This is most likely Wanton Island.
Edgar Mayhew Bacon In The Hudson River From Ocean to Source relates the history of Wanton Island. The legend is that it was the site of a battle between the Mohawks and the Mohegans over who would name the next chief or sachem. Bacon says:
"After a day of hard fighting, according to Indian methods, the Mohegans succeeded in driving their enemies from the field. The Mohawks then retreated to another island, where they built fires and pretended to encamp. But, having spread their blankets upon poles near the fire, so that they should resemble men seated there, they retired to the forest and waited in ambush until the Mohegans appeared to complete their victory. The Latter, stealing up in the dead of night, tomahawk in hand, fell upon the unsuspecting blankets with great fury. While thus exposed in the glare of firelight, and no doubt thrown into confusion by he ruse that had duped them, they fell upon a ready prey to the arrows of the crafty Mohawks."