Sociable weaver nests are a sight to behold, and easily one of the most recognisable structures in the Southern Africa bush.
Unlike other weavers who build their nests in the breeding season, sociable weavers use and maintain the nests throughout the year. They nest in colonies as small as 10 individuals and up to 400-500 birds. Instantly recognisable, their nests can reach phenomenal heights and from a distance can look like a haystack stuck up in a tree or telephone pole.
These community nests are regarded as ecologically important for providing shelter and shade for not only the weavers, but to a large diversity of birds and other fauna.
At Tswalu Kalahari Private Game Reserve in South Africa, it has been observed that a number of fauna have taken advantage of the nest chambers, from paper wasps building their nests under the weaver nests, to birds such as acacia pied barbet, ashy tit, and red-headed finch roosting in the chambers.
Kudu and impala use the weaver nests for shade, while baboons and slender mongoose use them as sites for foraging. Even the wild cats such as leopard and cheetah take advantage of the nests by taking refuge in and use as a platform to gain a good vantage point from which to view the landscape.
Most notably, there is one extreme association that is currently being studied at Tswalu Kalahari and that is the association between sociable weavers and pygmy falcons – particularly since the falcons have been found to frequently prey on weaver chicks.
The study is headed by Dr. Robert Thomson from the Department of Biology at the University of Turku in Finland, who aims to unravel the mysteries behind this unique association and to determine the nature of the interaction between these two species, delving into the demography and life history of the pygmy falcon.
In this situation, it looks like the ‘predator’ (the falcon), not the prey (sociable weavers), makes the active association choice.
However, the true nature of the relationship in this association, be it mutualism (symbiosis which is beneficial to both species), commensalism (where the one benefits and the other derives neither benefit nor harm) or parasitism (a non-mutual relationship where one species, the parasite, benefits at the expense of the other, the host), is unclear, and the system is largely unstudied.
So far it seems that the falcons are particularly fond of the larger weaver nests and while they mostly inhabit colonies as breeding pairs, breeding groups of up to six adults have been recorded.
However, researchers are not convinced these interactions are all negative from the weaver’s perspective. The exact nature of the interaction between the pygmy falcons and sociable weavers is currently under study.