The Southern Lapwing (Vanellus chilensis) is a wader in the order Charadriiformes. It is a common and widespread resident throughout South America, except in densely forested regions, the higher parts of the Andes and the arid coast of part of western South America. This bird is particularly common in the basin of the Rio de la Plata.

It is 32 to 38 cm (13 to 15 in) in length and weighs approximately 250 to 425 g (8.8 to 15.0 oz).

This is a lapwing of lake and river banks or open grassland. It has benefited from the extension of the latter habitat through widespread cattle ranching. It is well adapted to human disturbance and is increasing its range in response to deforestation and cultivation.

It breeds on grassland and sometimes ploughed fields, and has an aerobatic flapping display flight. It lays 2–3 (rarely 4) olive-brown eggs in a bare ground scrape. These and the young are defended noisily and aggressively against all intruders (including humans) by means of threats, vocalizations and low flights. To fool those who approach, it employs the tactic of laying down in a different place, pretending that the eggs are there.

It is the national bird of Uruguay where it is called Tero. It utters a tero-tero call throughout day and night that is used as territorial displays, display flights, and courtship behaviors. A variation is used as an alarm call but at a higher repetition rate.

More Info: neotropical.birds.cornell.edu