Rosemary and peter grant of princeton university have studied finches on the galapagos islands since 1973. they found that when drought conditions on the islands increased, the seeds produced by some of the plants that provided food for the finches were affected. the drought decreased the supply of plants that produced easily cracked seeds, but permitted the survival of plants that produced larger, tougher seeds. only finches with strong, wide beaks could break open the tougher seeds. w