Saguinus oedipus.
There were formerly two large willow trees on the island, but both have now fallen or been cut down. Fortunately many new shoots have sprouted, so the tamarins have plenty of cover.
@Great Argus Not that I am aware of. They do have a hut for shelter and night quarters and they are very aware of their surroundings. There are always gulls in the area plus waterfowl and pelicans. Probably the only avian predators in the area that might take one are common buzzards - but they mainly hunt for rabbits in open areas. Several UK zoos keep marmosets and tamarins on islands or in open-topped enclosures.