Being one of the forty-three primates identified by Linnaeus in 1758, the Cotton-top Tamarin, Saguinus oedipus, has a surprisingly small range, a tiny corner of northern Colombia. It is one of the smallest primates, weighing about one pound. Its diet includes mostly fruit, insects and tree sap & gum and it is an important seed disperser in tropical forests. They can live over 20 years in captivity.
They are at the Bronx Zoo, in cages outside the Mouse House. When the tamarins were several feet back from the bars, I got these photos using a Nikon D5100 with a Nikkor 55-300mm zoom telephoto lens (focal lengths of 135mm and 260mm). The bars blurred out very well, more than I thought possible. Presumably direct sunlight was not hitting them.
Sometimes they will obligingly pose on the cage bars (shown below).
You can also photograph them at the Central Park Zoo, where they are behind glass (see three pictures below).
Note their claws, common to Marmosets and Tamarins, but unusual among monkeys, who generally have nails.