The Casqued Oropendola is a relatively small, stocky oropendola restricted to the lowlands of extreme western Amazonia, where it is largely confined to eastern Ecuador and eastern Peru, and is only found within reasonably dense forest. It seems to be largely dependent on seasonally flooded forests, at least for nesting, but the birds certainly range into terra firme forests in order to forage. The body and wings are largely chestnut-colored, but the breast and neck sides are olive-yellow, and the throat is slightly grayish. Both the primaries and the rectrices show prominent yellow edges. Both sexes of Casqued Oropendola possess whitish irides and a prominent pale casque to the bill. The species’ loud, sometimes even raucous calls often provide the first clue as to the Casqued Oropendola’s presence.