Birds and dinosaurs evolved to dazzle with colourful displays

Iridescence is responsible for some of the most striking visual displays in the animal kingdom. Now, thanks to a new study of feathers from almost 100 modern bird species, scientists have gained new insights into how this colour diversity evolved. Iridescence refers to the phenomena where colour changes when an object is viewed from different angles. Birds produce this varying coloration in their feathers by using nanoscale arrays of melanin-filled organelles (melanosomes) layered with keratin. In this form of structural colouration, the shapes of melanosomes together with the thickness of keratin layers determine what colour is produced. While melanosome morphology has previously been used to predict colour in fossil animals, melanosome variation in iridescent feathers has not been analysed on as large a scale until this study. As reported in the journal Evolution , a team of University of Bristol researchers used scanning electron microscopy to quantify melanosome extracts from the feathers of 97 species of modern birds with iridescent plumage, taken from the collections of the Zoological Museum of Copenhagen.