Butterfield is continuing its share buy-back programme, purchasing another $1 million worth of common shares last month.In a filing with the Bermuda Stock Exchange, Butterfield announced that during the month of April it purchased for Treasury 1,080,774 common shares at an average cost of $1.40 per share.The bank said no 8% preferred shares were bought in April for the share buy-back programme.Butterfield shares closed last week at $1.45. Their 52-week low has been $1.22.