The Sociable Weaver has a highly gregarious nature. It's breeding habits are colonial, co-operative and not entirely monogamous. Colonies of up to 500 birds build and maintain enormous structures in trees, on telephone poles, on windmills and sometimes on rockfaces or under bridges.
While travelling through the Northern Cape on our way to Namibia last week, we passed literally hundreds of these nests built on telephone poles. I photographed one such structure which I posted on Skywatch Friday under yesterday's date.
These nests are built almost entirely of grass and each pair builds it's own nest chamber within the structure, used either for roosting or breeding.
Normally a Pygmy Falcon takes up residence and breeds in this structure as well. The Sociable Weavers benefit from this unofficial guest, as these little raptors eat any snakes or reptiles which may try to gain entry into the nests. The Pygmy Falcons have been known to snack on the odd Sociable Weaver nestling but this is the exception rather than the rule.
It was rather fascinating to me that these nests were visible on almost every second or third telephone pole along the highway to Namibia. However, the minute we passed through the border posts and were on our way across the Namibian countryside, there were no more Sociable Weavers nests. I chuckled to myself thinking perhaps they didn't have passports! Further north though, the nests made their very obvious appearance again and petered out once we crossed the border into Botswana.
Having lived on the West Coast of Southern Africa (now Namibia) and having travelled regularly through this remarkable bird's habitat, I am familiar with this species and it's nests. However, the Sociable Weaver and their engineering feats never cease to amaze me.