I had never heard the expression ‘canary in a coal mine’ until this morning while listening to the radio. I looked it up and thought I’d share what I learned in case you had never heard it either.

Back in the day, coal mines had no ventilation and toxic gases could build up. Canaries are very sensitive to methane and carbon monoxide so miners would bring a caged canary to work and knew it was safe as long as the canary was whistling.  The expression means now refers to the signs of things to come.