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| Sunday, 12 February 2006 |
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Junior Observer |  |
| News Business Features Editorial
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Avian home builders Birds are not only unique animals because they are endowed with feathers, but also unusual animals, and scientists are divided as to what creature they might have evolved from. We know that the first birds appeared during the time dinosaurs lived.
Archaeopteryx is accepted to be the oldest bird, following a fossil found in a German quarry. It is believed to have existed 150 million years ago! Based on this bird's features; the reptile like teeth, bony tail and claws along its wings, some scientists are of the view that these birds evolved from reptiles. However, other scientists believe that modern day birds are flying dinosaurs! Since the early birds, many thousands of different species have evolved, fascinating man with not only their beautiful physical features, but also their varied behaviour. Today, we focus on a major aspect of their behaviour, which makes them different from other animals, (with the exception of mammals), because of the care they take over rearing their young. The most obvious example of this behaviour is nesting. The building of a secure home in which to brood eggs and raise chicks, is very important, and birds are very good at this. The 'homes' they build range from simple scrapes in the ground, to intricate, elaborate and complex designs, making nest building one of the most difficult bird behaviour to understand.
We know that a basic bird's nest consists of large and small twigs. The large ones are used to make the frame, and the smaller twigs are placed in- between to bind it all together. The lining of the inner bowl of a nest differs from one bird to another, but most birds use feathers, grass, leaves, spider webs and plant remains. As birds are resourceful creatures, they have learnt to use all kinds of material to build their nests, such as, string, plastic, coir and even wire. The nests are made in the ground, in crevices, on trees on vertical surfaces and even in shallow water. Some nests are camouflaged and well protected, while others are made out in the open. Some of the types of nests birds build are scrape nests (shallow depressions made in the ground), burrow nests (very effective at protecting eggs and young), cavity nests, platform nests (relatively flat nests located on the ground, in a tree or on the tops of rooted vegetation and debris in shallow water), cupped nests and hanging and woven nests.
Nest building is primarily instinctive, but it has been noted that older birds are better nest builders, revealing, that experience does count! Out of the large number of birds that inhabit this world, which birds do you think build the largest nests? The Golden eagle and the bald eagle. Built from twigs, the bald eagle's nests weigh up to three tonnes. The Golden eagles build new nests on top of the old ones, and this results in huge nests after a period time. However, the mallefowl's incubation mounds can contain over 50 tonnes of earth, making them the largest nests of all birds.
The tailor bird is one of the most skilled nest builders in the world. Its beak is long and thin like a needle. The bird uses it as a tool to stitch two leaves together and create a pouch for its eggs. And what do you think it uses as thread? Spider's silk which is one of the strongest in the world. Now, which bird in the avian world would get the prize for making the smallest bird nest? The vervain hummingbird of course. Its nest is no larger than a halved table tennis ball. The rufus ovenbird, a native of South America, is named after the shape of its nests, which resemble the traditional ovens of Argentina and Paraguay. And guess what the raw material is - a mixture of straw, mud and cowdung. Once the nest is made, it dries in the sun, making it very hard, so that no predator can break it open. Other birds that use mud to build their nests include the rock fowl, swallows and martins. Have you heard of birds that make their nests using their saliva? The Swifts and swiftlets have large saliva glands which produce glue that holds their nest material - mud and straw together. Cave swiftlets from Southeast Asia make their entire nest from saliva. Local people use them for 'bird's nest soup'. The high prices paid for these nests make them the world's most vulnerable nests. Verdins are small industrious birds that build nests throughout the year. They build several nests at the same time; 'roost' nests and 'brood' nests. The roost nests are used as temporary homes, until they build the proper nest where they bring up their young. Their nests are very distinctive. They are almost round, and the size of a grapefruit, with the opening on the side or bottom. Weaver birds use grass to build their nests. Some weaver birds don't build new nests every year. Instead they use the old nests from the previous year for the basis of the new construction, with fresh blades of grass, intervowen with dull, brown grass. Reed warblers weave grass to make nests. Most birds take great pains to build their nests, but not all birds build elaborate nests. The fair tern simply lays its eggs on the branch of a tree, and the Arctic tern scrapes a hollow out of pebbles to lay its eggs. Woodpeckers use trees and even wooden pillars. There are some birds that use others' nests to lay their eggs, and even let the foster parents take care of the young. Falcons use abandoned nests of pigeons or crows, and the bird called dikkop, from Africa, nests on the sun-dried droppings of hippos! So, it's evident that the birds will use any material to build their
nests. Find out more about birds and their nesting habits, because you
will be simply amazed at their innovativeness. However, birds are not the
only ones in the animal kingdom who build nests. Many other animals too do
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