Miner's canaries

Canaries have not always been cared for as much as today; in the old days, they were used as a living warning system for odourless toxic gasses, especially carbon monooxide, in mines. A miner would have a cage with three or more canaries in it with him when exploring a new shaft, and if any of them behaved abnormally, the miner determined that shaft was unsafe.

What do you think about this?
I think it is another absolutely disgusting display of humans thinking they're the only beings worth anything.

Its not right at all poor lil birdies. Most of them would die in response to the toxic gases

I agree with the above.
At least give them a chance to escape danger - don't keep them in cages. That way, if they leave, you'd better too.