In Kenya, pygmy falcons nest in white-headed buffalo weaver nests, and the ranges of the two birds coincide.
 In southern Africa, they are found around red-billed buffalo weaver nests but predominantly nest in the vacant rooms of sociable weaver nests, which are large and multichambered—even if the sociable weavers still have an active colony in the nest.
Despite being bird-eaters and bigger than sociable weavers, the pygmy falcons largely leave the latter alone, though they do occasionally catch and eat nestlings and even adults.

Pygmy falcons provided one of the rare documented cases of intraspecific killing to acquire a new mate and territory.
In Kenya, pygmy falcons nest in white-headed buffalo weaver nests, and the ranges of the two birds coincide.  In southern Africa, they are found around red-billed buffalo weaver nests but predominantly nest in the vacant rooms of sociable weaver nests, which are large and multichambered—even if the sociable weavers still have an active colony in the nest. Despite being bird-eaters and bigger than sociable weavers, the pygmy falcons largely leave the latter alone, though they do occasionally catch and eat nestlings and even adults.
Pygmy falcons provided one of the rare documented cases of intraspecific killing to acquire a new mate and territory.
Pygmy falcon