With common bird populations on the decline, these birds are “the canary in the coal mine,” said Ken Rosenberg, ... The species' appearance is among the most variable in North America.

They’re sensitive to invasive species and land management. ... Vonnegut mentioned his “canary-bird-in-the-coal-mine theory” again in a 1973 interview with Playboy.

Forget the canary in a coal mine: today the danger zone is the entire U.S., and the sentinel species comprise a growing list that includes the Golden-cheeked Warbler, the Florida Scrub Jay and the ...

Mining foreman R. Thornburg shows a small cage with a canary used for testing carbon monoxide gas in 1928. George McCaa, U.S. Bureau of Mines Never mind the gas—it was automation that got them ...