Graphics Reference
In-Depth Information
a perfect illustration of this method used on water; albatrosses do a very
similar thing but they run along the ground, preferably into a headwind.
Landing
Getting airborne is one thing, but landing demands a very different approach
to flying. The need in this instance is for a bird to shed speed in a very
controlled manner so that it can land safely. Landing requires a lot less energy
than taking off, but it also demands a good deal more control. Accuracy is
critical if the bird is to avoid injury and come to rest exactly where it intends.
Some birds find this process more straightforward than others. The ease of
landing often depends on the surface on which the bird needs or prefers for
landing. The timing of landing is critical; birds need to arrive at the required
landing spot at the very moment they have ensured that their airspeed is zero.
FIG 4.55
Sequence of a small
passerine (starling) landing on a
feeder.
Landing on the ground is the only option for some birds. Large birds find
this more difficult than smaller ones because they have more momentum
that is difficult to shed. In coming in to land geese often undertake a steeply
angled, high-speed descent by executing a maneuver called
whiffling
that
involves a rapid series of alternating sideslips in which they twist their bodies
to extreme angles, shedding any lift on the wings. This enables the geese to
shed height at a high rate.
