3 individuals observed; same individuals as @upupamartin observation
Horned Guan
Oreophasis derbianus
El Triunfo cloud forest, Chiapas, Mexico
19 March 2003
Very low light conditions so this is the best I could do. The image is not sharp, but it is the only one I got.
This is one of the world's rarest birds with perhaps 500 in existence. I have been fortunate enough to lead perhaps a dozen trips to see it between 1987 and 2005 so I've seen it many times but only had camera equipment a few times.
Hidalgo County, Texas, US