Pea Patch Island, just a half-mile off Delaware City's Battery Park, is home to a large colony of herons, with Fort Delaware on the southern end and nine species of wading birds settled on the marshy, forested northern tip. This heronry, or rookery, provides a safe haven for thousands of migrating birds, with 3,000 to 4,000 birds annually. The National Audubon Society and BirdLife International designated it a "Continentally Important Bird Area." Delaware's Department of Natural Resources and Environmental Control protects the birds by restricting access to their nesting area, while visitors can walk from the fort to the edge of the preserve and use an observation tower to watch the birds during the spring and summer months. According to legend, the mile-long island, covering nearly 300 acres, got its name when a ship loaded with peas foundered in the mud, spilling its cargo, and the peas sprouted, took root, and gradually built up the island. The heronry attracts many species of wading birds, including herons, egrets, and ibis, whose long legs and necks allow them to feed on aquatic creatures in the shallow waters around the island's shores and riverbanks.