Colours of Wildlife: The Sociable Weaver
Created | Updated May 18, 2014
Sociable Weaver
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
After last time's spectacular owl, I bring you a small and humble little bird, a Sociable Weaver, Philetairus socius. This drab little bird is not much to look at: it's the same size as a house sparrow, and has dull brownish plumage, only elaborated by a small black face mask, and a black-and-white scale pattern on its back and wings. It also has a few unusual scaly feathers on its sides, that look much like the coverts on its wings. But apart from that, it has no particularly distinguishing features. Sociable weavers live in dry semi-desert regions of South Africa, Botswana and Namibia. They feed on seeds and insects like harvester termites which they mostly pick up from the ground.
Haystacks in the Trees
"Surely", you think, "there must be more to this little bird, or why would Willem waste our time with so many more words in this article?" Well I'm glad you thought that. It seems to me to be the case that nothing that exists is 'merely' anything at all … there's always something special and interesting about it. In the case of this little weaver, the interesting thing is not difficult to find. If you direct your gaze at my illustration, you might see behind the bird, toward the right upper region of the image, a strange thing. No, this is not the amazing Namibian haystack tree, this is actually the nest of the Sociable Weaver in an old, dead camel thorn tree. Actually, not of one weaver – it is the nest of dozens of them!
Sociable weaver nests are indeed some of the most amazing structures built by any living creature. Some are small – they all start out small of course, the labours of a few individuals. Although this bird is called a weaver, it doesn't really weave as such. It constructs the nest from stiff dry grass stems, starting by laying down the grass on top of the chosen base. As new bits of grass are added they naturally intertwine, interlock and clump together; the weavers don't deliberately twine and knot them together like the true weavers do. But the sociable weaver nests are sturdy enough. The building is done by the male weaver, who picks out suitable stems of grass and carries them one by one to the nest, shoving them into the mass until they're wedged in tightly. The wad of grass is soon large enough to overlap the base, and then the weavers start constructing their resting and nesting chambers in the bottom. The chambers are retort-shaped, with a lip at the edge where the chamber joins the access tunnel, so that chicks or eggs won't fall out.
The communal nest is a well-engineered structure of great benefit to the birds. The large mass of the grass on the top absorbs the intense rays of the sun so that the chambers at the bottom remain cool. On the hottest days, the weavers will retreat to the nest and take a mid-day siesta. But because of grass's insulating properties, the heat absorbed during the day warms the weavers in the cold desert nights. On the coldest nights, the weavers will huddle together, several in one chamber. It has been determined that the inside of an occupied sociable weaver nest chamber, on a sub-freezing winter night, can be 17 to 23 degrees Celsius/30 to 40 degrees Fahrenheit above the outside temperature.
The nests grow and the weavers multiply. If the supporting tree is big and strong enough, the nests can grow into the largest nesting structures in the bird world, reaching seven meters/23 ft in diameter! At this stage the colony might be a hundred years or more old, and in use by almost as many generations of weavers, the present generation numbering two hundred individuals or more. In old nests there are multiple levels of chambers, the older ones being higher up/deeper into the nest structure. It really is like a giant bird apartment complex! It is the kind of nest that can only exist in dry desert or semi-desert climates, since in a moister climate the grass would eventually start decomposing and the nest will become not so much a haystack as a mouldy compost heap.
These nests are extremely conspicuous, so the weavers don't resort to the tricks of other weavers such as removing eggshells and droppings from below the sites. They do have some tricks such as putting sharp or thorny twigs at the top of the nests, and lots of sharp-tipped grass stems sticking straight out around the mouths of the entrance holes at the bottom of the nest. The openings being right at the bottom also make it difficult for many predators to enter. The greatest threats to the weavers are snakes like the boomslang and the Cape cobra, and honey badgers, which can climb into the nest trees and use their strength and claws to tear into the nests, being so tough that the thorns and sharp grasses don't discomfit them. But then the weavers find strength in numbers: if the colony is large enough, the predator can eat its fill and there would still be many nests and chicks that survive. Also, because the nests allow them to stay warm, they are able to breed – if enough food is available – in the cold of winter when the snakes are inactive.
Falcons and Lovebirds
One predatory bird is able to get in under the weaver birds' defences. This is the pygmy falcon. This falcon is just slightly larger than a sparrow itself, one of the smallest falcon species in the world. It has almost the same distribution in South Africa as the sociable weaver. These falcons often take up residence in the weaver's 'apartment complexes'. They are tolerated by the weavers and mostly live in peace with them, although they might occasionally take a chick or even an adult bird. But the falcons may benefit the weavers in helping drive away larger predators.
Another bird species that frequently nests in these weaver complexes are lovebirds. These small and endearing parrots, well known as pet birds, occur in the wild in South Africa and Namibia. They, too, are close to the size of the weavers and a pair will sometimes occupy an unused nest chamber.
Yet other birds make use of the sociable weaver nests. Red-headed finches, pied barbets and familiar chats have also been seen using the nest chambers, while barn owls and Giant Eagle Owls often nest on the flat top of the structure.
Humans also have a use for old sociable weaver nests. In Queenswood, Pretoria, the kindergarten my sister and I went to had a large aviary with a huge sociable weaver's nest, kept under a tin canopy to keep it dry, in which many other pet birds were nesting!
Phone lines in peril
Much of Southern Africa still needs regular telephone poles and lines. Trees being rare where the sociable weavers live, telephone poles seem like a natural choice for supporting a nest. Unfortunately the phone lines get messed up by the masses of grass and twigs. Therefore in the regions where these birds occur, telephone technicians have been constructing platforms lower down on the poles so the weavers can build their nests there, away from the wires.
Weavers will also use some other man-made structures as nest supports, such as windmills or water towers. They have an overall wide distribution and human presence is sparse in their natural environment, meaning that at present the species is secure.
