The Indian River estuary lies immediately east of Pleasant Bay and is dominated by two-mile long Crowley Island, bordered along its entire east side by over 350 acres of tidal mudflats and fringing salt marshes. Crowley Island's wetlands are particularly important because they attract huge assemblages of migratory shorebirds and wintering and migratory waterfowl, notably Black Ducks. Keeping eastern Crowley Island undeveloped and undisturbed is critical for shorebirds that depend on the flats where they fatten in preparation for long non-stop migrations, as well as for waterfowl feeding to meet their wintertime energy requirements. Crowley Island's intertidal habitats have been designated by the State of Maine as:

• High Value Feeding and Roosting Shorebird Habitat
• High Value Tidal Waterfowl and Wading Bird Habitat

The island's uplands offer attractive habitat for resident ruffed grouse and migratory and nesting songbirds as well as for deer, moose, coyote, black bear and other furbearing animals. Crowley also has extensive prime American Woodcock habitat that is undergoing an ongoing habitat refreshment program initiated by PRWF during the winter of 2008/09.  The project is designed to enhance feeding, roosting and nesting conditions for Woodcock, a species in decline across its entire historic range as a consequence of habitat loss.

The threat of subdivision for second homes became acute on Crowley Island when a bridge connecting the north end of the island to the mainland was completed in 1996 and several homes were constructed on the northwest side of the island. 

Becoming concerned about the negative impact of potential residential development along the eastern shore, in 2003 PRWF acquired two large contiguous parcels, protecting three miles of shoreline, 300 acres of upland and more than 150 acres of intertidal wetlands.  Downeast Coastal Conservancy holds a conservation easement on another 58-acre parcel on the southwest tip of Crowley Island. 

For walkers or cross-country skiers, a rough and unmaintained woods road offers access to the interior of the island.  Deer and upland bird hunters also reach the island’s isolated woodlands along this route. The public boat launch on the Addison Basin Road offers direct access to the protected waters surrounding the island for kayaks, canoes and outboards.