A trip to the Outer Cape isn't complete without a visit to the Massachusetts Audubon Wellfleet Bay Wildlife Sanctuary, an 1,100-acre haven for more than 250 species of birds attracted by the varied habitats found here. The jewel of the Massachusetts Audubon Society, the sanctuary is a superb place for walking, birding, and watching the sun set over the salt marsh and bay. The Esther Underwood Johnson Nature Center contains two 700-gallon aquariums that offer an up-close look at marine life common to the Cape's tidal flats and marshlands. Other rotating exhibits illustrate different facets of the area's ecology and natural history. From the center you can hike five short nature trails, including a fascinating Boardwalk Trail that leads over a salt marsh to a small beach -- or you can wander through the Butterfly Garden. Note that as of this writing the center was closed for repairs and reconstruction, and there's no timetable in place as to when it will reopen -- check first before going. The center's interpretive programs are still in place, however, and the sanctuary remains open for hiking.

The Audubon Society is host to naturalist-led wildlife tours around the Cape, including trips to the Monomoy Islands, year-round. There are bay cruises; bird, wildlife, and insect walks; hikes; snorkeling; winter seal cruises; and birding, canoe, and kayak trips. The sanctuary also has camps for children in July and August and weeklong field schools for adults. Phone reservations are required for some programs.