Tag Archives: Philetairus socius

Bird of the Week – Week 119 – Sociable weaver

Sociable weavers are small birds with a length of about 14 cm and the sexes are alike in both size and plumage colouration. Their upper parts are scalloped with black and their under parts are white; their flanks are marked with black; and they have black face masks. Bills are grey; eyes are brown; legs and feet dark grey.

Sociable weaver

Pretty little birds, yes, but the most distinctive feature of Sociable weavers is not the birds themselves, but rather their enormous communal nests. The nests, which may house up to 500 birds, can be seen on trees, telephone poles, windmills or virtually any structure within the arid savannah which is their preferred habitat. The nests, made entirely from grass and some thought to be decades old, can become so heavy that the branches to which they are attached snap under the load and it is not unusual to see these nests on the ground.

Sociable weaver

These enormous nests, probably amongst the largest structures made by any birds, are often subject to predation, particularly by Cape cobras that feed on the eggs and young nestlings, an event that we were excited to witness at a large nest in eastern Namibia. Some of the chambers within the nests are sometimes taken over by Pygmy falcons (Polihierax semitorquatus), Rosy-faced lovebirds (Agapornis roseicollis) and other species for roosting or breeding. The nests may catch fire during the summer months and the nests that are built on electricity pylons may cause short circuits when they become wet during periods of rain.

Sociable weaver

Each pair of birds builds its own chamber within these communal nests, in which the female lays a clutch of between two and six eggs that hatch after an incubation of about 14 days.

Sociable weavers are endemic to the southern African region, their distribution being limited to the arid north-western parts of South Africa and a large part of southern and central Namibia. Sociable weavers are mainly insectivorous, although they eat some seeds, and they do most of their foraging on the ground.

Sociable weaver

Their call is a series of metallic chipping sounds.

The scientific binomial for the Sociable weaver is Philetairus socius; Philetairus from the Latin for “loving friends and companions”, and socius from the Latin for “sociable”. Thus we have an extremely sociable bird, twice over!

Sociable weaver

Cape cobra raiding a Sociable weavers nest

The huge nests of the Sociable weaver (Philetairus socius) are quite common throughout the drier woodland and savanna of Namibia, clinging to trees and pylons like so many haystacks.  Any literature on these colonially nesting little birds is likely to mention that the nests are frequently raided by predators such as honey badgers and snakes, and the Cape cobra (Naja nivea) will often get a particular mention.

For this reason we usually look quite carefully at these magnificent structures while out in the veld, and quite recently while driving along a relatively deserted gravel road in the Kalahari, our persistence was rewarded when we saw a golden loop suspended from the underside of a medium sized nest.  A Cape cobra, its head buried in one nesting chamber and its tail in another.

Cape cobra at sociable weaver nest

We positioned ourselves below the nest, which was about three metres above the ground in a large Camel thorn tree (Acacia erioloba) and waited.  Many of the Sociable weavers flitted to-and-fro, arriving at the nest with insects tightly clasped in their bills and perching nearby, uttering rather sad little chirps as they looked on.  Watching the body of the snake we could clearly see bulges moving down its length as it swallowed the young birds that it found in the nest.  (As the adult birds were bringing food to the nest, we assumed that these were young birds being devoured rather than eggs.)

Cape cobra at sociable weaver nest

After a few minutes the snake withdrew its head and upper body from the nesting chamber in which it had been feeding, presumably having exhausted the food supply there, and moved quite cautiously to an adjacent chamber.  As it was on the underside of the nest, it kept itself firmly anchored in one of the chambers with its lower body as it moved, its head and upper-body suspended below the nest without support.

Cape cobra at sociable weaver nest

We were surprised that the little weavers made no attempt to mob the snake and although they were clearly agitated by its presence, they kept their distance and looked on.  It was quite sad to see the birds returning with food for the chicks, that had themselves become food during the interim – for the cobra.  The nest was obviously home to many young birds, and some of the adults entered chambers quite close to those being visited by the cobra, to feed chicks that had survived thus far.  We wondered how long it would be before the cobra made its way to those chambers….

Sociable weaver at nest

After we had been watching the snake for the best part of an hour, during much of which very little of its body was visible, it withdrew completely into one of the chambers and didn’t emerge for the next ten minutes.  Perhaps it was sated for the moment and had withdrawn to rest.

Cape cobra at sociable weaver nest_0

We realized that many of the nests that we had seen over the years were probably being raided by snakes even as we looked on, because the presence of snakes is really quite difficult to see unless you happen to be passing just when they are moving from one chamber to the other.  While they are busy feeding or resting, they are, to the casual observer, practically invisible.  As so often happens with events in the bushveld, it is all a matter of timing!  And the moral of the story – be careful about putting your hands in nests.

Cape cobra at sociable weaver nest

Sociable weaver’s nests – Nature’s condominiums!

On our first trip from South Africa to Namibia, we drove through the dry region of the Northern Cape and it was there that I first came across the fascinating nests of the Sociable weaver (Philetairus socius). They had taken up residence on virtually every telephone pole in sight and their bulky nests laid claim to their space along the highway. It was a foretaste of what was to come in Namibia and the Kalahari, where these enormous nests are the order of the day. They are nature’s version of the condominium – complete with their own air-conditioning system!

Sociable weavers nests

Sociable weaver’s nests are the biggest nests built by any bird and a single nest can accommodate up to three hundred birds, including their chicks.

Nature's condominium

The nest consists of several chambers, each built by a breeding pair, and it is not uncommon to see the birds busily flying to and from the nests with bits of grass in their beaks adding even more to what looks like a haystack in a tree or on a pole. Often the nest gets so heavy that the branch breaks, sending it tumbling to the ground.

Chamber entrances

Although it looks like new chambers are randomly added on, the nests are cleverly structured to provide different areas for shelter and roosting. The inner chambers are well insulated, being warmer, and are used for nighttime roosting, whilst the outer ones are used for shade during the day and are much cooler. When outside temperatures rise to uncomfortable levels, the outer chambers can maintain temperatures as low as 7oC.

A typical nest

The nests face a number of dangers. They can catch fire in summer and, if built on electricity poles, can cause short circuits in rainy weather. Their main predators in trees are Cape Cobras, which have a voracious appetite for the eggs and chicks. Whenever we’re in the Kgalagadi Transfrontier Park, we always stop and look out for cobras on these nests – so far we haven’t seen any! Lizards, insects and honey badgers are also a threat to Sociable weavers. The Pygmy falcon, which cannot survive harsh variations in temperature, uses the weaver’s nest and assists with guarding it from predators.

Sociable weaver

I love the different shapes and sizes of these nests and am always on the lookout for them when we are traveling through the countryside.