Identifying Edible Chestnuts
You are most likely trying to determine whether your tree is a horse chestnut (Aesculus hippocastanum) versus a sweet chestnut (Castanea sativa). American chestnut (Castanea dentata) was once common in southern New York State but has been almost eradicated by chestnut blight.
Ignore what the animals around you are doing.The chemical tolerance of squirrels and chipmunks is not an effective determinant of toxicity to humans. And while the nut of a horse chestnut tends to be smoother than the more pointed sweet chestnut, individual fruits can vary, so examine several before making a determination. If you are in any doubt, don't eat the nuts.
It is much more likely that you have a horse chestnut on your property as they are more common in yards and sweet chestnuts more common in woodland. Here is how to confirm that is the case.
A horse chestnut has a 5 to 7 lobed palmate leaf with pointed, serrated leaflets (pictured below). Deer and other mammals do eat the fruit but humans should not.
A sweet chestnut has a single serrated and pointed leaf with prominent veins (pictured below). The nuts are found in clusters and are smaller than a horse chestnut. Bark on an older tree will have spiraling fissures.
-Courtesy of NYBG Plant Information Service