A vast array of birds and marine invertebrates seeks refuge each year at the Port Mahon Preserve. This 341-acre marsh is surrounded on three sides by refuge lands, and by the bay on the fourth side. Migratory shorebirds seek refuge here every spring on their way from Central and South American to the Arctic breeding grounds. During the course of a week's stay at the refuge the birds can literally double their weight by feasting on an abundance of horseshoe crab eggs.

Horseshoe crabs are humble, ocean-living creatures that inhabit Port Mahon Preserve by the thousands. During the high tides that occur during the new moon, these blue-blooded creatures crawl onto shore en masse and lay countless eggs in the sand and silt.

• Take a stroll here during the spring, at high tide, to witness the great spectacle of thousands of horseshoe crabs clambering ashore to lay their eggs.
• Visit again in the fall to watch the soaring, migrating raptors.
• Keep an eye out for red knots. You can identify them in flight by their whitish rump, which is finely barred with gray.