Inca Tern

The Inca tern, Larosterna inca, is a bird of striking appearance, cloaked in a dark slate gray plumage with a paler throat and underwing coverts. A distinctive white mustache-like stripe extends from the base of its bill, fanning out into elegant, satiny feathers along the neck. The trailing edge of their wings and the edges of the outer primaries are touched with white. Their tails are black and moderately forked, adding to their graceful silhouette. Adults boast a brown iris, dark red legs and feet, and a dark red bill with a patch of bare yellow skin at its base. Juveniles initially display a purplish brown hue, transitioning through brownish gray as they mature, with their bill and legs evolving from a dark horn color to the red of adulthood.

Identification Tips

To identify the Inca tern, look for the unique white mustache and the overall dark gray body. The contrast of the white trailing edge on the wing and the red bill with yellow at the base are also key features. The moderately forked tail and the dark red legs and feet are additional characteristics to observe.

Habitat

The Inca tern is a coastal bird, favoring the rich marine environment of the Humboldt Current. It breeds on sea cliffs and guano islands, as well as utilizing man-made structures such as under piers and abandoned barges for nesting. It is also known to congregate with other seabirds on sandy beaches.

Distribution

This tern breeds from Lobos de Tierra in northern Peru to the Aconcagua River near Valparaíso, Chile. Post-breeding dispersal can lead some individuals north into Ecuador. It is a casual visitor to Panama and Costa Rica and has been recorded as a vagrant in Guatemala and Hawaii.

Behaviour

The Inca tern is largely sedentary, with some dispersion to the north after the breeding season. It has been known to wander great distances, as evidenced by sightings in Central America and Hawaii.

Song & Calls

At nesting colonies, the Inca tern is quite vocal, producing a variety of sounds including "raucous cackling notes" and "mewing" calls, the latter of which is reminiscent of a kitten's cry.

Breeding

Breeding for the Inca tern is not confined to a specific season, with evidence of breeding activities and eggs found at various times throughout the year. Nesting sites are diverse, ranging from rock fissures to abandoned burrows of other seabirds, and even on human structures. Clutches typically contain two eggs, with both parents sharing incubation duties and care for the young. Fledging occurs around four weeks post-hatching, with juveniles remaining dependent on their parents for an additional month.

Diet and Feeding

The Inca tern's diet consists mainly of small fish like anchoveta, supplemented by planktonic crustaceans and offal. They often form large flocks, sometimes numbering in the thousands, to attend fishing boats or to follow feeding marine mammals. They primarily catch prey through plunge-diving but will also pick food items from the surface while in flight or on the water.

Conservation status

The IUCN has classified the Inca tern as Near Threatened. The species faces threats from human fishing activities, climate change, and reduced reproductive success during El Niño events. Although the exact population size is unknown, it is believed to be in decline, with an estimate of around 150,000 individuals in 2011.