Biology Reference
In-Depth Information
times they were made into primitive flutes, which have since been recovered from caves.
Charles Darwin had a pipe whose stem was made from the hollow wing of an albatross.
Many of the avian bones that are equivalent in origin to human bones are reduced
and fused into forms unlike our own. For example, the bones corresponding to our finger
bones have been fused and modified to support all the primary flight feathers. Birds also
have some vertebrae that are fused together to form a rigid plate of bone that widens lat-
erally to fuse with the pelvic bones. The entire structure makes a light, stiff framework
that allows a bird's legs to support its body with a minimum of heavy muscles.
Flying birds have a huge, keel-shaped sternum protecting the chest and part of the
belly from physical blows while providing a perfectly placed surface for attaching the
large wing muscles. The backbone, ribs, and sternum together form a flexible but strong
box, housing and protecting the heart, lungs, and other major organs.
Some birds such as woodpeckers and blackbirds may cruise forward on a powerful flap
or two and then soar for a moment, wings folded, before the next flap. This gives them
an undulating flight pattern.
Q Flying seems like such a great thing. So why can't Ostriches and penguins and
some other birds fly?
A
Flyingisasplendidability,butitcomesatacostintermsofmaintainingahugekeelon
the sternum and large flight muscles. Most ratites, the group to which Ostriches belong,
seem to have lost flight in order to increase their body size and the strength of their legs
and feet. They can outrun most predators, and some can kick hard enough to disembowel
dog-sized predators.
Penguinsdohavestrongwingsandstrongpectoral muscles topowerthem. Inasense,
theyreallydofly,exceptit'sthroughwaterratherthanair.Penguinbodiesarestreamlined
as if for flight, which allows them to cut through the water with the least resistance.
Buttherequirements forrapid,poweredswimming aredifferent fromthoseforflying.
To dive deep and do the things penguins do in the water, and to survive the frigid air
temperatures that many of them must endure, their bodies have huge fat supplies, heavy
muscles, and extremely dense (and heavy!) feathers. That makes them too heavy to fly
with such small wings.
