Silvery Grebe

Is a medium-sized aquatic bird measuring between 26 and 28 centimeters in length, recognized by its slender profile and highly elegant silvery-grey plumage on its upperparts, which creates a sharp contrast with its pristine white underparts. It features a striking bright red to orange iris that stands out against its dark crown and hindneck. The species exhibits notable geographical variation divided into two main subspecies: the southern form (P. o. occipitalis), which possesses distinctive ash-grey ear-tufts and a dark throat, and the Andean form (P. o. juninensis), characterized by its golden-buff ear-tufts and completely white throat. Its bill is short, straight, and colored dark grey, highly adapted for catching active aquatic prey.

Geographical distribution: Is widely distributed along the Andes mountain range and the southern lowlands of South America. Its range spans from southwestern Colombia, through Ecuador, Peru, Bolivia, Chile, and Argentina, extending to the southernmost tip in Tierra del Fuego and the Falkland Islands. Southern populations undergo seasonal migrations toward northern regions during the austral winter, reaching southern Brazil, Paraguay, and Uruguay, whereas high-altitude Andean populations tend to be sedentary or perform minor altitudinal movements.

Habitat: Inhabits a diverse array of freshwater and brackish aquatic systems, ranging from lowland lakes and lagoons to high-altitude wetlands on the Andean Altiplano, reaching elevations of up to 5,000 meters above sea level. It prefers shallow bodies of water with abundant emergent and submerged macrophyte vegetation, although it can also utilize deep saline lakes and temporary pools during migratory stopovers outside of the breeding season.

Feeding: Is predominantly insectivorous, with a diet based on a wide variety of aquatic invertebrates, such as dipteran larvae, water beetles, chironomids, small crustaceans, and mollusks. It also opportunistically consumes small fish and aquatic plant material. The species captures its prey by performing agile, prolonged dives underwater, propelled by its lobed feet, searching both the water column and the substrate.

Behavior: Shows a highly gregarious nature, frequently forming dense flocks of dozens or even hundreds of individuals, especially during the non-breeding season. It is an exceptional swimmer and diver but is extremely clumsy on land due to the backward positioning of its legs. Its flight is strong and direct once airborne, but it requires a long running start over the water´s surface to take off. It exhibits a complex courtship display consisting of synchronized head movements and high-pitched, repetitive vocalizations.

Nesting: Breeds in colonial groups, establishing dense aggregations of nests that enhance defense against predators. It constructs floating platform nests made of decaying aquatic vegetation and algae, which are anchored to emergent reeds or cattails to prevent drifting. The female typically lays two to three bluish-white eggs that turn dark brown over time due to contact with damp nesting material. Both parents share the incubation duties for a period of 20 to 22 days and actively cooperate in protecting and carrying the precocial chicks on their backs.

Conservation status: Is currently evaluated as Least Concern (LC) on the IUCN Red List of Threatened Species. Although its overall population remains large and its geographical range is exceptionally broad, local populations face severe threats including the degradation of Andean wetlands, pollution from mining and agricultural runoff, and the introduction of invasive species like the American mink and predatory salmonid fish.