In the Kalahari, giant straw masterpieces offer separate apartments, but watch out for snakes
That heap of hay in a tree is not a typical animal commune. Huge group nests of sociable weaver birds across southern Africa are about as close as nature gets to building condos.
Ant nests, beaver lodges and many other marvels of animal architecture enclose shared space. But small, sparrowlike Philetairus socius push together beakful after beakful of grass to create a haystack of apartments. The nests can grow to weigh a ton and last about a century. Tunnels opening from the shaggy underside lead to each family’s unit. For better and worse, a weaver bird nest “in practice is like a block of flats,” says evolutionary biologist Rita Covas of CIBIO Research Center at the University of Portugal.
The condos have great insulation, an important perk for birds that don’t migrate from the hot-then-cold Kalahari. In summer, Covas can feel shady relief when she reaches up into a nest. In winter, condos are heated by snuggle power. The thatch keeps a