John Heinz National Wildlife Refuge at Tinicum is a unique, urban oasis where both people and wildlife can find their space outdoors. It is notably home to the largest remaining freshwater tidal marsh in Pennsylvania, known as Tinicum Marsh. The refuge has been designated as an Important Bird Area by the National Audubon Society. It’s diverse habitats provide a sanctuary for birds in Greater Philadelphia. Over 300 different species have been recorded here, with 90 species known to nest on the refuge.