The area of the park along the Harlem River includes Muscota Marsh, one of Manhattan's last remaining natural salt marshes, the other being Smuggler's Cove, which attracts large numbers of waterbirds. These waterfowl can be studied further via educational programs held at the Nature Center at the north end of the property. Mallards, Canada geese and ring-billed gulls are year-round residents, using both the water and the nearby lawns and ballfields. Many wading birds and waterfowl pass through on the spring and fall migrations, and herons and cormorants often spend the summer. Also in the salt marsh can be found fish, mollusks and crustaceans among the cordgrass and bulrushes which can tolerate both salt and fresh water.