Sociable Weavers

If you take a road trip through the dry parts of our region, you’ll see plenty of giant straw domes on the roadside poles or in big trees. What are these monstrous structures? They are the biggest bird nests in the world, and belong to the Sociable Weaver. But how does a 14 cm bird build such an enormous nest? Through teamwork! Here are some interesting facts about Sociable Weavers’ nests.

Massive nests can measure 7×4 m. That means they will fill up an entire room in your house. And they can weigh more than 1 ton – that’s 1,000 kg.
The nest is the biggest single structure built by any bird in the world. Bigger than even the biggest eagle or stork nest.
Most nests are built in trees, and especially camel thorns. However the birds also like making their nests on telephone poles. Engineers sometimes provide special platforms for the birds to hang their nests from, so that they don’t damage the communications equipment.
Sometimes Sociable Weavers build their nests on cliffs, roofs or windmills or other artificial structures.
In the early stages, a tiny nest can be home to only a single pair of weavers. But over time more and more join in. Big nests can be home to 500 birds!
Each pair builds their own chamber in the bottom of the nest mass, but they all share a roof. The whole thing is called a superstructure.
Each pair’s home within this “apartment block” is about 10-14 cm wide and 8-10 cm high. That’s about the size of a melon. Each pair has their own “driveway” – a tunnel of about 25 cm long that leads upwards.
There are spiky grasses all along the walls of the entrance tunnel. This makes it more difficult for predators to get in.
Nevertheless, there are many nest predators. One of the main ones is Cape Cobras that hang around the nest all the time and eat the babies.
Nests can become more than 100 years old. The main problem is that they get so heavy that they can break the trees that they’re built in.
If the nest falls, the whole colony may be abandoned, even if there are still babies to be fed. But the birds will also recycle, by picking up fallen grasses and repairing the nest.
Sociable Weavers feed mostly within 1.4 km of their nests, but may fly up to 4 km to drink.
Pygmy Falcons use one nest chamber for themselves. If you stand under the nest you can tell which hole belongs to the falcons because of the white ring of dropping around the entrance.
Pygmy Falcons mostly live in peace alongside the weavers, but will sometimes catch one. Because of this, the weavers make alarm calls when they see a falcon approaching.
There is a special kind of lizard, called the Kalahari Tree Skink, that lives in and around Sociable Weaver nests. Pygmy Falcons are one of their main predators. But the skinks have learned to listen for the alarm calls of Sociable Weavers, and quickly run for cover when they are warned of danger approaching.
Other nest squatters include Rosy-faced Lovebirds, Red-headed Finches, Ashy Tits, Familiar Chats and Acacia Pied Barbets. Not to mention various rodents, geckos, insects and parasites.
Most Sociable Weavers stay with their colonies. Less than 5% of youngsters go off to join other colonies.