Definition of "guan"

The 'true' (Penelope) guans also occur at a range of altitudes but like most species of cracids, are mostly restricted to forest, both montane and lowland. Piping-guans (Pipile) are primarily lowland species, whereas numerous monospecific (single-species genus) taxa of guans (i.e. Aburria, Penelopina, Oreophasis) are restricted to montane environments.

2000, Daniel M. Brooks, Stuart D. Strahl, Curassows, Guans and Chachalacas: With Spanish and Portuguese Translations, page 8

Most guans move among only the most rewarding trees, those having the largest fruit crops and/or the greatest reward per fruit. Nevertheless, solitary individuals and some guan groups - as well as the first-mentioned guans, once they deplete the fruit crops in the most popular trees - are stuck with the less rewarding trees.

2002, Kent H. Redford, Peter Feinsinger, “17: The half-empty forest: sustainable use and the ecology of interactions”, in John D. Reynolds, editor, Conservation of Exploited Species, page 381

The Crested Guan is a large, brown, turkeylike bird most frequently seen peering down from the treetops as it searches for fruit and leaves that make up its diet. As its name implies, this bird has a feathered crest that is frequently raised as it relates to nearby guans or to potential danger.

2010, Carrol L. Henderson, Birds of Costa Rica: A Field Guide, page 40