Medium-sized oropendola of montane forests. Evenly olive-green, with a dark eye and pale bill. Smaller than the similar Russet-backed Oropendola, with a darker olive head. Weaves hanging nests in small colonies, and is found most frequently around forest edges and flying above the canopy. Song is a variable jumble of liquid whistles and pops; listen also for its loud “chak” call notes.