Snowy-crowned Tern

This medium-sized, elegant seabird exhibits an average body length of 33 to 35 centimeters. It is characterized by its exceptionally pale appearance, with a mantle and wings of a very soft, pearly gray and entirely white underparts. Unlike most other members of its genus, it lacks a solid black cap; instead, its head is white with a highly diagnostic, narrow black eye-stripe extending from the lores through the eye to the ear coverts. During the breeding season, its slender bill displays a bright orange-yellow color with a black subterminal band, while its legs and feet are a striking orange-red. In non-breeding plumage, the bill may appear mostly dark. The tail is deeply forked and white, allowing for highly agile aerial maneuvers.

Geographical distribution: It is native to the southern cone of South America, with breeding populations primarily concentrated in central and eastern Argentina (the Pampas and northern Patagonia), southern Brazil (specifically the state of Rio Grande do Sul), and throughout Uruguay. During the non-breeding season, populations disperse northward along the Atlantic coast, reaching as far as Rio de Janeiro. Additionally, some populations migrate westward across the Andes or around the continent to winter along the Pacific coast, from central Chile north to Peru.

Habitat: It primarily frequents inland freshwater and brackish environments, such as Pampas lagoons, marshes, swamps, and wetlands rich in emergent vegetation like rushes and reeds. It is also found in coastal estuaries, river mouths, salt marshes, and coastal lagoons. While it shows a distinct preference for interior lentic water bodies during the nesting season, it readily utilizes sandy beaches, rocky coastlines, and muddy tidal flats during its seasonal migrations and winter periods.

Feeding: Its diet consists mainly of small fish, supplemented by aquatic and terrestrial insects and small invertebrates. It captures prey using a specialized play-diving technique, hovering brief moments over the water before diving headfirst beneath the surface. It is also known to perform surface-dipping, snatching insects and small organisms directly from the water´s surface or catching insects mid-air during low, sweeping flights over wet meadows.

Behavior: This is a highly gregarious species that often gathers in mixed-species flocks with other terns for foraging and roosting. Its flight is light, buoyant, and exceptionally graceful, marked by constant, shallow wingbeats. Its vocalizations are sharp, grating, and repetitive, frequently uttered during territorial disputes or while foraging in groups. Seasonal movements are characterized by regional post-breeding dispersal and true migrations, which are highly dependent on local water levels and prey abundance.

Nesting: It breeds colonially, often establishing nesting sites alongside other waterbirds, such as gulls and other terns. The nests are constructed as floating platforms made of woven reeds, rushes, and other aquatic vegetation, or placed on muddy hummocks and small islands surrounded by deep water to deter terrestrial predators. A typical clutch consists of 2 to 3 eggs, which are brownish, olive, or greenish-buff in color, heavily blotched with dark brown spots. Both parents participate in incubating the eggs for approximately 21 to 24 days, and they cooperatively defend the nesting territory and provision the chicks.

Conservation status: It is currently classified as a species of Least Concern (LC) on the IUCN Red List. Although the global population is considered stable, localized threats persist, including the drainage of wetlands for agricultural expansion, chemical runoff and pollution in inland waterways, and direct human disturbance at nesting sites, which can lead to colony abandonment and reduced breeding success.