FEATURE A bronze Martha attracts visitors to her memorial aviary and reminds people of the scale of the loss (Mark Avery)
On 1 September 1914, when a Passenger Pigeon named Martha died in Cincinnati Zoo, Ohio, the world lost its most abundant bird species for ever. The Passenger Pigeon’s Ectopistes migratorius extinction was about the 100th avian extinction since 1500 (and there have been c.30 since) but its loss represented the passing of more individual birds than all those other 129 avian extinctions put together. Martha lived and died in captivity, but only 60 years earlier the skies over the forests of eastern North America would darken as flocks of Passenger Pigeons numbering billions passed overhead. The descriptions of immense flocks of Passenger Pigeons by the likes of John James Audubon and Alexander
12
Wilson from the early decades of the 1800s strain our imaginations to grasp the numbers of birds involved. The accounts of these two famous “American” ornithologists (the first a Frenchman and the second a Scot—but both doing their ornithological work in the USA) give numbers of a billion and two billion respectively and are sufficiently detailed that we can check their maths, if not the observations on which they were based. A later, less well-known account of a flock of Passenger Pigeons, by an English soldier stationed on the Canadian side of the Niagara River, came from the mid-1800s; it appeared to involve a spring flock of around three billion birds. Many other accounts describe the sky darkening as the flocks
passed by, stretching from one horizon to the other for hours or days at a time. Unless the witnessed flocks included all the world’s Passenger Pigeons in one place, at the same time, then we simply do not know what proportion of the total population was involved. The Passenger Pigeon was a nomadic species because of its dependence on the acorns, beech mast and chestnuts of the eastern North American forests from southern Canada down to Florida and Texas. The almost extinct American Chestnut (wiped out by a fungal disease imported to the USA in 1904 but formerly abundant and widespread) produced its seed in fairly regular quantities each year, but the oaks and American Beech produce their acorns and beech mast
periodically in abundance, depending on weather conditions around flowering time. Tree mast production is synchronised over large areas of hundreds of square kilometres, but the locations of plentiful acorns and beech mast vary from year to year. Passenger Pigeons scoured the forests to search for those rich areas of food; they then nested in enormous colonies where food was abundant. The main breeding range stretched from southern Canada to Kentucky and Virginia, bordered by the Atlantic Ocean on the east and, roughly speaking, the Mississippi River to the west. In winter, the pigeon flocks moved south to forests where the absence of snowfall allowed the ground to be cleared of
WorldBirdwatch