Our paper “Limits to host colonization and speciation in a radiation of parasitic finches” has just been published in the journal Behavioral Ecology. In this study, led by Dr Gabriel Jamie, we explored the factors which limited the colonisation of new hosts by brood-parasitic Vidua finches. Speciation in these birds is closely connected with the colonisation of new hosts. Therefore, if we can understand what limits this process, we can understand what has limited the diversification of this radiation.
To understand the factors limiting host colonization and, therefore, speciation, we simulated the colonization of a host using cross-fostering experiments in the field. Despite DNA barcoding suggesting that host species feed their chicks similar diets, nestling Vidua had low survival in their new host environment. Nestling Vidua did not alter their begging calls plastically to match those of the new hosts and were fed less compared to both host chicks and to Vidua chicks in their natural host nests. This suggests that a key hurdle in colonizing new hosts is obtaining the right amount rather than the right type of food from host parents. This highlights the importance of mimetic nestling phenotypes in soliciting feeding from foster parents and may explain why successful colonizations tend to be of hosts closely related to the ancestral one.