The thrushes are a large and widespread group of birds with few characteristics that clearly distinguish them from related groups such as babblers, flycatchers, and warblers. There is thus no easy definition of thrush, but most of them show the follow-in features: they have I o primary feathers, of which the outer one is much reduced in length; the tarsus (shank) is “booted” (not divided into separate scales on the leading edge); the juvenile plumage is spotted; they build cup-shaped nests; and they typically forage on the ground for animal food, sup-lamented with fruits taken from trees and shrubs.
Most of the thrushes that have been well-studied are similar in their social systems. Monogamous pairs defend nesting territories in the breeding season; in resident species, pairs may remain together all year. In the non-breeding season, thrushes tend to be highly social, feeding in flocks and, especially in cold weather, roosting communally; but some migratory wheat ears defend feeding territories in their winter quarters.
The larger thrushes may defend their nests pugnaciously, and one among them is unique in the way in which it does so. Fieldfares nest semi-colonially (an unusual habit in the sub-family) and attack predators which approach their nests by flying at them and “bombarding” them with their feces. you\AT shave been known to become so plastered with feces in this way that they have been unable to fly and eventually have succumbed to starvation.
With some 6o species, the true thrushes constitute by far the largest genus in the subfamily. They occupy a central place in that they appear to be unspecialized and show the basic type from which the various more specialized groups have radiated. Moreover, they are familiar to almost everyone, since in every continent except Australia there are at least one common garden species. No other genus of land birds is so widespread.
Eurasia is especially rich in species, the Song thrush, Istle thrush, and blackbird being among the best-known European birds. Their place on garden lawns and playing fields is taken by, for example, the Olive thrush in southern Africa, the Rufus-bellied thrush in Brazil, the Clay-colored thrush in Central America, and the Amery-can robin in North America.
Many of the true thrushes are noted frothier songs, which characteristically are composed of a succession of short, richly warbled, or fluty phrases a few species are remarkable mimics. Their substantial cup nests are strengthened by a layer of mud, often mixed with decaying leaves, and are usually finished with an inner lining of grasses or similar material. Northern species are long-distance migrants, and tropical speciesnonmigratory, while some species from middle latitudes are partial migrants, some individuals moving south in winter and some remaining in their breeding area.
The ground thrushes are closely related to the true thrushes. They have the same general build but relatively longer, stouter bills. And are further distinguished by striking, usually black and white, under-wing patterns. They are shy birds, living near the ground in forests, and are mainly confined to Asia and Africa. The only exceptions are the widespread White’s thrush whose breeding range extends, uniquely in the sub-family, to Australia, the Varied thrush of western North America, and the Aztec thrush of Mexico.
The large group of robins, robin-chats, and related species (including the nightingale) are small thrushes of woodland and tropical forest, mainly ground feeders and with proportionately longer legs than the true thrushes. A few, such as the alethesof tropical Africa, are habitual followers of army ants, feeding on insects flushed by the ants. Some have remarkably fine songs. Another group of small thrushes—chats, wheatears, and their allies –inhabit the more open country, nesting in holes or recesses in the ground; among these, the desert wheatears inhabit country as barren as any in which a bird can survive.
These two groups of small thrushes have their headquarters in Asia and Africa. They are, entirely unrepresented in the New World. Where—apart from many species of true thrushes—the subfamily is represented by a much smaller variety of forms. Most outstanding of which are the Hermit thrush and its relatives in North America. Bluebirds, nightingale thrushes, and solitaires.
Some of these, including the Hermit thrush and solitaires, are among the world’s finest songsters, noted for their pure and exquisitely modulated notes. It seems certain that the main evolutionary radiation of the thrushes took place in East Asia, and it is there that the subfamily is present in the greatest variety. The whistling thrushes, which include the largest of all thrushes, live along fast-flowing streams in the Himalayas and other mountains of eastern Asia.
They have strongly hooked bills and forage for animal food among rocks at the water’s edge. The forktails, slender birds with long tails, and the water redstarts are also specialists in foraging along the banks of mountain torrents. The grandala, a long-winged and short-legged bird with blue plumage, is so unlike a typical thrush that its inclusion in the subfamily is at first sight surprising.
