The Inca tern is one of the world’s most beautiful and interesting birds. It occurs along the Pacific Coast from northern Peru to central Chile. This bird is easily recognizable with its dark gray body, and red-orange beak and claws, and its lovely white moustache. It is an adept flier that swoops and hovers before it dives after its prey. It sometimes plucks pieces of fish out from between sea lions’ teeth. Unfortunately, their populations are declining quickly because of the loss of nesting sites. They have been included in the “close to vanishing species” category. Inca terns in the wild live up to 14 years and in captivity up to 20 years.
The Inca tern inhabits South America’s west coast, from Ecuador to Peru and Chile. It is endemic to the area of the Humboldt Current. It breeds on coasts with sandy beaches and rocky cliffs, and may also frequent inshore guano islands and offshore islands near rocky coasts.
Habits and lifestyle
The Inca tern is a diurnal, gregarious species, living and nesting in large colonies numbering several thousand birds, often close to gull colonies. Inca terns follow fishing boats and often associate with whales and sea lions when feeding, stealing food from these fellow marine mammals. Inca terns feed by plunge-diving from a height, after a brief flight above their prey, or by surface-dipping, whereby they swim or sit on the water and pick up prey from the surface. They are not strong swimmers, as their webbed feet are not big enough. Inca terns remain resident within their range, though non-breeding birds sometimes move, depending on food resources.
ternery or "U" of terns, straightness
Diet and nutrition
Inca terns are carnivores (piscivores), they mainly eat the small anchovetta in the south-eastern Pacific Ocean, and they also eat crustaceans and offal.
Inca terns are monogamous, pairs often returning to the same nesting site year on year. Courtship consists of an elaborate ritual, particularly for birds seeking their mate for the very first time. Males perform an agile flight display to impress their chosen female. They also perform courtship feeding while following the female while flying, with a fish in their bill. This species breeds twice a year, firstly between April and July, secondly between October and December. Nests are on guano islands or sandy beaches and they choose deep rock crevices where there are many cavities and cliffs that offer good protection. Chicks hatching in deep holes are given protection for longer from predators, whereas nests that are further from cliffs are more accessible to raptors and large seabirds. 1-3 eggs are laid and incubation lasts for about 3-4 weeks. The parents both incubate and feed the chicks. The young are grayish in color and fledge at about 4 weeks old. They reach their independence one month later and will be ready to breed at age 2 or 3.
Inca tern numbers are affected by food resources, as well as El Niño and other strong storms. Populations decline during such severe storms, though they fairly quickly become stable again. The biggest threat currently is over-fishing, as this reduces the fish available for the terns to eat. Production of guano can also reduce the number of nesting sites available, and cats and rats may eat eggs and chicks.
According to the IUCN Red List, the total Inca tern population size is more than 150,000 individuals. Currently this species is classified as Near Threatened (NT) and their numbers today are decreasing.
Fun facts for kids
- The red beak, red legs and characteristic white moustache of an Inca tern do not develop until they reach 1-2 years old.
- The moustache length of the Inca tern seems related to its health. The longest moustaches belong to the healthiest birds.
- The adult Inca terns with the longer moustaches are the most productive birds and they have heavier chicks with better immune responses.
- Inca terns feed in a different depth of water to Humboldt penguins and thus the two are able to coexist. The terns will also nest in abandoned Humboldt penguin nests.
- Inca terns make cat-like mewing sounds.
- When sea lions catch fish and then haul out onto rocks in order to eat them, large flocks of Inca terns may hover above them and then plunge down and steal the chewed-up food out from between the teeth of the sea lions.