Unionized workers have gone on strike at Peru's top copper mine to protest a decline in income. It is the first strike since operations began 13 years ago at the Antamina mine owned by an international consortium including BHP Billiton Ltd., Glencore Plc., Teck Resources Ltd. and Mitsubishi Corp. Union leader Jorge Juarez says the 1,730 unionized workers who went on strike Monday account for more than half the mine's employees.