Guanay Cormorant

This is a large, striking seabird measuring approximately 28 to 30 inches (71 to 76 cm) in length, recognized by its contrasting plumage. The dorsal region, thighs, and head are covered in sleek, dark feathers displaying a metallic greenish-bronze sheen, while the throat, breast, and belly are a contrasting, pristine pure white. Its most remarkable diagnostic feature is the patch of bare, bright scarlet-red skin surrounding the eyes, which contrasts beautifully with its slate-grey bill and pale pink feet. During the breeding season, adults may develop small white tufts behind the eyes and ornamental white filoplumes along the sides of the neck.

Geographical distribution: Mainly distributed along the hyper-productive Pacific coast of South America, this species is deeply associated with the cold waters of the Humboldt Current. The primary breeding range extends from northern Peru down to central Chile. Outside the breeding cycle, the species exhibits erratic wandering behaviors, with individuals migrating northward toward the shores of Ecuador, while some southern populations occasionally cross over to the Atlantic coasts of Argentina, tracking the movement of pelagic fish stocks.

Habitat: Strictly marine and coastal, it thrives in regions characterized by major ecological upwellings where deep, nutrient-filled waters sustain immense marine life. It utilizes flat or gently sloping surfaces on coastal guano islands, barren headlands, and steep rocky cliffs as roosting and nesting grounds. It prefers shallow inshore waters, protected bays, and harbors, rarely venturing far into open ocean waters beyond the limits of the continental shelf.

Feeding: The diet is highly specialized and relies almost entirely on small, schooling pelagic fishes. The Peruvian anchoveta (Engraulis ringens) constitutes the absolute bulk of its nourishment, supplemented occasionally by the South American pilchard (Sardinops sagax) and other small fishes. To capture its prey, it performs pursuit-diving maneuvers propelled by its powerful webbed feet, plunging to depths typically between 30 to 100 feet (10 to 30 meters) to actively chase fish within the water column.

Behavior: Highly social and gregarious, it forms some of the largest and most dense avian aggregations in the world. They fly in coordinated, low-altitude V-formations or long, undulating lines just above the water surface. When foraging, thousands of individuals gather on the water surface in dense configurations known as rafts, working together to herd schools of fish upward. Environmental anomalies like the El Niño-Southern Oscillation (ENSO) drastically alter their behavior, forcing massive southward migrations or widespread dispersal in search of food.

Nesting: Nesting takes place in massive, highly packed colonies established on flat or moderately sloped plateaus of offshore islands. Nest density is remarkably high, sometimes reaching up to three nests per square meter, creating a continuous blanket of breeding birds. The nest is a crater-topped mound built primarily from accumulated guano, feathers, sand, and coastal debris, cemented together to form a solid structure. The clutch typically consists of two to three bluish-white eggs that are incubated by both parents for approximately thirty days.

Conservation status: Currently evaluated as Near Threatened (NT) on the IUCN Red List. Historically numbering in the tens of millions, populations have suffered massive crashes due to overfishing of their primary food sources and intense El Niño events. Modern threats to their survival include competition with commercial purse-seine fisheries, human disturbance during guano harvesting, marine pollution, and habitat degradation caused by climate change.