Sociable Weavers

Abstract

In nature the Sociable Weaver is restricted to arid and semi-arid southwestern Africa where the annual rainfall ranges from about 3 to 24 inches a year (Maclean, 1973). In the Kalahari Desert the temperature may range from 33°C (91.4°F) in summer down to -10°C (14°F) in winter (White, et al., 1975).

The species is noted for its giant communal nest, probably the most spectacular nest built by any bird. These nest masses, which may reach over 25 feet across, are usually placed in large acacia trees, and are built of dry straws, grass tops and fine twigs. The nest has often been likened in general appearance to "a haystack in a tree." Despite the large size of their nest, the birds themselves are smaller than a House Sparrow (Passer domesticus] which they superficially resemble. The species belongs to the weaverbird family (Ploceidae).

The immense compound nest is built by a group of birds, and the underside of a nest mass may contain 50 or more individual nest chambers opening downwards. The birds build on their nest and inhabit it the year around. Each pair, or family, defends its own chamber, but any of the birds may build on the communal roof. Details of nest structure and construction are given elsewhere (Collias and Collias, 1964, Maclean, 1973).

In nature, the birds breed after periods of rainfall, which are very erratic, and they may continue to breed long after the rains have ceased. The reproductive biology has been described in detail by Maclean (ibid). To the best of our knowledge no one has previously reared this species in captivity. Maclean (1967) tried to rear them in the Kalahari in their native habitat, and got them to hatch eggs but not to fledge.

In August, 1972, we received ten Sociable Weavers from the Kalahari Desert. We kept them in an indoor aviary for about two months. During most of the three years from the autumn of 1972 to the autumn of 1975, we kept the birds in a large outdoor aviary (16 ft. wide, 30 ft. long, and 16 ft. high) at the University of California at Los Angeles. In Los Angeles the annual rainfall averages about 16.5 inches, and the temperature in the aviary ranged from a maximum of 41 °c (106°F) to a minimum of 0°C (32°F) during these three years. The aviary was furnished with a framework of 2 x 4 wooden beams, which supported four boughs on one of which, Darya/us kaffir from South African, the ten birds almost immediately began to build a nest with straws, after being released into the aviary. This particular bough was almost 8 feet long and about 5 to 6 inches in diameter at its large end, and it had many side branches (Fig. 1 ). The birds were provided with nest materials consisting of dry straws and grass tops of various local grasses, especially of wild oats (Avena fatua). In general, they preferred dry, brown grasses with feather tops, a favorite being Smilo Grass (Oryzopsis mileacea). We also have them fine twigs which they added mainly to the roof of the developing structure.

Each bird was given two color bands on each leg in individually distinctive combinations, the same color combinations being used on both legs. The birds were fed on commercially available wild finch seed mixture (yellow, red and white millet, canary seed, niger, rape and flax) and canary seed mixture (canary seed, rape, and saffron), mealworms, and later on crickets as well. They were also provided with cuttlebone, crushed egg shell and a pan of drinking water in which we sometimes put vitamins (Avitron). After the young fledged we shifted to Vionate as a vitamin source.

The sexes are identical in appearance, and previous behavioral studies have been limited by the fact that the sex of the birds was unknown. We discovered that the male of this species has a distinctive song, and that the female does not sing. We found it very helpful in understanding the behavior of the birds to be able to distinguish the sexes. In spite of the sociable reputation of this species we found that some of the individuals were very aggressive, and we lost some birds as a result of intraspecific strife.

During the first few months in the aviary the birds were engaged in building their nest mass, and no eggs were laid until after the first four nest chambers had been built. The first eggs were laid in the middle of January, 1973. Four females paired with males and three of them laid eggs in separate chambers. The fourth pair was removed before they laid eggs because they were so aggressive they were...