The Peruvian Boobies, Sula variegata, are an endemic bird of the Peruvian coast whose distribution is restricted to the west coast of South America from Punta Pariñas (4.6°S) in Peru to Concepción in Chile (Harrison 1988). For more information, see our guide on backyard birds.
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 (Tovar et al. 1987).
Behaviour
The life of a Peruvian Booby involves more than just feeding. It also includes holding territory. They often fight fiercely with Brown Pelicans or Guanay Cormorants for nesting spaces. Territorial disputes can be quite intense. However, most of them end peacefully. These standoffs are almost always the result of a territory being actively defended.
When boobies are in a confrontation, they will often shake their heads before launching a jab. Cormorants usually respond by extending their necks, and at times, both species will engage in a “sky-pointing” display, where they extend their necks up as a visual message. These behaviours are ritualised to avoid serious injury and maintain dominance.
The Peruvian Boobies feed a lot during the day. Foraging trips are made up to three times a day, and usually last between one and five hours. They keep their trips close to home, which saves energy and ensures a quick return to the nest.
These birds use their entire body to forage. According to research, they spend 92% of their time foraging in flight, and very little time diving or sitting on water. The two main diving styles are V-shaped dives (fast plunges followed by rapid return to the surface) and U-shaped, where they stay at depth for a short time before rising.
The Peruvian Boobies forage between 4.5 and 68 km from their colonies. They cover a total distance of 14 to 171 km round-trip. Some birds use looped paths to feed at multiple sites. They feed at the furthest point away from their colony, before returning to it. This is a clever strategy that cuts down on travel time.
Description
The unique colouring of adult Peruvian Boobies makes them easy to recognise. The adult Peruvian Boobies have a white head, neck and upperparts. Their wings are covered in delicate white scales. The sharp grey legs and bill contrast with their wine-red eyes.
Juvenile Peruvian Boobies have a duller appearance. The plumage of the juvenile Peruvian Boobies is a more dusky grey, with a darker tone on their head and body. The breast feathers can have a white edge, while the face, legs and bill are a lighter shade of blue-grey. As they grow older, these shades will gradually darken.
It is interesting to note that females are usually larger than men. They weigh an average of 1.4 kilograms, 19% more than males. The wingspan of the females is slightly longer, reaching up to 150 centimetres. Their body length ranges between 71 and 76 cm. Although their egg size has been measured between 53 and 61 mm, the exact weight of an egg is not known. According to eBird, this species is well documented.
Habitat
Peruvian Boobies prefer the cool Humboldt Current waters, where the ideal temperature is between 13-22 °C. The main habitat of the Peruvian Boobies includes coastal islands like Isla Macabi and other rocky outcrops on the coasts in Peru and northern Chile. These areas offer the perfect conditions for nesting and foraging. According to Audubon Society, this species is well documented.
Nesting usually occurs on steep slopes or gentle hillsides, depending on the terrain. On narrow ledges, nesting can be done in small groups, such as 2-3 pairs. However, on flat ground, tens or thousands of birds may form massive colonies. The nesting site is critical, as it affects everything from chick density to chick survival.
Nests are made of a low circular rim, which is made up of pebbles or guano. The nests of these seabirds are usually placed eastward from their feeding areas, which is in line with their flight patterns. The competition for nesting sites is fierce. It often comes down to who can secure the site first and defend it the best.
Breeding / Nesting
Peruvian Boobies breed throughout the year. The 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, are usually found. Eggs are incubated for approximately 4 to 5 weeks, and 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.
Status
After ENSO 1982-83, fewer than 0.2 million birds were left. The 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 by about 87.1% due for this reason, few birds were found dead along the coast.
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