Lesser Frigatebird Fregata ariel


Justification of Red List Category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
Del Hoyo et al. (1992) estimate that the population is likely several hundred thousand individuals. Therefore, the population is tentatively placed here in the range 100,000-499,999 individuals.

Trend justification
The population is suspected to be in decline owing to ongoing habitat destruction and unsustainable levels of exploitation.

Distribution and population

Major breeding populations of the Lesser Frigatebird are found in tropical waters of the Indian and Pacific Ocean (excluding the east Pacific), as well as one population in the South Atlantic (Trinidade and Martim Vaz, Brazil). Outside the breeding season it is sedentary, with immature and non-breeding individuals dispering throughout tropical seas, especially of the Indian and Pacific Oceans (del Hoyo et al. 1992).


The Lesser Frigatebird breeds on small, remote tropical and sub-tropical islands, in mangroves or bushes, and even on bare ground. It feeds mainly on fish (especially flying-fish) and squid, but also on seabird eggs and chicks, carrion and fish scraps (del Hoyo et al. 1992). Kleptoparasitic behaviour is observed in this species; however it is unlikely to be a major chick-provisioning resource (Congdon and Preker 2004).


Climatic events associated with ENSO (El Niño Southern Oscillation) can cause synchronised breeding failure, as observed in the central Pacific (Orta et al. 2018). Human disturbance has minor effects on the species; skiffs approaching the beach to land their crew triggers flushing of nesting and roosting Frigatebirds (Borsa and Boiteux 2007 in Borsa et al. 2010).

The Atlantic race F. ariel trinitatis is arguably deserving of species status and is confined to a very small population on the island of Trindade (Olson 2017). House mice Mus musculus remain on the main island of Trindade where they are likely to prevent the recolonisation of the greatly depleted Atlantic subspecies (Orta et al. 2018).


Text account compilers
Fjagesund, T., Calvert, R., Butchart, S., Martin, R., Miller, E., Ekstrom, J.

Recommended citation
BirdLife International (2023) Species factsheet: Fregata ariel. Downloaded from on 31/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from on 31/03/2023.