Juvenile plumage whiteness is associated with the evolution of clutch size in passerines

The offspring of many animals are conspicuous during parental dependence, despite juveniles generally suffering from high predation risk. However, to date, it is unclear whether offspring structural ornaments play a role in intra-family communication. This is the case of conspicuous plumage in young birds, which is worn unchanged during a long period after fledging, when they still depend on their parents. If plumage color facilitates intra-family interactions, its role should be more important in large-brooded species, where the strength of intra-family conflict is potentially stronger. We therefore performed a comparative study in 210 passerine bird species to test whether an offspring structural trait, white plumage, evolves more frequently in lineages with larger clutches. We also explored the number of broods raised per year as another source of intra-family conflict. First, we found that juvenile whiteness was more frequent in open-nesting species. Moreover, in agreement with our ...