The weaver group is divided into the buffalo, sparrow, typical, and widow weavers. The African buffalo weavers are black-and-brown birds 8 to 10 in. (20.3-25.4 cm) long, that travel in small flocks and build bulky compartmented nests with separate chambers for two or more pairs. Of the 35 sparrow weavers the best known, and in fact one of the most widely distributed and familiar small birds in the world, is the English sparrow native to Europe, W Asia, and N Africa. It is the most successful town and city dweller among birds, and has followed European civilization wherever it has gone; it was introduced to North America in 1852.
As common in Asia is the Eurasian tree sparrow (also introduced in the United States), a nuisance in rice fields and sold in great quantities for food. These birds build untidy domed nests with side entrances. Most specialized of the sparrow weavers is the social weaver of Africa, famous for its apartment-house nest, in which 100 to 300 pairs have separate flask-shaped chambers entered by tubes at the bottom. They build these structures, which may be 10 ft (3 m) high and 15 ft (4.5 m) across, high in a sturdy tree, beginning with a roof of straw thatch.
Of the 100 or more African and Asian typical weavers, the small quelea, only 5 in. (12.7 cm) long, sometimes causes huge crop losses in Africa by feeding on grain in flocks numbering as many as one million birds. The African widow weavers (named for the long, drooping black tail plumes of the breeding male), or whydahs, are notable for their selective parasitic nesting habits; they lay their eggs in the nests of waxbills, and their eggs are white, as are those of the waxbill, rather than spotted, as are those of all other weavers.
Many of the weaver family are kept as cage birds, especially the colorful waxbills (e.g., the Java sparrow, mannikin, munia, grenadier, cutthroat, and cordon-bleu, locust, parrot, Gouldian, and fire finches). Weaverbirds are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Passeriformes.