Some hummingbird species, particularly the rufous, travel thousands of miles. A crucial key to their tremendous vitality lies in their aeronautical body designs. Robust, lightweight structure comprising hollow bones, a narrow body, sleek tail, and narrow graceful wings. The physical ingredients for lengthy flights enable the bird to glide smoothly over the sky while expending the least energy.  In addition, the bird must also know the direction of its destination. It uses the sun's position, the earth's magnetic fields, or specialized proteins in their eyes.