(Reuters) - KFC parent Yum Brands Inc on Wednesday reported a sharper-than-expected 13 percent drop in March sales at established restaurants in China as the country's new bird flu outbreak took a big toll on sales. The fast-food operator reaps more than half its overall sales in China, where most of its nearly 5,300 restaurants are KFCs. Yum was already struggling there because of a food safety scare last year. The average of four analyst estimates complied by Consensus Metrix had called for Yum's China same-restaurant sales to drop 10 percent. Shares in Yum fell 2. ...