The gifts of birds

23rd March 2001 at 00:00
Birds are among nature's most wonderful creations. They make beautiful music, build complicated architecture, and fly huge distances across the world. Samm Kweku Richardson considers the amazing abilities of different species.

Birds are among the most resourceful and graceful creatures in the world. Their great instinctive knowledge makes them excellent musical virtuosos, expert nest builders, and incredible migrators and navigators. Their inherent ability to fly has taught mankind great lessons in aviation.

Birdsong is a wonderful phenomenon. Some birds produce intricate musical notes that keep human listeners spellbound. The American Mockingbird is capable of mimicking as many as 55 other birds in an hour and the rhythm of its melodious outpouring is amazing. Another example is the Musician Wren of South America. As with other tropical bird pairs, the male and female communicate beautifully with each other by singing duets - either the same song together, different parts of the same song alternately, or different songs entirely. What makes their performances extraordinary is that the timing is so precise that the whole sounds as though it was sung by one bird.

Birds are also architects and builders. Nest-building is an art that involves a fascinating sequence of actions. Each of the different species the world over has its own peculiar habits and attitudes regarding choice of location for building the nest, selection and combination of building materials, the architecture and the volume of effort invested. These birds are all guided by instinct in building their nests. Let us consider a few species and their approach to the business of nest building.

The Tailorbird of Southern Asia makes thread from cotton or bark fibres and spiderweb, splicing short pieces together into longer lengths. It punches holes with its beak along the edges of a large leaf. Then, using its beak as a needle, it pulls the two edges of the leaf together by means of the thread, similar to the act of lacing up shoes. When it gets to the end of the thread, it either ties a knot to hold it fast or splices on a new piece and resumes sewing. In this way, the bird turns the big leaf into a cup in which it makes the nest.

One species of Swift makes its nest using saliva. Before the breeding season starts, the salivary glands swell and produce a viscous, mucous secretion. With its arrival comes the inherent knowledge of what to do with it. They smear it on a rock-face and, as it hardens, smear on more layers to make a cup-shaped nest. Another species of Swift makes a nest the size of a teaspoon, glues it on to palm leaves and then glues the eggs into the nest.

The Weaverbirds of Africa use grasses and other fibres to make hanging nests. They use a variety of woven patterns and knots in building what may be likened to an apartment house. They initially make a thatched roof about 15 feet in diameter in strong tree branches, and to the bottom of this, many pairs attach their nests. More than a hundred may be sheltered under one roof.

The Horned Coot usually builds its nest on a small flat island. If it cannot find one, it makes its own island. In this case, it identifies an appropriate place on the water and then begins to carry stones there in its beak. The stones are piled up in water that is about three feet deep until an island is formed. The base may be 13 feet in diameter and the heap of stones may weigh more than a ton. The Horned Coot then brings vegetation on to this stone island to build its large nest.

The Hornbills of Africa and Asia select a cavity in a tree. The female uses clay to seal up the opening until she can just squeeze through. Once she is inside, the male brings her more mud and she closes the hole until only a slit remains, through which the male feeds her and the bbies. When the male can no longer bring sufficient food, the female breaks out. The opening is then repaired by the young birds and both parents bring them food. Several weeks later, the fledglings break down the wall and leave the nest.

The Penduline Tit's hanging nest feels like felt because the bird uses downy parts of plants and grasses. The basic structure is made by weaving long grass fibres back and forth. The bird pushes the ends of the fibres through the mesh with its bill. Then it takes shorter fibres of downy material which it pushes into the weaving, in a manner somewhat like the technique of oriental carpet weaving. These nests are strong and soft, and havebeen used to make children's slippers.

Birds are unrivalled migrators and navigators. They follow different migratory patterns, fly at different heights and in different formations, depending on their species. Their varied flights are fascinating. Indeed, birds possess an astounding power to fly over long distances without losing their track or bearing between their point of departure and their chosen destination. What accounts for this?

Scientists have found that many creatures, including birds, have particles of magnetite in their heads. This substance is used to make compasses, and its presence enables birds to sense the earth's magnetic field, thereby charting a definite course for their journeys. As well as using these built-in magnetic compasses, birds also make use of the sun and stars for directions.

Here are just a few examples to demonstrate the migratory and navigational powers of birds: The Arctic Tern, nesting north of the Arctic Circle, flies south at the start of the northern winter to spend the Antarctic summer months on the pack ice near the south pole. They circle the entire continent of Antarctica before heading north to return to the Arctic, thus completing a yearly migration of roughly 22,000 miles.

The Blackpoll Warbler has a brain as small as a pea and weighs only three-quarters of an ounce, yet it travels from Alaska to the eastern coast of Canada in autumn, gorges on food and stores up fat, taking off when a cold front comes. It first heads towards Africa, flying at an altitude of up to 20,000 feet over the Atlantic Ocean. Then it picks up a prevailing wind that turns it towards South America, its final destination. In this trip of about 2,400 miles, the Blackpoll Warbler is governed entirely by instinct .

White storks spend summer in Europe, but fly 8,000 miles to enjoy winter in South Africa. The Ruby-throated Hummingbird, remarkable in view of its tiny size (9cm) and weight, migrates almost 600 miles across the Gulf of Mexico, beating its tiny wings up to 75 times a second for 25 hours. Over six million wingbeats without stopping!

Birds' ability to fly is a great marvel. Aircraft design has benefited immensely from the study of their wing curvature, which gives the lift needed to overcome the downward pull of gravity. The leading edges of the wings have "flaps" of feathers that pop up as wing tilt increases. These flaps maintain lift by keeping the main air stream from separating from the wind surface.

Another feature which mitigates the effects of turbulence and prevents stalling is the alula, a small bunch of feathers that the bird can raise up like a thumb. Airplane designers have adopted many of these features in the various flaps and projections which serve as turbulence spoilers or braking devices.

By observing birds we can understand some of nature's mysteries. As written in the Book of Job, chapter 12 verses 7-8, "Even birds and animals have much they could teach you; ask the creatures of the earth and sea for their wisdom."

Samm Kweku Richardson is a freelance writer and advertising consultant based in Accra, in Ghana, West Africa.

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