Pico de plata (Arg, Bol), Viuvinha-de-oculos (Br), Viudita negra de bañado (Uru), Pico blanco (Par), Run-run (Ch).
♂ Black with white primaries, creamy bill and bare yellowish eye-ring. ♀: Darker yellowish eye-ring, slight pale eyebrow. Upperparts streaked; underparts buff with greyish streaking on breast. Rufous primaries.
Wetter tall grass areas near marshes.