One of the most remarkable creatures of the Kalahari Desert is the sparrowlike weaverbird. Small, gray creatures, they are unremarkable unless they have gathered in a group, when they become one of the planet's most interesting and sociable birds. Hundreds of birds form a single flock, which then cooperatively weaves a giant nest of twigs that can all but absorb an acacia tree, especially the viciously barbed camelthorn tree. These acacia trees provide one of the few refuges for birds in the heart of the Kalahari, since the trees can withstand 0 months without a drop of rain. The nests can measure six feet (1.83 m) or more across and provide refuge for hundreds of birds.
By some calculation known only to weaverbirds, they allocate annual nesting rights. Some percentage of the females lay eggs while the other, nonbreeding members of the colony cooperate to feed the nesting parents and their offspring.