Coscoroba Swan

This is a large waterfowl species that exhibits intermediate morphological characteristics between a swan and a goose, characterized by a nearly entirely pure white plumage, with the exception of the tips of the primary wing feathers which are glossy black, a feature that is typically visible only when the bird is in flight. Its most defining physical trait is a robust, duck-like, flattened bill of a vibrant coral-red or bright pink hue, lacking any frontal knob, paired with long, sturdy, deep pink legs and feet that provide it with a more upright stance than other swans. The total body length ranges from 90 to 115 centimeters (35 to 45 inches), with a weight varying between 3.2 and 5.4 kilograms (7 to 12 pounds), showing minor sexual dimorphism as males are slightly larger and heavier than females. Juveniles display a mottled pattern of grayish and brownish patches over a dirty-white base, with their bills and legs exhibiting a dull gray color that transitions to the adult pinkish-red over their first year.

Geographical distribution: It is native to the Southern Cone of South America, with its primary breeding grounds located in southern Chile (ranging from the Los Lagos Region down to Magallanes) and southern Argentina (throughout Patagonia), as well as on the Falkland Islands. During the austral winter, southern populations undertake medium-distance migrations northward to warmer temperate climates, spreading into central Chile, northern Argentina, Uruguay, Paraguay, and southern Brazil (especially within the state of Rio Grande do Sul).

Habitat: It primarily frequents shallow, calm bodies of water, showing a strong preference for freshwater or brackish lagoons, marshes, swamps, estuaries, and shallow coastal wetlands with a dense cover of emergent and floating vegetation. It displays a high tolerance for varying salinity levels, which allows it to successfully inhabit both inland saline lakes in the Patagonian steppes and sheltered maritime bays, while generally avoiding fast-flowing rivers or deep, open waters that lack adequate shoreline cover.

Feeding: It has an omnivorous diet with a strong emphasis on herbivory, primarily consuming aquatic macrophytes, algae, seeds, tender grasses, and roots extracted from the muddy substrate. Its specialized bill is equipped with internal lamellae that allow it to filter water and mud, trapping small aquatic invertebrates such as mollusks, small crustaceans, insect larvae, and occasionally small fish, utilizing surface-dabbling, head-dipping, and upending techniques.

Behavior: It is a highly gregarious species outside the breeding season, frequently gathering in large, noisy flocks of hundreds of individuals to feed and roost together. It is exceptionally vocal, known for emitting a loud, trumpet-like, three-syllable call transliterated as "cos-co-ro-ba", which serves to maintain flock cohesion and advertise territory. While typically wary and quick to take flight in the presence of humans, it becomes highly aggressive toward intruders and other waterfowl when establishing and defending its nesting territory.

Nesting: It establishes long-term, monogamous pair bonds, beginning its reproductive cycle in late winter. The pair constructs a large, mound-like nest composed of reeds, rushes, and aquatic grasses, built on small islands, within dense reedbeds, or on floating vegetation mats to safeguard it from terrestrial predators. The female deposits a clutch of 4 to 7 creamy-white eggs, which she incubates solely for a period of approximately 35 days, while the male remains nearby to aggressively defend the territory. The chicks are precocial and leave the nest shortly after hatching, being closely guarded and guided by both parents until they fledge and gain independence.

Conservation status: It is currently classified as Least Concern (LC) on the IUCN Red List of Threatened Species. Although its overall population is considered stable across its extensive range, localized populations face threats from habitat loss and wetland degradation caused by agricultural expansion, water pollution, coastal development projects, and sporadic illegal hunting.