Peruvian Booby Sula variegata Scientific name definitions

The Peruvian Booby is a brown-and-white Sulid of the Humboldt Current off western South America. Like the Blue-footed Booby (Sula nebouxii), the Peruvian has brown upperparts, a gray bill, and white head and underparts. Peruvian, however, has gray rather than blue legs, a whiter head, more white mottling on the upperwings, and no white patch at the center of the lower back. This species breeds from northern Peru to central Chile on small coastal islands on cliff ledges or bare ground. While generally rather sedentary, El Niño events may trigger massive dispersal and vagrancy north to Colombia and south to southern Chile. During these events, the upwelling patterns of coastal Peru and Chile are altered, and the food sources that the Peruvian Booby and other seabirds depend on are effectively cut off. Typically, however, this species feeds in groups, often with other seabirds, by plunge-diving in pursuit of schooling fish.

71–76 cm; two males 1250 g and 1350 g, two females 1500 g and 1540 g. Head and neck white, rest of upperparts including upperwing  umber brown, each feather with whitish margin at tip giving it a scaly pattern, primaries and its coverts entirely dark, the longer uppertail-coverts are largely pale; tail with whitish shafts, mostly umber brown with small paler tips, central rectrices often extensively paler at base as well as at tip; underwing has dusky brownish remiges and greater coverts, rest of of wing coverts slightly darker umber brown with diffuse paler tips except for partly paler median and some anterior lesser coverts forming two light bars along central wing, sometimes all the underwing look mostly dusky brownish but for the white axillaries; underparts white except for blurred umber brown and whitish spotting on thigh and rear flanks; iris deep chestnut to brownish red; bill  darkish grey to dull horn colour; facial skin around eye, on lores and on chin and upper throat slate to grey-black; legs  plumbeous grey to bluish grey, rarely sky blue. Sexes similar, females average slightly larger. Immature much as adult but the head and neck sullied brownish or with scattered brownish markings, upperpart feathers darker and with smaller pale tips, tail more extensively blackish, pale areas of underparts with dense blurred dull brownish spotting, at first the iris is grey and the legs are pale dull fleshy. Most similar to S. nebouxii, but the upperwing looks spotted or scaled, dorsum more regularly patterned, underwing pattern ill-defined, less clean, more spotted; adults readily told by darker iris and entirely white head and neck; young with paler head and neck and brownish abdomen, not contrasting with chest; confusion with other species unlikely.

• Blue-footed x Peruvian Booby (hybrid) Sula nebouxii x variegata

W coast of S America in area of Humboldt Current; breeding grounds from N Peru (Piura) (3 Schulenberg, T. S., D. F. Stotz, D. F. Lane, J. P. O’Neill, and T. A. Parker (2007). Birds of Peru. Princeton University Press, Princeton, NJ, USA. Close ) to C Chile (Mocha I), non-breeders dispersing as far as SW Ecuador, rarely SW Colombia.

Strictly marine. Feeds close to the coast in cool, rich waters of upwelling, where food extraordinarily abundant. Nests on bare, arid islets along rocky coast, mostly on cliff ledges in Chile , but in Peru prefers open, flat ground, with significantly lower temperatures than at nest sites of S. nebouxii.

Largely sedentary, but occurrence of El Niño causes mass desertion of area and large-scale vagrancy N to Colombia or farther S in Chile. Small numbers occur in all months of year off S Ecuador, though not breeding there. Chilean population bolstered by influx of migrants during Mar–Oct.

Used to feed almost exclusively on abundant supplies of anchoveta (Engraulis ringens), but, after collapse of stocks, may have switched partially to sardina (Sardinops sagax); also takes some mackerel (Scomber japonicus) and other fish. Feeds by plunge-diving  , usually from moderate height and almost invariably in groups, often of 30–40 or more individuals. Study of foraging and diving behaviour, and at-sea distribution and food selection, of individuals breeding at Pajaros I, off N Chile, revealed that the boobies foraged in vicinity of breeding colony, making short foraging trips (duration varying from a few minutes to several hours) to average range of 17·1 km, with diving recorded at sites between 2 m and 10 km from coast and to maximum depth of 10 m (average depth 4.3 m); their diet was highly variable from one year to another, but Chilean jack mackerel (Trachurus murphyi) and anchoveta were overall dominant prey (4 Ludynia, K., Garthe, S. and Luna-Jorquera, G. (2010). Distribution and foraging behaviour of the Peruvian Booby (Sula variegata) off northern Chile. Journal of Ornithology. 151: 103-111. DOI 10.1007/s10336-009-0431-1. Close ).

At colony, male utters high-pitched chittering calls and female makes various grunting and low bickering sounds. Similar calls emitted during fishing bouts.

Only loosely seasonal, mostly Sept–Feb in Peru; in Chile laying occurs Jan/Feb. Nests on ground in enormous colonies; nest  generally a loose pile of seaweed, held together by droppings, but sometimes no nest at all. Clutch 1–4 eggs, average 3; incubation period c. 42 days; chicks  have whitish down  ; fledging period c. 78–105 days; post-fledging care c. 62 days. Age of first breeding probably 2–3 years.

Not globally threatened (Least Concern). Numerous, and locally abundant. Global population very large; some annual fluctuation in numbers. Population was greatly reduced during exploitation of guano, and through disturbance and egg-collecting; main problem subsequently commercial overfishing, causing 1972 crash of anchoveta stocks, although this species seems to be proportionately less affected by overfishing than do other "guano birds". Always susceptible to devastation by El Niño events, and total population slumped from 2,690,000 breeding birds in 1981–1982 to only 730,000 during El Niño of 1982–1983; partial recovery to 1,160,000 individuals by 1985–1986. Legally protected throughout range, but colonies still exploited for guano.