winnow

verb (used with object)

to free (grain) from the lighter particles of chaff, dirt, etc., especially by throwing it into the air and allowing the wind or a forced current of air to blow away impurities.
to drive or blow (chaff, dirt, etc.) away by fanning.
to blow upon; fan.
to subject to some process of separating or distinguishing; analyze critically; sift: to winnow a mass of statements.
to separate or distinguish (valuable from worthless parts) (sometimes followed by out): to winnow falsehood from truth.
to pursue (a course) with flapping wings in flying.
to fan or stir (the air) as with the wings in flying.