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 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.
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.
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.
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.
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.