Can a pitcher be charged a fielding error?

Yes. Once the pitched ball is batted, a pitcher becomes a fielder. If he makes an attempt to field a ball and rightfully should be able to score a putout but fails, he can be charged a fielding error. One example would be a bunted ball where the pitchers moves to pick it up with his glove, but instead hits it away from himself, allowing the batter-runner to safely reach first base. The pitcher made an attempt to field the ball and should have had the batter out, but he failed.