During a few August and September weeks, hundreds of thousands of tree swallows collect in vast murmurations at the mouth of the Connecticut River. With metallic blue-green wings and white breasts, tree swallows trace the air for insects. After feeding, the thick avian sky drops to rest on shoreline phragmites where the birds cling through the night. Generations of swallows annually stage here before journeying south.
The disappearance of birds in winter was, at one time, a mystery. Aristotle thought birds hibernated, and as late as the seventeenth-century, many assumed swallows wintered beneath rivers and lakes. It’s hard to believe the preposterous theory was accepted, but there were no birds in winter, and the idea that they would go south en masse to return months later sounded similarly absurd.
The famed ornithologist Roger Tory Peterson, who saw the Connecticut River event late in life, called it one of nature’s greatest spectacles. Seeing it, then returning a month later to the cold spot left empty, troubles even a modern credulity.