Evolution of false nests in Estrildidae

Abstract

Some African species within the Estrilda and Amandava genera of Estrildidae build a “cock’s nest,” or false nest, on the top of their nest structure. This false nest’s function is currently unknown; however, it is thought to be a mechanism used to prevent brood-parasitism by whydahs and indigobirds (Viduidae). There may be an evolutionary relationship between the hosts and their parasites in the selection of these unique structures. Utilizing online databases, I was able to construct a list of all species within Estrildidae which create these false nests and create two phylogenies for each family (Estrildidae and Viduidae). I found that nine species of Estrildidae create these false nests, and six of them are targeted by one brood-parasite, Vidua macroura, which also appears to prefer spherical, domed, grounded nests. These results suggest that the false nests may have evolved as an adaptation against nest predation by Vidua macroura, specifically.