12 Who can discern the nature of the birds of the air? How some carry with them a voice of melody, and others are variegated with all manner of painting on their wings, and others fly up into mid air and float motionless, as the hawk: for by the Divine command the hawk spreads out his wings and floats motionless, looking towards the south. What man can behold the eagle's lofty flight? If then you can not discern the soaring of the most senseless of the birds, how would you understand the Maker of all?
Source: Catechetical Lectures (New Advent)