Never mind the gas—it was automation that got them in the end.

On this day in 1986, a mining tradition dating back to 1911 ended: the use of canaries in coal mines to detect carbon monoxide and other toxic gases before they hurt humans. New plans from the government declared that the “electronic nose,” a detector with a digital reading, would replace the birds, according to the BBC.

Although ending the use of the birds to detect deadly gas was more humane, miners’ feelings were mixed. “They are so ingrained in the culture, miners report whistling to the birds and coaxing them as they worked, treating them as pets,” the BBC said.

At the time, it was the latest of many changes in the British mining industry, which was a source of great strife in the country through the 1980s. Pit ponies, the other animal that went underground with human miners to haul coal, were also phased out by automation. The last of them retired in 1999, wrote Clare Garner for The Independent.

The idea of using canaries is credited to John Scott Haldane, known to some as “the father of oxygen therapy.” His research on carbon monoxide led him to recommend using the birds, writes Esther Inglis-Arkell for Gizmodo. He suggested using a sentinel species: an animal more sensitive to the colorless, odorless carbon monoxide and other poisonous gases than humans. If the animal became ill or died, that would give miners a warning to evacuate.

Why was a canary Haldane’s suggested solution? Canaries, like other birds, are good early detectors of carbon monoxide because they’re vulnerable to airborne poisons, Inglis-Arkell writes. Because they need such immense quantities of oxygen to enable them to fly and fly to heights that would make people altitude sick, their anatomy allows them to get a dose of oxygen when they inhale and another when they exhale, by holding air in extra sacs, he writes. Relative to mice or other easily transportable animals that could have been carried in by the miners, they get a double dose of air and any poisons the air might contain, so miners would get an earlier warning.

Britain wasn’t the only place to adopt Haldane’s suggestion. The United States and Canada both employed canaries, as these images from the Department of Labor show. Miners are pictured holding the birds in small everyday cages and returning from the scene of an explosion with a canary in a special cage intended to resuscitate the bird after exposure.

The modern carbon dioxide detector is certainly a less romantic image than a canary in an overused saying. Remembering the canary, though, is an opportunity to remember a world of coal mining that no longer exists.