The USGS Acadia National Park bird checklist provides letter codes denoting the habitat where one should expect to find a particular species. The assorted habitats include deciduous forests, open fields, salt marshes, offshore islands, evergreen forests, coastal regions, freshwater marshes and lakes. The checklist assigns a letter to the bird if it typically resides in just one or two kinds of habitat. For example, the spruce grouse has an "E" next to its name, meaning it will normally only be in the evergreen forests of Acadia.
Another facet of this checklist is a number system that lets the user know how common a bird is in Acadia National Park during each month of the year. Twelve columns corresponding to each of the 12 months contain numbers from 1 to 4. An abundant species earns a 4 rating, and the birder should expect to find it without difficulty in the appropriate habitat during that time frame. Common birds have a 3 assigned to them, which means these birds are in their habitat but not in huge numbers. Uncommon species are there in certain portions of their habitat and have a 2 attached to them. The 1 rating goes to birds rarely seen on the island. Birds with no number in a monthly column do not live in Acadia National Park during that month.
List of Rare Birds
There is an extensive list of birds that birdwatchers have reported on Acadia five times or fewer. These birds' infrequent appearances on the island make it very exciting if you do positively identify one there. Diverse species such as the tundra swan, sandhill crane, varied thrush, white-eyed vireo, gadwall, Chuck-will's-widow, willow flycatcher, lark bunting and Connecticut warbler are on this list.
A birdwatcher would naturally expect many types of seabirds to occupy a checklist of birds on Acadia National Park. Jaegers, gulls and terns are on this list along with shorebirds like plovers and sandpipers. Birds of prey like the osprey, bald eagle and northern goshawk hunt in Acadia. Game birds like the ring-necked pheasant and ruffed grouse are year-round residents. Owls like the great horned owl and woodpeckers such as the downy woodpecker make Acadia their home and do not migrate during the cold winters. Some of the species that do head south when the cold creeps in are the warblers, thrushes, swallows and flycatchers.