Diverge or merge?: The effect of sympatric occurrence on the territorial vocalizations of the vinaceous dove Streptopelia vinacea and the ring-necked dove S. capicola

Sympatric occurrence of two closely related species is expected to lead to diverging or converging shifts in signal characteristics of one or both species. We examined signal characteristics in the vinaceous dove Streptopelia vinacea and the ring-necked dove S. capicola, two sister species that are mainly allopatric but occur in sympatry in northwestern Uganda. Vocal characteristics of the birds in sympatry were compared with those of an adjacent and a distant allopatric population of each species. The sympatric population showed intermediate values between the allopatric populations from Uganda. However, within each species there is little geographic variation between distant allopatric populations. Since vocal differences between dove species have a genetic base, the convergence in vocal characteristics is most likely explained by hybridization. Probably, the two species came into secondary contact relatively recently. Climatic changes during the last several thousand years and recent habitat changes caused by the growing human population, may have allowed Streptopelia capicola to extend its range in the northern direction.