Justification of Red List Category
This species has an extremely 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.
Brooke (2004) estimated the global population to number around 150,000 individuals.
The population is suspected to be in decline owing to predation by invasive species.
The Herald Petrel is found predominately in the central and western Pacific, breeding on Raine Island (Australia), east to Easter Island (Chile). Two further colonies are found at Round Island (Mauritius) in the western Indian Ocean, and at the Trindade and Martim Vaz Islands, Brazil. Individuals have been recorded as far north as the Hawaiian Islands (U.S.A.) in the Pacific, and off the coast of northern Argentina in the Atlantic (del Hoyo et al. 1992).
This marine species is highly pelagic, rarely approaching land except at colonies. Very little is known about its diet, though squid have been recorded. Its breeding season is variable depending on location, with adults visiting colonies formed on oceanic islands, atolls or offershore stacks almost all year round. Colonies are loose, with nests being made in rocky crevices, on crags or on the ground up to 1000 m above sea level (del Hoyo et al. 1992).
The population on Henderson Island, which represents around 20% of the global population, experieces predation of chicks by rats; however, the majority of the population breeds on Ducie Island, from which rats were eradicated in 1997 (del Hoyo et al. 2018). The vast majority of the population breeds in the Pitcairns and, although not geographically bounded, it is thought their breeding habitat may be significantly affected due to changing sea levels, as well as damage to the coral reefs caused by an increase in sea temperature (del Hoyo et al. 2018).
Text account compilers
Fjagesund, T., Calvert, R., Harding, M., Butchart, S., Hermes, C., Ekstrom, J., Martin, R., Stuart, A.
BirdLife International (2020) Species factsheet: Pterodroma heraldica. Downloaded from http://www.birdlife.org on 23/10/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/10/2020.