(Reuters) -Rio Tinto on Wednesday reported lower-than-expected iron ore shipments for the first quarter, as labour shortages and supply chain snags curtailed the global miner’s efforts to ramp up its Pilbara operations in Western Australia. The mineral-rich state lifted hard-line border curbs put in place to curb the spread of COVID-19 only in early March, leaving companies to battle for months a dearth of mine workers and train drivers even as pent-up demand fuelled a rally in commodities. Rio has also had to contend with a delay in production from a new greenfields mine, which led to a weake…