Stop Cruel Death of Feral Chickens on island of Oahu

Sorry the picture is not of feral chickens.

The city of Honolulu has hired a contractor to round up feral chickens on the Hawaiian island of Oahu and kill them with carbon dioxide gas—but high concentrations of CO2 are extremely painful to birds and cause them great distress. PETA (People for the Ethical Treatment of Animals) and others have supplied this information to Mayor Kirk Caldwell’s office, but to no apparent avail.
There must be a humane solution!