I'd never seen a Crested Guan. Formerly they were common from Mexico to northern South America, but they are large, turkey-like birds and have been hunted so thoughtlessly that over most of their former distribution area they've been wiped out. You can see the handsome bird at http://www.greglasley.net/crestguan.html.
So, toward dusk I was hiking through a very dense, shadowy stand of Mexican Cypress trees (Cupressus lusitanica) with a few oaks (Quercus affinis). Suddenly out of the chill gloominess there erupted several very loud, sharp QUONK-QUONK-QUONK calls almost like the sound of a wet finger stroking a wet balloon. Then there was heavy flapping and movement all around. Six to eight Crested Guans moved away from me from the ground and low branches to higher branches, looking like they didn't really want to fly, taking their time getting away and glancing over their shoulders as if hunters and guns didn't exist. In this light they looked totally black and the size and shape of Wild Turkeys, but with very conspicuous, bright-red wattles. Books show them with lines of white speckles on their chests but I would have sworn they were totally black.
Another few minutes of walking brought me into another flock sounding and behaving the same.
At dusk, in the bottom of a dark little valley, I set up my tent on a solid floor of acorns beneath Quercus affinis. The acorns were small so my bed didn't feel nearly as uncomfortable as it sounds. The moment I pulled the sleeping bag's hole shut there came a QUONK. Then more, then many more, stereophonic QUONKING, gloriously surrounded by birds I'd never chanced to see until this very Christmas Day!