The Extinction of the Passenger Pigeon

The Extinction of the Passenger Pigeon

This article relates to A Sand County Almanac

When we think about how pioneers changed the American frontier — or if we think about it — we may picture the hunting of bison herds as one of the biggest environmental changes wrought by settlers. The grainy photographs of thousands upon thousands of bison skulls piled unimaginably high, a near-extermination that seems mind-bogglingly cruel and ill-considered.

But extinction of the bison was caught in time, and today there are still herds roaming the Great Plains, albeit in very reduced numbers. A much less-known destruction that was even more massive and permanent was that of the passenger pigeon (Ectopistes migratorius) in the second half of the 19th century.

In his seminal environmental book, A Sand County Almanac, Aldo Leopold wrote a eulogy to these once-ubiquitous birds that numbered in the billions and migrated across much of North America. He used the example of their massive slaughter to decry his contemporaries' view that nature was a resource to be exploited solely for human gain:

"We know now what was unknown to all the preceding caravan of generations: that men are only fellow-voyagers with other creatures in the odyssey of evolution. This new knowledge should have given us, by this time, a sense of kinship with fellow-creatures; a wish to live and let live; a sense of wonder over the magnitude and duration of the biotic enterprise…These things, I say, should have come to us. I fear they have not come to many."

But what was a passenger pigeon? How could billions of birds be wiped out in just a few decades, ages before any of us alive today were even born?

It happened like this. Passenger pigeons traveled in massive flocks — groups so large that no non-human predator could seriously damage their numbers. It's an evolutionary tactic called "predator satiation." (Periodic cicadas, emerging in massive, neighborhood-covering swarms, are another example.) But after the Civil War, a commercial industry began to develop around hunters preying on these huge flocks, which facilitated over-hunting. At the same time, habitat loss through deforestation scattered the birds. As populations began to decline, breeding plummeted because passenger pigeons practiced communal breeding and roosting — meaning they successfully reproduced only when large flocks were intact. The double-whammy of hunting and habitat loss permanently damaged their ability to replenish their numbers, leading to an extinction spiral. As Leopold noted, "Like any other chain reaction, the pigeon could survive no diminution of his own furious intensity."

By the mid-1890s, populations had crashed to the point where the few remaining flocks couldn't breed successfully, and the last known surviving passenger pigeon, a female named Martha, died at the Cincinnati Zoo in 1914. Although this extinction and attempts to stop it — a few laws in the late 1890s aimed to prevent hunting but weren't enforced, conservationists tried to breed surviving birds — are largely forgotten, those who read A Sand County Almanac will learn about the destructive power of careless greed that led to the extermination of the species.

As our planet faces more mass extinctions due to climate change and habitat loss, it's a lesson we should pay attention to closely and immediately.

Frontispiece from a volume of articles, The Passenger Pigeon, 1907 (Mershon, editor)
Cropped version via Wikimedia Commons

Filed under Nature and the Environment

This article relates to A Sand County Almanac. It first ran in the January 29, 2025 issue of BookBrowse Recommends.