Grand alas is a highly aerial, social bird that lives above the timberline in the Himalayas and associated mountains, where they feed in flocks on bare mountain slopes. Almost equally unthrushlike are the three species of cocoas. They are wide-billed birds of tropical forests in Southeast Asia. With plumage patterned with green, blue, and violet. Though little known, they are probably eco-logical equivalents of the coatings of tropical America.
Babblers form a varied assemblage of small to medium-sized songbirds which are an important constituent of the bird populations of tropical Asia. In the middle altitudes of the Himalayas (1,500-3,000m, 5, 000—o, 000ft) they are the dominant passerines, with 71 species breeding in Nepal alone, out of a resident passerine community of about species.
Behavior and feeding ecology within the family are very diverse, with some species of active leaf-gleaners flitting in the forest canopy like warblers and other, robust, heavy-bodied genera rooting like thrushes among leaf litter on the forest floor. The “average” babbler falls between a spar-row and a thrush in size, with short, rounded wings and a longish, rather floppy, tail. They forage in bushes, low vegetation, and on the ground.
In Africa, the family is represented mainly by the chatterers, which are birds of scrubland savanna. In North Africa, the Middle East, and Iran the Fulvous and Arabian babblers and their allies live in sparsely vegetated wades in the open deserts. In the Negev Desert of Israel, the Arabian babbler is the commonest resident bird, occurring wherever there are a few acacias hushes to provide cover and nest sites. In contrast, the Iraq babbler inhabits the extensive swamps of the Tigris-Euphrates delta.
At the other extreme of the habitat scale, a great diversity of different babblers inhabits the cloud forests of the eastern Himalayas, from tiny wren babblers that skulk in among rotting logs on the forest floor to the large scimitar babblers, probing with their hoopoe-like bills, and Black-cappedsibia, drinking the sap oozing from holes in the trunks of oak trees, after the fashion of North American sapsuckers. Geographically close, but far off in terms of ecology the babies inhabit the buckthorn scrub on the southern edge of the Tibetan plateau, in an arid high-altitude desert.
In India the Common and Jungle babblers are among the most familiar birds of garden and roadside, moving in noisy bands from tree to tree and sometimes, especially in the early morning, hopping about on tarmac roads. Parties of 5— r 5 birds are the rule and these normally consist of extended families, with the whole group collaborating to incubate the eggs laid by the dominant female (and presumably fertilized by the dominant male). All members assist in feed-in the nestlings, but despite this assistance, the young birds grow no faster than other passerines, fledging in about 14 days.
Groups of jungle babblers defend collective territories: encounters between neighboring groups are very noisy, with most of the birds on each side calling excitedly. Fighting sometimes breaks out in these skirmishes and antagonists can he see rolling on the ground with their claws locked together, oblivious of the human observer?
The behavior of the more brightly colored laughing thrushes is similar to that of the jungle babbler, but they often occur in enlarger groups of up to r 00 birds. In the even-in these break up into small parties of 2-1birds which roost separately but within a fairly small area, recombining the next morning. The spectacular White-crested laughing thrush performs a remarkable communal display in which several members take part.
Prancing together on the forest floor, their white crests raised like helmets, uttering a series of laughing calls that gradually mount to a crescendo. At dawn and dusk, these calls are normally answered by neighboring groups, producing a chorus of choruses that echo among the densely forested hills which they inhabit.
In the evergreen rain forests of Southeast Asia and the temperate forests of the Himalayas babblers are important members of the associations of several species of small insect-eating birds that join together for foraging expeditions: a striking feature of the area’s bird life. Those involved include inlays. Yuhinas. Tree babblers, tit-babblers, and shrike-babblers. Which mix freely with warblers? Tits, minutes, tree creepers, and woodpeckers form loosely organized parties, sometimes numbering several hundred, moving steadily through the forest throughout the day and only breaking in the evening to roost in separate single-species groups.
See more: Warblers