Heron Island is treeless, primarily covered with herbaceous vegetation and patches of woody shrubs. The island is surrounded by granite boulders and ledges that range from gradually sloping to small steep cliffs.
Common Eider, Great Black-backed and Herring Gulls, Black Guillemot, Double-crested Cormorant, Leach?s Storm-petrel, and Great Cormorant all nest on the island. Harlequin Ducks use the near-shore habitats during the winter.
The rough shoreline, difficult access, and exposed location lessen the number of potential threats and reduce their severity. The potential for a hazardous spill or the problems associated with ballast discharge from the large number of cruise ships and Canadian-bound tankers that pass by the island all year poses a potentially serious threat. A full survey of nesting Leach?s Storm-petrels has not been completed.
The island has full conservation protection and is administered by Acadia National Park. It is closed to public access during the seabird nesting season (April 1 ? August 15).