Swift in Name—Swift in Flight
BY “AWAKE!” CORRESPONDENT IN KENYA
RACING THROUGH THE AIR on sickle-shaped wings flies one of the fastest living creatures on earth. It is a small bird weighing but a few ounces [up to a few tens of grams], yet it can move through the sky at high speed. “Swifts have been credited with air speeds of over 100 miles (160 km) per hour,” states The Encyclopedia Americana. No wonder these feathered speedsters are appropriately named swift!
The flight of swifts seems effortless as they soar high above the earth, turning and banking at breakneck speeds in their search for insects. Swifts are the most aerial of birds, catching food, eating, drinking, collecting nesting material, and even mating while in flight. They spend so much time flying that observers in ancient times believed that swifts roosted in the heavens, somewhere unseen in the clouds. Some swifts can be airborne for up to nine months of the year. These amazing little birds apparently even sleep while gliding in flight!
Designed to Fly
Swifts are marvels of aerodynamic design. They possess efficient crescent-shaped wings that curve backward and eliminate much of the drag that slows the flight of most birds. When aloft, they accelerate using rapid, shallow wingbeats with intermittent short glides.
Their unusual maneuverability is partly due to their ability to beat one wing faster than the other in flight. Beating the wings slightly out of phase enables swifts to make sharp turns without a reduction in speed. This permits them to attain great swiftness as they wheel about overtaking flying insects and scooping them up with their gaping mouths. Swifts must consume large quantities of insects in order to fill the massive energy requirements of their fast-paced life. And these nimble fliers can cover hundreds of miles a day in their search for insect prey.
The swifts’ humble appearance belies their outstanding flying skills. Both male and female are unimpressive, most of them a dull gray or brown in color. The many types of swift are found throughout the world and can be observed primarily in tropical and subtropical lands. In winter those that inhabit the Northern Hemisphere migrate thousands of miles to warm climates.
Nests of Glue
Swifts make their nests using a very unlikely building material—their own saliva! Possessing specialized salivary glands, they can produce large amounts of saliva that acts as a bonding agent for nesting materials.
Swifts seldom land on level ground, and they cannot perch as other birds do. Their legs have tiny hooklike feet and are so short that they cannot lift the bird high enough for it to make a complete wingbeat. However, their feet are ideally suited for clinging to vertical surfaces, such as cliffs, caves, and walls of buildings. When the time comes for building a nest, the swift cannot gather leaves, sticks, or mud from the ground, as is common with other birds. It must find another way.
The chimney swift gathers small twigs by swiftly flying through the branches of a tree, grabbing hold of a twig, and snapping it off with the force of its momentum. It then glues the twigs together, cementing them to a vertical surface with its sticky saliva. The American palm swift moves nimbly through the air snatching hairs, feathers, and bits of cotton and other light, floating material, which it uses along with its saliva in building a nest.
Another swift has been aptly called the edible nest swiftlet. Its nest is made almost entirely of its own hardened saliva. For centuries the saliva making up these nests has been the main ingredient of the delicious bird’s-nest soup enjoyed in the Orient. It is reported that millions of nests are used every year for this gastronomic delight.
One of the most interesting nests is made of the gluelike saliva of the African palm swift. This tiny bird glues a small flat pad of feathers to the underside of a palm leaf. Hanging upside down, the nest is often blown wildly in the wind. How does the tiny egg stay in the nest? David Attenborough, in his book Trials of Life, explains: “It seems almost impossible that the single egg could remain in the tiny cup. Indeed, it would certainly fall out were it not for the fact that the bird has not only glued the nest to the leaf, but the egg to the nest.” With both nest and egg firmly fixed to the palm leaf, the parents grip the sides of the nest with their claws and take turns incubating the egg. After the chick hatches, it clings to its windblown nest home until it develops flight feathers and takes to the air.
It is a delightful spectacle to behold thousands of swifts flying in high-speed swirls, twittering loudly as if with excitement. Watching them from below, one feels a sense of awe at their freedom of flight as well as appreciation for the beauty of their intelligent design. Indeed, it is easy to see why these aerial acrobats, with their great agility and speed, are truly deserving of the name swift!
[Pictures on page 17]
Common European swift
Animals/Jim Harter/Dover Publications, Inc.
[Picture on page 17]
© Robert C. Simpson/Visuals Unlimited
[Picture Credit Line on page 16]
© D. & M. Zimmerman/VIREO