10/14/2014 04:19 pm ET Updated Dec 14, 2014

The Year of the Passenger Pigeon

The year of the Passenger Pigeon is fast coming to its end and the publicity generated by a variety of focus groups has resulted in the species becoming almost as familiar an icon of extinction as the Dodo. For those who don't already know, the Passenger Pigeon was once probably the most plentiful bird on earth. During early years of the nineteenth century great flocks darkened North American skies as the birds flew from place to place like huge clouds of locusts. The species occurred in unimaginably large numbers yet just 100 years later at the start of September 1914, the very last individual -- a bird its keepers called Martha -- died in its cage at the Cincinnati Zoo. So, this year has been something of an anniversary. There have been countless educational programs, magazine and newspaper articles, long series of lectures, even a vast mural painted on the side of a building in Cincinnati -- all to celebrate (if that is an appropriate word in the circumstances) this 100th anniversary. It has inspired three books: A Feathered River Across the Sky by Joel Greenberg, A Message from Martha by Mark Avery and my own more prosaically titled work The Passenger Pigeon. Even the Smithsonian Institution has got in on the act and taken Martha herself (she was stuffed after her death) out of storage. For reasons best known to museum curators she had been relegated to the Smithsonian's cupboards years ago. Now she is back on display, and the general public can see her once more.

All of this has generated much debate over the dramatic nature of the species' extinction and suggestions as to how it could, and should, have been avoided.

There were two primary reasons for the Passenger Pigeon's rapid and spectacular decline: the dreadful toll of over-hunting and the destruction of the forests in which the birds lived. But unless a species lives only in a restricted area (like a small island, for instance) it is difficult to actually hunt it to extinction. As it becomes rarer it becomes harder to find and therefore more difficult to shoot. If the species is to actually become extinct there are usually other, additional, factors that come into play. And therein lies the great mystery of the Passenger Pigeon. Why couldn't it survive in small numbers in the large stands of forest that were -- and still would be -- available to it? Many bird species that have declining numbers manage to do this.

It is a question that has mystified most commentators but it may, in fact, be easily explained. Once reduced to comparative rarity, the species' final eclipse was surely due to its peculiar breeding system. After a few days the adult birds simply abandoned their chick (they had only one in each breeding session) in the nest and just flew off. Following a period of forlorn chirping, the helpless baby would climb out of the nest and flop to the ground where it would remain for a day or two until it was capable of flight. It is easy to imagine what would happen: predators from all around would gobble up the entirely defenseless chicks until they were utterly sated. But when there were literally millions of chicks there would still be millions left once the stomachs of the local predatory population were filled. Now picture the scene if there was a flock of only 50 or 100 birds. The equation is simple. The chicks drop from the nest and flap around the forest floor. Soon, very soon, they would all be gone. Every one!

Conservationists always ask for lessons to be learned from the past, and have suggested that the story of the Passenger Pigeon points us to solutions. But does it? Is there any truly meaningful lesson to be learned? Sadly, in the case of this particular species, extinction may have been unstoppable; due to the peculiarities of its way of life the bird was absolutely incompatible with the coming of the technological human. Even if we disregard the dreadful effects -- and the appalling nature -- of the over-hunting, the vast areas of forest necessary to the species' survival were as doomed as the bird. It was inevitable that forests would be chopped down at a frantic rate to make room for the great invasion of European newcomers. Idealists may regret this, but It is entirely unrealistic to suppose there could have been any other outcome. There were simply too many people with too many needs arriving on North American shores. And the idea that had the species been protected it could have somehow survived in remaining areas of forest is equally unrealistic. This was not a bird that could replicate itself alongside huge numbers of humans, and due to its lifestyle it was not a creature that could creep away to live in small numbers in the heart of those forests that still remained. Even if some DNA wizardry allowed us to recreate the species, there would be nowhere left for it to go!

Can all the publicity the Passenger Pigeon has received change this kind of imbalance? For other creatures, animals that lead different kinds of lives, the answer is -- perhaps it can. But not in the case of a species that had evolved in such a unique direction.

In four years there will be another anniversary. It will be 100 years since the last Carolina Parakeet died, curiously in the same Cincinnati Zoo as Martha. Will the same conservationist song be sung over again? Probably -- and In this case there may be lessons from the past that can actually be applied to the future.