Sociable weavers – the noisy thatchers
You know you’re in the Kalahari when you start seeing huge, thatched nests attached to any likely vertical structure – quiver trees, telephone poles, wind pumps and camelthorns.
These are the homes of sociable weavers, and they are the largest bird-made structures in the world. Why? Because these birds simply don’t know when to stop.
Up to 300 birds will live in such a structure, and every day, each bird will bring back grass stalks to add to the nest.
They’re a bit like Pixar cartoon birds on speed. They hardly ever rest, except to have a power nap in the heat of a summer’s day. Even if you pass a sociable weaver nest in the starry dark of a summer’s night, you’ll hear their restless nattering and fluttering.
No matter how sturdy the tree or pole, eventually it collapses under the weight of tons of grass. Undaunted, these nondescript, relentless and ever-twittering little birds just start again.
They’re a bit like Pixar cartoon birds on speed. They hardly ever rest, except to have a power nap in the heat of a summer’s day.
These funny little birds with their bluish beaks are also impressively altruistic.
In Trevor Carnaby’s fat book on bird behaviour (Beat About the Bush: Birds), he points out that sociable weavers actually help each other raise broods, and repair nesting chambers for one another.
The grass is wonderfully insulating, making for cosy conditions in winter and relatively cool conditions in summer. As a result, the food needs of these little birds are dramatically reduced.
I’ve never seen the beginnings of a nest, but Carnaby says that a few pairs of sociable weavers begin one by creating a latticework of twigs along a branch. Then grass stalks are wedged into the framework. Eventually, they are able to fashion individual little chambers, each with a cunning little ridge to hold onto and to stop any eggs from rolling out.
Each nest is a masterpiece of bird engineering.
Telephone technicians try to discourage nest-building among crucial components at the top of poles by providing wire ‘starting structures’ lower down on the poles. It’s mostly in vain.
All that shelter does not go unnoticed. Pygmy falcons have a longstanding relationship with sociable weavers, and rely entirely on these little birds and their construction talents for their own housing requirements.
In return for benefiting from a sheltered apartment, centrally heated by weaver power, they (mostly) refrain from eating chicks.
And if that wasn’t enough, owls, geese and other creatures sometimes nest on top of sociable weaver nests, adding their own bit of weight to the tipping point that precedes collapse...