I understand what the idiom means: as per this question, it means a person or creature unwittingly used as a test for danger, often destructively.

I understand why coalmines: as depositories of ancient organic waste, they are particularly prone to methane and carbon monoxide buildup.

But why a canary? They are technically exotic, native and (at least originally) endemic to the sub-tropical Canary Islands, which gave them their name. They were also renowned for their singing voice, as found out in this answer, and could presumably be quite expensive.

So why would a mining company in Britain and/or America and/or any other English speaking country use such an expensive and exotic bird as a glorified carbon monoxide detector whose sole purpose in life was to suffocate to death? Why wouldn't they use sparrows, or starlings, or some other small songbird native to the area? Are canaries just that easy to breed and keep? Are they super-extra-sensitive to poison gases and thus were the "upscale" model? Were all small, caged songbirds called "canaries" as a matter of course?

Or did the modern idiom simply opt for alliteration over historical accuracy?

closed as off-topic by David Richerby, Edwin Ashworth, nohat Aug 21 at 15:34

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    The first of your questions is not really on topic here (it’s more of a history matter), but the second one is. I would suggest editing the question to focus more on the language question and less on the history question, otherwise there’s a good chance this will be put on hold as not being about the English language. – Janus Bahs Jacquet Aug 20 at 23:05
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    @JanusBahsJacquet Thank you for the suggestion. After thinking it over, I may just have to migrate it over to History SE. – No Name Aug 20 at 23:22
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    When they were first brought to Europe (in the 17th century) they became "exotic and expensive" because the breeders who produced them only sold male birds (the females do not sing) and hence maintained their monopoly status on breeding them. Around 1900, one of the largest breeders in the UK was exporting about 10,000 canaries a year to the USA. Like most finches, they are very easy to breed in captivity - you just put a flock of them in a large outdoor aviary and let them do what they do naturally! – alephzero Aug 21 at 9:30
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    I'm voting to close this question as off-topic because it is about the history of mining, not the English language. – David Richerby Aug 21 at 11:45
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    Very interesting comments about History. Actually I think you will find it is not History. It is a while since I perused the laws on Coal mining but the last I was aware it is still necessary by law to keep Canaries at a coalmine. I was formerly in charge of the colliery electrical department (surface) and the aviary came under my jurisdiction. – Brad Aug 21 at 13:54

Canaries were not only used in coal mines. The old Normanby Park steelworks in Scunthorpe had an aviary as late as the mid twentieth century where they bred canaries for gas detection purposes. They were so good at breeding that they showed the best looking birds (and probably the best singers) in competition with other breeders.

A caged canary would be taken in into an area where CO and other dangerous gases might be present; if there was a concentration of dangerous gas the bird would pass out and fall off its perch but would usually recover quickly after it was removed from danger.

Because they are quite easy to breed in captivity canaries, although an introduced species, have been quite cheap to buy and keep in the UK. Before the introduction of canaries as pets caged linnets were often kept for their song, but I believe that they were captured from the wild rather than bred. Interestingly country people who couldn't afford parrots (which were and are expensive) would sometimes keep captured jays or jackdaws as pets for their mimic abilities.

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    In a rural environment "capturing" corvids like jackdaws is hardly necessary, since wild corvids can recognize individual humans and learn which ones are not threatening to them. I used to have a "pet" wild crow that would look through the house windows till it found the room I was in and then tap on the window to beg for food, and come into the house to eat from a plate on the floor. It was never "trained" to do any of that. I guess it had seen me outside often enough to decide that I wasn't a threat to it. – alephzero Aug 21 at 9:45

The metaphor is historically accurate: actual caged canaries were historically brought into coal mines.

The breeding of canaries in captivity in Europe started in the 17th century, and thus predates underground coal mining. By the time underground coal mining started, caged canaries were already available. Their smallness, and the smallness of the cages, [edit: and (as Guntram Blohm points out) their constant singing,] made their use as carbon monoxide and methane detectors effective, as well as practical.

According to the Smithsonian Magazine, the mining tradition of using canaries in coal mines to detect carbon monoxide and other toxic gases dates back to 1911.

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    1911 seems surprisingly recent, especially given sources like ia800501.us.archive.org/7/items/worldswork28gard/… talking about the ubiquitous use of mice and canaries in 1914. – origimbo Aug 21 at 9:51
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    Given that the Davey Safety Lamp for detecting methane was invented in 1815 I think that 1911 is a typo. – Martin Bonner Aug 21 at 10:03
  • Hmm. Having read the article, the 1911 date is not a typo. Maybe the use of canaries to detect specifically CO dates to 1911, and earlier it was more about methane. – Martin Bonner Aug 21 at 10:08
  • Um. Coal has been mined basically forever. – David Richerby Aug 21 at 11:44
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    Notably though, the canaries did not typically "suffocate to death". They merely passed out and stopped singing. Once removed from the mine, they usually recovered, and the miners were very protective of them. – Darrel Hoffman Aug 21 at 13:32

Male canaries will sing all the time when they're alone in the hope of their song attracting a female. In fact, the main reason for them being held in captivity is their incessant song.

This makes them ideal for coal mines; you don't have to concentrate on them or watch them. You do your work, register the canary's song as a background noise, and as soon as the background noise stops, you know you're in trouble.

  • Too bad all the noise from the drilling and hammering in close quarters with lots of audible reflection causes miners to lose their hearing ... ! Yikes. :) – Ian MacDonald Aug 21 at 13:31
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    @IanMacDonald That's OK -- the system fails safe. The deaf miners can't hear the canary so they leave the mine. – David Richerby Aug 21 at 15:13
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    @IanMacDonald I don't think that coalmines were quite so noisy before mechanisation. Much harder physical work then but the hand tools wouldn't have made nearly so much row, no rotary cutters, no conveyor belts and no jackhammers just men smacking away at the coal face with picks and the occasional gunpowder explsion. – BoldBen Aug 22 at 19:12

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