05-07-2025
Sparrow-weaver nests help shape bird biodiversity in the southern Kalahari
Photo by Lesedi Moagi
Conducting fieldwork under the blistering 40°C heat of the southern Kalahari,
'Some mornings, by 7.30am, it was already over 20°C,' recalled Moagi, a master's student at the University of Cape Town. 'And the birds were already becoming less active. They have to split their daily activities depending on the temperature.'
Moagi's research focused on understanding how the
'We already knew that birds like scaly-feathered weavers, ashy tits and the Acacia pied barbet were roosting in these nests,' she said, noting this behaviour hadn't been studied in detail.
The inspiration for the research came from another desert species — the sociable weaver — whose apartment-block-like communal nests are used by a variety of species. That research is well-established, Moagi said.
'With white-browed sparrow-weavers, their nests are also being used by other bird species but this has not been studied deeply and it hasn't been understood as well. That's how the idea came about — that it would be cool to actually try to understand the value that these nests hold in the ecosystem.'
(Photo by Azraa Ebrahim)
To assess the effect of the sparrow-weaver's nest structures, she observed both naturally occurring nests and those that had fallen in the wind, which she relocated to trees without nests. She then compared bird abundance and species diversity in areas with and without nests.
'We wanted to see if they also affect the overall avian community in the Kalahari to see in an area with more of these nests,' she said. 'We wanted to measure the avian abundance and the number of species that are actually hanging around these nests. We saw their numbers increasing.'
Her findings position the sparrow-weavers as ecosystem engineers — species that modify the environment in ways that benefit other organisms. But the sparrow-weaver population itself may be under threat.
Once common across the Kalahari,
Moagi said fewer sparrow-weavers could mean fewer shelters, which might force other species to expend more energy building their own, or even struggle to survive.
'The physical changes the sparrow-weavers make influence the distribution of the animals. If we have less of these sparrow-weavers, it might affect the number of the species that are using these structures; it might influence their distribution and their movement.'
(Photo by Sthabile Khumalo)
The ability to find safe, insulated shelter is critical for survival in the harsh Kalahari environment. 'The Kalahari is so hot. Birds can't finish building a nest in a single day because it gets so hot and they need to conserve their energy.'
Moagi also placed temperature loggers inside and outside the nests to measure their insulation. The results showed that the nests provided a consistent buffer against extreme temperatures — up to a 4°C difference compared to the surrounding air.
In the Kalahari, that kind of thermal stability is crucial.
With
She suggested practical interventions including providing water points and shaded areas in key nesting zones and preserving grasses used in nest-building.
