CONCLUSION
We performed a genome wide association study to investigate which genes may underlie differences between red and yellow feathers in tinkerbirds. We found an association with CYP2J19 on chromosome 8, to our knowledge this is the first time such an association has been found with feather colour across a natural avian hybrid zone, indeed the first timeCYP2J19 has been associated with red feather colour in a nonpasserine bird. Asymmetric hybridisation suggests a preference for red plumage in females that share the red trait, consistent with converted carotenoids reflecting male fitness.