phrase
Canary in the Coal Mine
An early warning sign โ the one that suffers first when something invisible is going wrong.
Origin
From a real practice: British coal miners carried caged canaries underground from the late 19th century until the 1980s. Canaries have rapid metabolisms and small bodies, so they succumb to carbon monoxide or methane long before humans notice. A silent or dead canary meant evacuate.
Modern usage
Used for any small, sensitive signal that warns of a larger threat โ a churned customer, a quiet engineer, a bird species disappearing. The original practice was retired when electronic detectors took over.
Tags
warning
indicator
history