canary in a coal mine
Something whose sensitivity to adverse conditions makes it a useful early indicator of such conditions; something which warns of the coming of a greater danger or trouble by a deterioration in its health or welfare.
Meaning adapted from Wiktionary, available under CC BY-SA 4.0.
“Rising prices are the canary in a coal mine for the economy.”
“The sudden drop in local sales acted as a canary in a coal mine, warning the company of a larger financial crisis.”
“The rapid decline of the local bee population served as a grim canary in a coal mine, signaling that the entire ecosystem was facing an irreversible collapse.”
The term refers to the nineteenth- and early twentieth-century practice of carrying caged canaries into subterranean tunnels. The birds, possessing a higher respiratory rate and greater sensitivity to airborne toxins than humans, served as a primitive biological alarm.
If carbon monoxide or other lethal gases accumulated within the mine, the bird would succumb to the atmosphere before the miners were affected. The death of the canary provided a window of time for the workers to exit the tunnels immediately, the bird having performed its final service to the industry.
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canary fit
A highly emotional state of distress, anger, etc.
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carry coals to Newcastle
To do something that is unneeded or redundant.
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cat that ate the canary
A person who appears self-satisfied or smug, especially while concealing something mischievous, prohibited, or private.
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coals to Newcastle
A pointless venture, in the sense of sending something to a place where it is made, or where they already have an abundance.
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haul someone over the coals
To express anger with someone in no uncertain terms when they do something wrong.
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miners' canary
Any thing, especially an organism, whose demise or distress provides an early warning of danger.
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rake over the coals
To call to task or to reprimand severely.
Last updated August 10, 2026