@Chlidonias The common name "Reed Titi" usually refers to C. modestus, AFAIK. I'm certain that these aren't White-eared Titis, since their colors are slightly different. Usually, White-eared Titis are gray with a reddish brown head, while these are more of a gray brown. It's easier to see them difference when you compare images, though.
The more I look into it, the more I'm convinced that they're not P. modestus. The colors do look a little different to me, but P. modestus is a red color. As disappointed as it is, these do seem to be White-eared Titis.
@red river hog - the only place (on Google) that I can see modestus being called "Reed Titi" is by a few American zoos, which actually have donacophilus - any other mention of the name which I can see refers to donacophilus.
It is also worth noting that C. modestus was described in 1939 from just two specimens, and then not recorded again until 2002, so it is extremely unlikely that any American zoos have been keeping modestus anyway.
