The Yellow-billed Cacique is a unique icterid. It is not a cacique, in fact in the icterid family tree it lies on a branch all by itself at the base of the Cacique-Oropendola clade. That is to say, this is the oldest branch in the group, it is neither a cacique nor an oropendola, but is related to that group. The Yellow-billed Cacique is all black and has an ivory white bill that almost shines in the dark undstory habitats preferred by this species. It also has a long and broad tail that is often frayed at the ends, probably from sneaking through dense habitats. The bill itself shows a flattened culmen and the tip is chisel-like, also the nostrils are covered by a sheath for protection, in some ways the bill resembles that of a woodpecker and this is by no coincidence. This icterid feeds by pecking at twigs, branches and bamboo to get access to insects within. Interestingly in some parts of its range it is an absolute bamboo specialists, while in other areas it takes undergrowth but does not need bamboo. One of the bamboo loving populations is in the highlands of Costa Rica, the other in the highlands of South America, while some lowland intervening populations are not bamboo loving. This suggests that bamboo specialization may have arisen twice separately perhaps? Surprisingly given that this icterid is in the cacique-oropendola group, it makes a classic cup-shaped nest, not a hanging pendulous nest as the rest of the group does.