While driving through the long and dusty stretches of Namibia, travellers may see huge bird nests crafted onto convenient telephone and electricity poles. Most hardly slow the pace of their hire cars to wonder at this strange phenomenon of nature caused by sociable weavers. It also is fairly common in Botswana and the Northern Cape Province of South Africa too.
All This Effort by Such a Tiny Bird
The sociable weaver, or philetairus socius if you like things formal, is a scanty 14 cm long, and tips the scales at 25 to 32 grams. Despite being somewhat plain with black banded flanks, black chins, and scalloped backs, they enter the record books when it comes to their huge nests woven from stiff, indigenous grasses.
Their sexes are indistinguishable and they breed at any time of the year subject to there being rainfall. It is just as well that they are sociable weavers. They may raise four broods under the right conditions, when close and distant family members pitch in and help. However, they may remain celibate for years when drought strikes the fiercely hot and arid region.
The Huge Nests of Sociable Weavers
There is no maximum design size. Sociable weavers keep on building until the nest collapses. Some nests may last a century, and be handed down to countless thousands of birds in a remarkably natural bequest. Ripley’s thinks the nests may accommodate up to 300 birds at a time, and that’s a lot of twittering. Trust me the chattering can be deafening.
The nests function as climate control centres. The inner rooms are for keeping warm at night for breeding. The outer rooms are ‘shade porches’ maintaining temperatures at 7 to 8 Celsius compares to up to 33 outside. The birds place sharp sticks at entrances to their nests in the oft-vain hope of deterring snakes from entering and consuming all their eggs at a single sitting.
Coexistence with Human Settlement
Sociable weavers often build their nests on telephone poles and electricity pylons whose intricate structure makes them easy to attach. These sometimes cause electric short circuits when it rains, causing the nests to burn, and the grid to trip. Notwithstanding this, the population of social weavers is increasing. Although I very much doubt the utilities regard this as cause for celebration.