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). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to 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 global population is estimated to number > c.32,000 individuals (del Hoyo et al. 1992), while the population of Japan has been estimated at < c.100 breeding pairs and < c.50 individuals on migration (Brazil 2009).
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.
The Red-tailed Tropicbird nests in the southern Indian Ocean, and just north of the Tropic of Cancer and south of the Tropic of Capricorn in the Pacific Ocean. It breeds on islands, but can also be found on the south-west coast of Australia.
This species feeds mostly on fish, especially flying-fish, large quantities of squid and occasionally crustaceans. Prey is caught by plunge-diving, but flying-fish can be taken in flight. Breeding occurs seasonally in loose colonies on small, remote oceanic islands mostly on inaccessible cliffs. No regular migrations are known; adults can be found in the vicinity of colonies all year round (del Hoyo et al. 1992).
Rats have caused significant losses in Red-tailed Tropicbird colonies in the past and they remain vulnerable to further introductions throughout the range. It does, however, occur on many currently predator-free islands and has been shown to benefit from eradications that have been carried out to date (VanderWerf et al. 2014).
Text account compilers
Fjagesund, T., Calvert, R., Butchart, S., Hermes, C., Ekstrom, J., Martin, R., Stuart, A.
BirdLife International (2019) Species factsheet: Phaethon rubricauda. Downloaded from http://www.birdlife.org on 21/04/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/04/2019.