Here in the Stupidest Timeline it is impossible to tell what is true any more, but we are expected to believe both that: coalmine canaries were only discontinued in 1986; and that the mining companies actually bothered building safety equipment for them.
My co-worker's dad was a miner in Yorkshire. He says there was still a law on the books that you had to bring a literal canary with you in a mine, but they had much more sophisticated detection equipment by then and no one wanted the canary to actually die.
I wonder how often they forgot to feed the canaries.
Rarely if ever I should assume. How often do farmers forget to feed their sheepdogs? Like a sheepdog, in theory these aren't pets, but the humans get sentimental about them.
They only brought male canaries, because they sing. Before dying, they stop singing, and that's presumably what they're listening for. Better to revive and recycle the bird rather than procure an endless supply of them.
How many hours have human laborers toiled removing fossilized carbon to the soundtrack of a single bird who doesn't know why it's so dark?