A variety of birds are grouped together under the name «babbler». Some of them appear to bear little relationship to the others while a few can be fitted, only with difficulty, into the classification of birds. The 250 or so species of babblers are, accordingly, placed with the warblers, thrushes and flycatchers, which they most nearly resemble, within the large family Muscicapidae.
In general, babblers are poor fliers with short, rounded wings and fairly long tails. They live near the ground, searching for berries and insects. Some species are drab but others have brilliant markings. The smallest is the size of a wren, the largest the size of a crow. Their name comes from their continuous loud and varied calls.
The babblers are divided into six tribes: the jungle babblers, the scimitar babblers and wren babblers, the tit babblers, the song babblers, the wren-tit and its relatives, and the rock fowl, picathartes. Not all authorities agree that the last two should be classed as babblers, but there is no obvious other place for them.
A well-known member of the song babblers is the red-billed leiothrix or Pekin robin, as it is more popularly called. The Pekin robin is very much like a European robin in build, but slightly larger. Its plumage is olive green with red and yellow markings on wings and throat. The bright colours and an attractive song have made it popular as a cage bird. Despite its name the Pekin robin comes from the Himalayan region of India and southern China. The closely-related and slightly larger silver-eared mesia of the Himalayas and southeast Asia is also a cage bird. It is more brightly coloured than the Pekin robin, with a black head and silver-grey patches on the ears.
Life in dense forests
Babblers are mainly inhabitants of the Old World and are abundant in India, China and southeast Asia, extending to New Guinea, Australia and Africa, including Madagascar. The only American babbler is the wren-tit which lives on the Pacific coast from Oregon to Baja California.
The habits of babblers are very like those of the anthirds of the New World, living near the ground in dense forests, where they search for food in the undergrowth and the leaf litter. Although basically different in their anatomy, and bearing no relation to each other, the babblers and antbirds resemble each other in their weak flight and short rounded wings. This is an example of convergent evolution, where two unrelated groups of animals living in different parts of the world have both developed the same habits and have come to look very alike. The two main features of this convergence are probably linked with the similarity of the habitat; birds living in dense forests do not need powerful flight, indeed, the long wings, necessary for this, would be a disadvantage among dense foliage. Strong legs for walking or hopping in and out of the undergrowth are needed and both babblers and antbirds have these.
Outside the breeding season, babblers congregate in flocks, often of several species, which is another habit they share with antbirds.
When in their non-breeding flocks, babblers regularly form «clumps», like the avadavat in which the birds huddle together on a perch. They also preen each other. This kind of behaviour probably helps to keep the group together as does their continual babbling song, which informs every member of the flock where its fellows are while they are moving in dense forest.
Nest built of woven cobwebs
At the beginning of the breeding season certain flocks split up into pairs which spread out and take up territories, defending them against other pairs, or, in other species, pairs may remain together in parties throughout the breeding season. Nests are built near the ground and are well hidden by vegetation. Some species build open-cup nests while others build domed nests with entrances in the side. A feature of many nests is the delicacy of the materials used: lichens, spiders’ webs and the skeletons of leaves.
The wren-tit’s method of building the nest was studied in detail by an American ornithologist, and sheds light on how a bird can weave a stout, compact nest, firmly attached to a foundation of a forked branch or spray of twigs, with only its bill to manipulate the material. The wren-tits took a week to build their nests, which were made of bark fibre bound by cobwebs. First, a saucer-shaped network of cobwebs is woven between the twigs to form the foundation, Strands of web are then crisscrossed from twig to twig until a platform of considerable thickness is achieved, when bark fibres are also introduced. These are torn from old and weathered parts of stems, held in the bill and stripped backwards. When the platform is about an inch thick, the birds can sit on it while they work. Bark fibres are than placed around the rim and held in place by webs.
Spiders’ web is ideal for nest material because it is sticky, so there is no difficulty in anchoring the ends. Similarly when pieces of web are placed together they stick, and the platform becomes a solid structure. The wren-tit holds the bark fibres in neat bundles in its bill when collecting them, so when these are placed on the rim of the nest they fall naturally into place. They are held by a mass of web placed on top, strands of which are teased out and anchored at various points so that the bark is strapped down. Finally, the loose ends of the bark are tucked in and secured with more web. When the nest bowl has been completed, it is lined with bark fibre and decorated on the outside with pieces of lichen.
Wren-tits raise one brood a year from a clutch of three to five eggs. The young leave the nest when 2 weeks old and start hopping around nearby twigs, learning to fly a little in another week. When 5-6 weeks old they can fly well and hunt for their own food and help their parents defend the territory.
In species where the flock stays together in the breeding season, communal breeding may take place. Little is known of the breeding habits of many babblers but some, including the silver-eared mesias, jay thrushes and yuhinas, have been seen to share a nest between more than one pair. Several birds may build a nest together and several females lay in it, while the young may be fed by any member of the group.
One morning a strange bird was brought into the camp of Cecil Webb, who was collecting animals in the Cameroons for the London Zoo. It was a most unusual-looking bird with a bare, but brilliantly coloured head. Immediately Webb realised that he had a great rarity. It was a grey-necked picathartes or rock fowl. He was one of the few Europeans to have seen one alive, and he was even more lucky because this one had been caught in a spring trap designed to catch porcupines. Somehow it had escaped having its legs broken and the villager, who had caught it, intended to eat it but had brought it into the camp on the off chance that it might be wanted.
There are two species of picathartes, the grey-necked and the white-necked. They are the size of magpies and both have brilliantly-coloured bald heads. When they were first found at the beginning of the nineteenth century they were thought to belong to the crow family and were called bald crows. A century later they were moved to the starling family and only in 1951 was it suggested that they ought to be classed as babblers. Such uncertainty about the birds’ relationships is not surprising, because they were known in Europe from only a few skins in museums. The grey-necked picathartes, in particular, has hardly ever been seen alive. When Webb tried to find out more about it, he learned that even the woodcutters working in the forest had never seen one, probably because the picathartes is even more an inhabitant of dense undergrowth than the other babblers. Strangely, it nests on rock faces, and these must be rare in the jungle. After a painstaking search Webb managed to find a small ravine with six large mud nests on the side of an overhanging face. These were the nests of picathartes. They were empty but they posed the problem of how a bird, more at home on the forest floor, could build its nest on a face more suited to a swallow.