Green Island Nature Reserve protects an important site for bird conservation and migration, just off Cape Sable Island. It is one of the most southerly points in Nova Scotia.

The island is exposed and un-forested. Large flocks of migrating shore birds use its grassy and shrubby terrain, boulder and cobble beaches, eroding banks, and small lagoon for staging and feeding. The island also provides nesting habitat for terns, sea ducks, gulls, cormorants, and Atlantic puffins.

With nature reserve designation, hunting is prohibited above the mean high water mark.