edmund - sorry to distract, but what is a canari? Is it a byrd?"also serves as a canari."
canary in a coal mine:
"An allusion to caged canaries (birds) that mining workers would carry down into the mine tunnels with them. If dangerous gases such as methane or carbon monoxide leaked into the mine, the gases would kill the canary before killing the miners, thus providing a warning to exit the tunnels immediately."
Proxus