Is evolution predictable? Theoretical modelling provides revolutionary insight into, allowing predictions on the evolutionary path of a species. Hybridization, the process of interbreeding between two distinct species, has the potential to significantly impact this path, however it is frequently excluded from speciation models. This Keystone examines the unique hybrid mating patterns found in Ficedula Flycatchers, to explore and adapt a theoretical model to predict hybridization probability and frequency between two interbreeding populations. A better understanding of hybridization frequency is beneficial to understanding both biological factors incentivizing heterospecific mating, and the predictive capability for the evolutionary fate of a species.