Ominous Doomed Passenger Pigeons

[cronus]

http://www.newscientist.com/article/mg2 ... Agbn8VdU1I

Beautiful but doomed: Demise of the passenger pigeon

THIS September marks a melancholy anniversary: the first of the month is the centennial of the death of Martha the pigeon in Cincinnati zoo and, with her passing, the extinction of the passenger pigeon. It was an extinction that 100 years earlier would have been inconceivable.

This was a species that moved in flocks of billions of individuals, so dense as to blot out the sun and take days to pass. Birds pausing on trees did so in numbers sufficient to break the boughs under their weight. Luckily, while they fed on a wide variety of fruits and seeds, passenger pigeons preferred mass-fruiting species such as chestnut, whose branches were large, dense and fecund enough to support the enormous numbers.

They were superbly adapted to long-distance flying, and ranged over much of eastern North America, moving in a perpetual search for food. The pause for reproduction was brief, annual and occurred in colonies that covered thousands of hectares.

The passenger pigeon was among the most abundant bird species that ever lived. Yet a combination of trapping, shooting and collecting young birds to eat, plus the destruction of its habitat, occurred on such a massive scale that eventually Martha was all that was left. And then she was gone.

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So what can we learn from the demise of the passenger pigeon? The take-home message must be that of the tipping point, the moment beyond which movement to a new stable state is the only option. As the species adapted, psychologically and biologically, to only breed in large crowds, it was doomed once its population fell below a critical threshold.

As seas acidify, glaciers melt and forest cover fragments, I can't help wondering how many Marthas humanity is pushing towards non-recoverable change. And whether we, the most abundant primate that ever lived, may one day, equally unexpectedly, share her fate.

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