"This year has been the centenary of the extinction of what used to be the most numberous bird on earth – the Passenger Pigeon. Passenger Pigeons once darkened the skies above the forests of eastern North America as their huge flocks searched for the acorns, beechmast and chestnuts on which they fed throughout the year. Many accounts mention flocks, a mile wide, passing overhead for hours or days at a time, crossing the sun and darkening the land as in an eclipse."