Graphics Reference
In-Depth Information
We will take a more detailed look at wings and how they work later in the text
in the section covering the principles of flight and types of flying.
Small Birds
For the purposes of our discussion I include here only those birds that range in
size from the wren to the blackbird. Small birds such as hummingbirds, swifts,
swallows, and martins, which I have grouped together, have been covered
elsewhere.
It is easier for smaller birds to hover, but it's harder for them to fly at faster
speeds. Their wing-to-body ratio is more suited to sustained, powered flight.
Although their size and wingspan make them less suited to soaring or gliding
over long distances in the way larger birds do, their particular mode of flying
does allow them to glide over shorter distances during a flight. For some small
birds this results in a rather undulating flight pattern.
FIG 4.42
Small birds are capable of
hanging from the lightest and most
slender of branches and reed stems.
A bird's size affects the type of flight the bird is capable of, but it does not
affect its ability to travel over great distances. Many very small birds undertake
migration, some of them over huge distances. Metabolic rate in small birds is
higher than in larger birds, the extreme example being hummingbirds. During
cold weather smaller birds are far more susceptible to hypothermia, and in
particularly harsh winters mortality rates can be very high. Size also allows
birds to exploit different food sources. Many birds, such as the long-tailed tit,
