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 at least 500,000 individuals.
The population is suspected to be in decline owing to predation.
This species can be found off the coast of North America and South America, from Baja California (Mexico) in the north to central Chile in the south. It breeds on the Galapagos Islands, Ecuador, and on Pescadores and San Gallan Islands, Peru.
This marine species can be found over pelagic waters usually well offshore except when near colonies. It feeds mostly on small fish, squid and crustaceans caught on the wing by pattering and dipping, or by surface-seizing while sitting on the water. It feeds mainly at night. During breeding it forms colonies on cliffs or lava fields, nesting in rock crevices or under vegetation cover (del Hoyo et al. 1992).
Birds are eaten in large numbers by Short-eared Owls Asio flammeus galapagoensis (Harris 1969); however, this is unlikely to be above natural levels of mortality. As the primary source of nesting failure is intraspecific competition (Harris 1969), low-level loss of adults is unlikely to have a lasting effect on the population.
Text account compilers
Ekstrom, J., Calvert, R., Butchart, S., Fjagesund, T., Hermes, C., Martin, R., Miller, E., Stuart, A.
BirdLife International (2021) Species factsheet: Hydrobates tethys. Downloaded from http://www.birdlife.org on 19/01/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/01/2021.