Justification of Red List Category
Although this species may have a restricted range, it is not believed to 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.
The population is suspected to be in decline owing to climate change and human disturbance.
Major breeding populations of the Great Frigatebird are found in tropical waters of the Pacific and Indian Ocean, as well as one population in the South Atlantic (Trinidade and Martim Vaz, Brazil). It is predominately sedentary, with immature and non-breeding individuals dispersing throughout the tropical seas with the exception of the east and central Atlantic.
The Great Frigatebird breeds on small, remote tropical and sub-tropical islands, in mangroves or bushes and occasionally on bare ground (del Hoyo et al. 1992). Fish, squid and chicks of other bird species (e.g. Sooty Terns) have all been identified as prey (Weimerskirch et al. 2004). It is frequently observed attempting to steal food from other bird species (Vickery and Brooke 1994). However, this behaviour represents a minor source of energy intake (Vickery and Brooke 1994, Weimerskirch et al. 2004), and individuals are frequently observed foraging at the coast or inland at most breeding sites (Weimerskirch et al. 2004).
Suspected increases in the frequency of ENSO (El Niño Southern Oscillation) events with future global warming (Timmermann et al. 1999) may pose a threat to the survival and breeding success of Great Frigatebirds of unknown severity (Anderson 1989, Weimerskirch et al. 2010). Human disturbance has minor effects on the species; skiffs approaching the beach to land their crew triggers flushing of nesting and roosting individuals (Borsa and Boiteux 2007 in Borsa et al. 2010).
Text account compilers
Ekstrom, J., Calvert, R., Fjagesund, T., Martin, R., Butchart, S., Miller, E.
BirdLife International (2019) Species factsheet: Fregata minor. Downloaded from http://www.birdlife.org on 24/10/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/10/2019.