How Birds Begin Their Flight: Taking Off from the Ground
The leap of the folded legs joined to the first wingbeats, and launching from a descent
Continuing the section on birds, Leonardo examines how a bird begins to fly when standing on level ground. In one mode it crouches, then springs from its bent legs into the air and, at the top of the leap, drives its wings down to climb obliquely stage by stage; in a variant it raises the wings obliquely first, or lowers the wings and extends the legs at the same instant so that the combined power of the leg-thrust and the first wingbeat is the greatest available. A second general mode occurs when a bird launches from a height, throwing itself forward with wings opened up and forward before rowing them down and back to follow an oblique descent. Small marginal sketches show a bird detaching itself from the ground.
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Springing from crouched legs to climb obliquely
To begin flight from level ground the bird first lowers its body to the earth, then with a very swift extension of its folded legs generates a leap into the air. At the top of the leap the wings finish their upward extension and at once beat down toward the ground, so the bird rises to a second oblique stage, and so on to whatever height it pleases.
Leg-thrust joined to the first wingbeat for maximum power
Some birds, once crouched with wings raised up and forward, lower the wings and stretch the legs in one and the same instant. Thus the power of the first wingbeat, added to the power of the leg-extension, becomes very great; this united power is the maximum that can be made at the beginning of these birds' flights.
Launching by descending from a height
The second manner birds use to begin flight is when they descend from high to low. These simply hurl themselves forward and at the same moment open the wings up and forward; in the course of the leap they lower the wings down and backward, and so, rowing, they follow their oblique descent. Others launch with closed wings and open them in the fall.