When methane built up, or carbon dioxide built up, or oxygen was diminished, the birds would swoon before people would -- so it acted as an early warning system: Hey, get out of the mine. Things aren't going so well.
Kada bi se metan nakupio ili ugljik dioksid ili je ponestalo kisika, ptice bi se onesvijestile prije ljudi -- to je bio rani znak sustava: Hej, bježite iz rudnika. Stvari ne idu baš dobro.