Possible Clues:

• Fly very low
• Fly close to the ground
• Insectivore not quite last to trap fly close to earth
• Fly at very low altitude
• Fly a crop duster
• Creature stops short, quietly, seeing fly near the ground
• Not go the way of a highflier?
• High-fliers won't lay off hard work
• Fly close to ground (in plane)
• To be evasive, bound to fly low