Host specificity of the Pygmy Falcon Polihierax semitorquatus: a review

The Pygmy Falcon Polihierax semitorquatus does not build its own nest but is an obligate user of the nests of colonial birds for roosting and breeding. The nests of various weavers and starlings have been listed, suggesting a wide range of hosts used by the Pygmy Falcon. A search for original references of host use, however, suggests a high degree of host specificity. The two disjunct populations of Pygmy Falcon each specialise on a single weaver host, namely the Sociable Weaver Philetairus socius in the southern population, and the White-headed Buffalo Weaver Dinemellia dinemelli in the eastern population. There are incidental records of roosting or breeding in the nests of the White-browed Sparrow-Weaver Plocepasser mahali and Red-billed Buffalo Weaver Bubalornis niger. No records of Pygmy Falcons using starling nests have been confirmed.