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.
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.)
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.
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….
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.
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.