Delayed feathering in chickens

Delayed-feathering in chickens is a genetically determined delay in the first weeks of feather growing, which occurs normally among the chicks of many chicken breeds and no longer manifests itself once the chicken completes adult plumage. The difference between fast normal feather development and delayed-feathering can be recognized in one-day-old chicks but is always more evident in 10- to 12-day-old chicks.

Source: Wikipedia — Delayed feathering in chickens (CC BY-SA 4.0)