Job 39:26 - Ellicott's Commentary On The Whole Bible

Doth the hawk fly? — The more symmetrical order of these descriptions would be for the ostrich to have come after the war-horse and before the hawk; in that case there would have been a gradual transition from the fleetest of quadrupeds to the fleetest of birds by means of the ostrich, which, though winged like a bird, cannot use its wings as birds do, but only run on the ground like a quadruped.