A Message from Martha by Mark Avery, book review: How did passenger pigeons disappear?

Passenger pigeons were once the most abundant birds in the world. They are now extinct. How did this beautiful species disappear?
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The Independent Culture

On the 1st of September 1914, somewhere between noon and 1pm, a passenger pigeon named Martha, a resident of Cincinnati Zoo and Botanical Garden, breathed her last. Her death was not unexpected; for several weeks her condition had been reported in the local press and a stream of visitors watched over her decline.

Yet at first sight Martha would not have appeared the most remarkable among the zoo's exhibits. Larger than the somewhat similar mourning dove, with a longer tail and wings, as a female she did not have the remarkable pinkish-orange breast of the male of the species, so notably absent from her enclosure. Interest in Martha's health and in her ultimate demise derived not from her appearance, but her status. As far as anyone could ascertain, she was the last surviving passenger pigeon in the world.

This then, was a very modern extinction, its precise timing duly noted in the ledger of loss and destruction accompanying the onward march of human progress. Martha's last wild cousin had been shot on 24 March 1900. A 14-year-old boy named Press Clay Southworth was feeding cattle when he spotted an unusual bird fly up into a tree and asked his mother's permission to use the family shotgun. When he presented her with the bird she immediately recognised it as a passenger pigeon, as any adult living in the eastern part of the United States at that time would have been bound to do. Within living memory, these birds had been the most common in the United States, the most numerous in the world. The sight of a flock of passenger pigeons on the move, or roosting in a breeding colony, was a natural phenomenon – a "biological storm" as Mark Avery terms it – on a par with any of the wonders of nature provided by the rapidly diminishing American wilderness.

Here is Major William R King, writing in 1866, a mere 34 years before Southworth pulled the trigger: "Hurrying out and ascending the grassy ramparts, I was perfectly amazed to behold the air filled and the sun obscured by millions of pigeons, not hovering about, but darting onwards in a straight line with arrowy flight, in a vast mass a mile or more in breadth, and stretching before and behind as far as the eye could reach. Swiftly and steadily the column passed over with a rushing sound, and for hours continued in undiminished myriads…"

Using calculation methods honed during his time as conservation director of the RSPB, the author arrives at an estimate of the passenger pigeon population of the US a century before its disappearance as between five and 10 billion birds. As late as 1857, an Ohio State Senate select committee decided that there was no need to protect the passenger pigeon, as "no ordinary destruction can lessen them, or be missed from the myriads that are yearly produced". Yet destroyed they were, in a remarkably short space of time, posing the central questions of this book: how was this achieved (for erasure on such a scale obviously required considerable effort); and what can such an ecological catastrophe teach us as we attempt to preserve wildlife in our own ostensibly more enlightened times?

The passenger pigeon was a specialised feeder, relying chiefly on the nuts of the American beech and American chestnut trees and the acorns of the red and white oak. The production of such "tree mast" varied, forcing the pigeons into the nomadic lifestyle. Before the arrival of Europeans they had evolved a survival mechanism called "the predator dilution effect". By congregating in vast numbers and nesting in colonies of as much as 30 square miles, in which individual trees bore 100 nests and birds roosted piled on top of each other, their combined weight causing branches to crash to the ground, the chances of any individual bird being predated were small.

Once established in breeding colonies, the pigeons made little attempt to evade capture. Native American hunters traditionally only took the fat-bound squabs, or pigeon chicks, but European settlers were less discriminating. In some of the most powerful passages of the book, Avery relates the industrialised harvesting of the pigeons that took place once the arrival of the railroad and primitive refrigeration techniques allowed large-scale meat export to the cities; one town in Ohio in 1876 shipped out 45,000 pigeons a day by train and boat. Guns, nets, arrows, decoys and saltlicks all played their part. Squabs were poked out of nests with sticks while fires laden with sulphur were lit at tree bases to make others jump to their deaths. A vast number of birds were wounded or killed and left to rot on the forest floor, surplus to requirements, turning the previously peaceful woods into an inferno.

Despite this onslaught, Avery concludes that it was the destruction of the pigeon's habitat, the great forests that once covered vast swathes of the US, that sounded its death knell. In his preface, he describes himself as "a scientist by training, trying to be a writer, after being a professional conservationist, and needing to be a bit of a historian to produce this book". In its science, its history and its ecological insights, the book excels; in the comparatively few passages where he is "trying to be a writer", perhaps less so. These include a diary of his own American journey, in which he proves himself a better, more interesting observer of bird than human behaviour; and imagined speeches by both the captive pigeon herself and Barack Obama, the latter promising protection for North America's wildlife.

These eccentricities aside, back in Northamptonshire, Avery's description of the 40 per cent decline in British birds over the past century, and the bone-headed refusal of farmers' leaders to endorse ecologically friendly farming methods, provide a chilling echo of his American discoveries. Will our own turtle dove follow the passenger pigeon into extinction over the next decade? Within the frame of this well-documented previous disappearance, such questions take on a new urgency. Martha's message rings out loud and clear.