How Did the Canary Come To Be Associated With Coal Mines?

Canary in coal mine cage

Humans have been mining since prehistoric times, when flint was excavated for its use in tools and weapons. Since then, we have gone on to mine all manner of minerals, from copper and gold to the rare earth elements used to create the components in many of our modern devices.

Yet mining, and underground mining in particular, is extremely dangerous, with risks such as cave-ins, explosions, toxic air, and extreme temperatures. It may seem strange, then, that such a risky profession is associated with the small and spritely songbird Serinus canaria, otherwise known as the canary.

Just how did this tiny, tuneful member of the finch family become connected with going deep down into the perilous dark of the world’s coal mines? Well, as it turns out, we owe quite a debt to this brave little bird.

The link between canaries and coal mines began with the British physiologist and philosopher John Scott Haldane (1860-1936), a pioneering specialist in the physiology of respiration. Haldane’s many contributions to the field include his investigations into decompression sickness, which helped to improve safety for undersea divers, and an early gas mask designed to protect soldiers against poison gas in World War I. And it was Haldane who first proposed an innovative safety measure for miners. Following his investigation into the cause of an 1896 explosion at Tylorstown Colliery in Wales, Haldane concluded that carbon monoxide buildup was to blame for the disaster. So, he suggested using mice or birds to monitor gas levels in the mines, as he knew that these animals were far more sensitive than humans to poison gases.

Heeding Haldane’s recommendation, British miners began taking canaries into the coal mines — carried in small metal or wooden cages — to detect the presence of odorless carbon monoxide. If the canary showed any signs of distress (or if it suddenly died), it was a clear sign to the miners that conditions were unsafe and the mine should be evacuated. The use of canaries in this way is perhaps the most common example of what is known as a sentinel species, a term applied to animals or plants that serve as harbingers of danger to human health or the wider environment.

It wasn’t long before the use of canaries in coal mines became commonplace not only in Britain but also in the United States and Canada. The birds became such a trusted part of the mining process — part of the team, you could say — that miners were known to treat their avian companions almost as pets. In some cases, special cages were designed for the canaries that could be used to resuscitate the poor little birds should they succumb to noxious gases. These metal-and-glass cages were fitted with a small oxygen tank. If the canary inside began to show signs of carbon monoxide poisoning, the cage door was closed and a valve opened to revive the bird with a fresh supply of oxygen.

Canaries were used in British coal mines for almost a century. Then, in 1986, hundreds of canaries breathed a collective sigh of relief when Britain announced that the use of birds in coal mines would stop, to be replaced with modern detectors, often known as “electronic noses.” But to this day, canaries retain their connection with coal mining, as much a symbol of the profession as coal-blackened faces, hard hats, and pickaxes. The canary’s role in the mines was so significant that it also became ingrained in the English language: The common idiom “a canary in the coal mine” is still used to refer to something that gives an early warning of danger.