The Peruvian booby (Sula variegata) is an endemic bird of the Peruvian current whose distribution is restricted to the west coast of South America from Punta Pariñas (4.6°S) in Peru to Concepción in Chile.[broken citation] It is the second most abundant seabird species that inhabits the Peruvian coast and the second most important guano-producing seabird. During the mid-twentieth century, the Peruvian booby population reached 3 million birds.[broken citation]
After ENSO 1982–83, less than 0.2 million birds were left. Peruvian booby population was recovering since 1984 and reached in 1996 more than 2.6 million birds. ENSO 1997–98 started after most boobies finished the breeding season and caused a southward migration of birds. The number of Peruvian boobies in Peru decreased through 1997 in about 87.1% due to this reason, few birds were found dead along the coast.
Peruvian boobies breed throughout the year. Main breeding season occurs during the austral spring-summer period (September to March) and most pairs may attempt to breed for a second time during the year depending on food availability. Peruvian boobies clutch size varies from one to four eggs, but clutches of two or three eggs, pale blue in color, are usually found. Eggs are incubated during approximately 4 to 5 weeks, both adults share the nest attendance. The rearing period lasts about 3 months. Breeding success depends on food availability and is related to colony location, colony size and timing of breeding.