The passenger pigeon

How did a bird species that once numbered in the billions disappear from the face of the Earth?

In spring 2014, in anticipation of the centenary of the passenger pigeon's extinction, Radio Canada featured the Redpath Museum's two mounted specimens in a program called “La résurrection de la tourte disparue depuis un siècle”. What we learned from this broadcast was that in the 18th and 19th centuries the passenger pigeon was the most abundant bird species on Earth.

The first European drawing of the species, in the Codex canadensis (left), was made by the Jesuit missionary Louis Nicolas in the early 1700s. He wrote a brief description of what he witnessed: “Oumimi, or ourité, or dove. One sees such great numbers of this bird at the first passage in spring and fall that it is incredible.”

Passenger pigeons were easy to catch because they stayed together in large flocks and perched on the lower branches of trees. They were considered an easy source of food because they could be beat out of their perching branches with sticks and then bagged. In 1866 in Ontario, it was reported that one flock of birds, 300 miles (482 kilometres) long and one mile (2 kilometres) wide, darkened the skies for 14 hours as they flew by overhead. Unlike the domesticated carrier pigeon used for messages, these were wild birds. Even their feathers were popular for bedding; for a time in Saint-Jérôme, Quebec, every dowry included a bed and pillows made of pigeon feathers. By 1900, there we no passenger pigeons left in the wild. By 1914, there was just 29-year-old Martha at the Cincinnati Zoo. Then on September 1, 1914, Martha was found lying dead on the bottom of her cage. The passenger pigeon was now extinct. It had gone from billions of birds to zero in about a century, probably less.

What happened to the passenger pigeon?

According to an article in Arstechnica, which reviewed several scientific studies on passenger pigeon genomes and population fluctuations, the demise of the passenger pigeon is more complicated than was once thought. It seems their population ping-ponged regularly and, according to McGill herpetologist David Green, the bird’s disappearance is partly attributable to the Allee effect, a behavioural phenomenon where certain types of animals require the presence of other individuals to thrive.

“Her mate died a few years before her,” Green said. “When large populations of bird species like passenger pigeon, or even large groups of breeding frogs like the chorus frog, fall below their sustainable threshold size, they can’t recover."

Despite the Allee effect, the chief cause of extinction for the billions of passenger pigeons was the destruction of eastern North American forests and hunting.

“It was the first time we could be certain that humans had caused a species’ extinction,” said Green.