Common Tern

Characterized by an extremely elegant and streamlined silhouette, this medium-sized seabird measures between 31 and 35 centimeters in length with a wingspan ranging from 77 to 98 centimeters. During the nesting season, adults display a striking pale grey upper mantel that contrasts beautifully with pure white to very light grey underparts. Its head is crowned by a distinctive, glossy jet-black cap that extends down to the nape. The bill is strong, sharp, and primarily orange-red with a black tip, while the legs and feet are a vibrant bright red. Its deeply forked, swallow-like tail gives it outstanding aerial agility. In winter plumage, the forehead fades to white, the underparts become whiter, and the bill turns mostly blackish.

Geographical distribution: This species features a vast Holarctic distribution, nesting across temperate and subarctic regions of North America, Europe, and Asia. As a highly migratory bird, it undertakes spectacular long-distance journeys to spend the northern winter in tropical and subtropical waters of the Southern Hemisphere. Its wintering grounds span the coastlines of South America, sub-Saharan Africa, southern Asia, and Australasia. Along the Atlantic and Pacific coasts of South America, large flocks arrive annually, with key concentrations in nations like Brazil, Argentina, and Peru.

Habitat: Shows great ecological adaptability, occupying a diverse range of aquatic ecosystems. It is primarily found in coastal marine environments, including sandy beaches, barrier islands, estuaries, salt marshes, and sheltered bays. Uniquely among many of its relatives, it also establishes nesting colonies inland, utilizing large freshwater lakes, rivers with exposed gravel bars, and artificial reservoirs, provided there is open, vegetation-free terrain for roosting and nesting.

Feeding: It is predominantly piscivorous, relying on small, schooling fish that swim near the water´s surface. Important prey species include members of the Engraulidae (anchovies), Clupeidae (herring), and Ammodytidae (sand eels) families. This diet is periodically supplemented with marine crustaceans, soft-bodied mollusks, and flying insects captured mid-air. To secure its prey, it employs a specialized foraging technique involving hovering flight followed by a dramatic plunge-dive, submerging itself just below the surface to grab fish with its beak.

Behavior: Highly gregarious, this species aggregates in large flocks for foraging, roosting, migration, and nesting. It is renowned for its buoyant, graceful flight, capable of sudden, acrobatic aerial maneuvers. During the active nesting season, it becomes highly territorial and aggressively defensive, actively mobbing potential predators and human intruders by screaming harsh, buzzy vocalizations and executing rapid dive-bombs. Migration occurs in synchronized, dense waves along coastlines and oceanic flyways.

Nesting: Nesting takes place in dense, noisy colonies on islands, beaches, or dunes. The nest is a simple scrape in the sand, pebbles, or shell-debris, occasionally lined with dry grass or seaweed. The female typically lays 2 to 3 cryptically colored eggs, which are olive-grey or buff with dark brown speckles to blend into the substrate. Both parents share incubation duties for 21 to 25 days and cooperate closely in rearing the semi-precocial chicks, feeding them small whole fish until they fledge.

Conservation status: Globally, the International Union for Conservation of Nature (IUCN) lists Sterna hirundo as Least Concern (LC) due to its large global population size and extensive range. However, local populations are often subject to intense management and conservation efforts. Major localized threats include the loss and degradation of sandy coastal habitats due to real estate development and tourism, human disturbance during the nesting cycle, pollution from plastics and heavy metals, and predation by introduced mammals such as domestic cats, rats, and feral dogs, which can decimate colonial nesting success.