Sporting notebooks, binoculars, and gaiters, birdwatchers are thick on B.I. in the fall. Though 13 miles offshore, the island is considered a top-notch birding destination. Over 250 species land here each year.
The apparent origin of the flyway that includes B.I. was the melting of glacial pack ice over 10,000 years ago. Vegetation began taking hold along this chain of newly exposed islands, including the Elizabeth Islands, Martha’s Vineyard, and Cape Cod, and species of birds began expanding their springtime migrations northward. During the same period, shorebirds also pushed north, where they thrived along newly formed sandbars, shoals, and tidal channels.
Inclement weather is one reason migrating species land here; the island presents a safe layover for birds pushed off course by winds blowing in the wrong direction. Additionally, the island’s varied and plentiful vegetation allows migrating birds to refuel their highly stressed bodies. Thickets of shadbush, chokecherry, bay, and blackberry offer first-rate sanctuaries.
Rolling meadows at the Lewis-Dickens sanctuary (southwest corner of the island) are an ideal habitat for many species, such as the extremely rare grasshopper sparrow. Because of thermals rising from oceanside cliffs, the south end of the island is also a Mecca for birds of prey like kestrels, peregrine, and merlins. Diverse topography at the maze, west of Clay Head Trail, attracts an array of species all year long.
Spring and fall are the best seasons for birdwatching. In summer, look for shorebirds while walking the beaches in the morning and at low tide. Look for herons and egrets around salt marshes.