Our paper “Coevolution and the diversification of nestling ornamentation in a species-rich avian radiation” has now been published in the journal Evolution. This paper, led by Gabriel Jamie, explores the diversification of nestling ornamentation across the estrildid finches (family Estrildidae), a species rich group of birds with unparalleled diversity in nestling ornamentation. Many are hosts to brood-parasitic Vidua finches whose offspring mimic host nestling phenotypes. The paper examines the role of brood parasitism, predation, sibling competition, and signaling environment in the diversification of nestling ornamentation. The paper finds that parasitised lineages of estrildid finches show faster rates of nestling ornamentation evolution than unparasitised ones. Despite this, parasitised lineages were not found to be more ornamented than unparasitised ones. This suggests parasite mimicry selects for host offspring to evolve away from parasite phenotypes but not necessarily in a direction of elevated ornamentation. Additionally, species occupying denser habitats had increased ornamentation. Overall our results support a role for both species interactions and interactions with the abiotic environment in driving the evolution of nestling ornamentation.They also suggest that, in this system, hosts rather than parasites lead the way in the co-evolutionary arms race. You can read the full paper here.