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 fluctuating, 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 is extremely 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 estimated to number 1,200,000 individuals.
The population is suspected to be fluctuating owing to fluctuations in climatic conditions and, consequently, in the abundance of prey populations.
The Peruvian Booby is found in the area of the Humboldt Current, breeding from northern Peru to central Chile, with non-breeders being found as far as Ecuador and south-west Colombia.
This strictly marine species feeds close to the coast in cool upwelling waters, where food is abundant. It feeds almost exclusively on anchovetta, but will switch to other fish species when stocks collapse. Feeding mostly occurs by plunge-diving from moderate height, usually in groups of more than 30-40 individuals. Breeding is only loosely seasonal on bare, arid islets along rocky coasts, mostly on cliff ledges in Chile; in Peru, it prefers open, flat ground. It is largely sedentary, but will disperse widely during El Niño years (del Hoyo et al. 1992).
This species has been shown to be highly susceptible to the effects of El Niño events, due to their reliance on the Humboldt Current upwelling system for food (Ludynia et al. 2010). Previous El Niño events in the early 1980s devastated populations throughout Peru, and previous numbers of breeding pairs are yet to be reached (del Hoyo et al. 1992). This threat is unpredictable and has the capacity to cause massive declines. Guano mining also represents a disturbance to the Peruvian Booby. It is, however, less affected by overfishing than many other species in the region, as it does not require large anchovy schools (Tovar and Guillén 1987). As a result of lower stress placed on the species by other factors, the guano industry is not believed to have a significant effect on its population.
Text account compilers
Calvert, R., Ekstrom, J., Butchart, S., Fjagesund, T., Martin, R., Bennett, S.
BirdLife International (2022) Species factsheet: Sula variegata. Downloaded from http://www.birdlife.org on 14/08/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 14/08/2022.