The development of the feathers and the feather follicles is extremely involved and a complex part of the bird, writes Doug Ottinger. Animal health pros may find his article worth reading if feather development is not a familiar topic.
The feather is a complex epidermal organ.”
Source: Backyard Poultry, October 5, 2022. Link. The follicles, feathers, and skin of the chicken, as well as other birds, start forming during the first few days of embryonic growth. Complex chemical interactions, all dictated by the genes in the newly forming cells, take place in these regions, giving rise to what will become the feathers, in all of their shapes, colors and individual purposes in the life of the bird.
Image credit: MyPetChicken