Seabirds form a diverse group within the class Aves, which includes species adapted to living, feeding, and breeding in marine environments. The term Aves comes from the Latin ‘avis‘, meaning ‘bird‘. Although these birds belong to different taxonomic orders, they share a series of physiological and behavioral adaptations that allow them to survive in often extreme oceanic environments. Seabirds are found in all the world’s oceans, from the Arctic to the Antarctic, and many undertake transoceanic migrations covering thousands of kilometers. Their habitats range from rocky coasts and beaches to the open sea, including cliffs, remote islands, and continental shelves where they find optimal conditions for nesting and feeding.
Species of seabirds display a wide variety of sizes and shapes, though they are generally well adapted to aquatic life. Their body length ranges from under 20 cm in small species such as Hydrobates pelagicus (European storm petrel), to more than 3 meters in wingspan in Diomedea exulans (wandering albatross), the bird with the largest wingspan in the world. Their wings are generally long and narrow, enabling them to glide over the ocean, while their legs are short and often webbed for swimming. Some species, such as auks and penguins, have developed wing-like flippers for efficient underwater propulsion. Their plumage is dense and water-resistant, and many have specialized uropygial glands to maintain waterproofing. Colors are usually subdued, with whites, grays, blacks, and browns predominating, providing camouflage in open environments.
Seabirds feed mainly on oceanic resources such as fish, crustaceans, squids, and plankton. Some species, such as loons and boobies, hunt by diving at high speed to capture prey, while others, such as procellariiforms, feed at the surface or dive shallowly. Laridae (gulls) and sternidae (terns) are often opportunistic, feeding on fish, scraps, and waste, and even stealing food from other birds. Certain species are specialized in following fish schools, fishing vessels, or upwelling areas where marine productivity is higher. Most seabirds regurgitate partially digested food to feed their chicks, which are usually raised in dense colonies in locations that are hard for terrestrial predators to reach.
There are about 350 species classified as seabirds, grouped into several main orders, including Procellariiformes (albatrosses, petrels, storm petrels), Sphenisciformes (penguins), Pelecaniformes (pelicans, cormorants, gannets), Charadriiformes (gulls, terns, auks), and Gaviiformes (loons). A notable curiosity is that many species can eliminate excess salt ingested from seawater through specialized glands located above the beak, enabling them to drink seawater safely. Several species are known for their long-distance migrations, such as Sterna paradisaea (Arctic tern), which makes the longest migration of any bird, traveling from the Arctic to the Antarctic each year. Despite their adaptability, many seabirds are threatened by pollution, overfishing, climate change, and the introduction of invasive species to their nesting sites.