Tel: 6359. Email:  olivia.renshaw@ascension.gov.ac

natasha.williams@ascension.gov.ac