Meet the Transylvanian naked neck chicken – you can understand how it got its name, and why it used to be called a “turken”. This unusual bird isn’t part-turkey; it’s a genuine chicken, albeit one with an unusual lack of feathers on its neck and sparser plumes on its body. Now, Chunyan Mou from the University of Edinburgh has discovered the single genetic tweak behind the chicken’s unusual appearance. In doing so, she revealed a hidden pattern that lurks in the skin of all birds.
The pattern of feathers on a bird’s body is set early on in its life, when it’s still inside the egg. When bird embryos are seven days old, they develop stripes of cells down their body where feathers will eventually grow. Over the next week, the stripes broaden out. As they expand, they lay down rows of cells called placodes, which will eventually produce feathers.
Two sets of chemicals – activators and inhibitors – set the pattern of the placodes. The activators promote the growth of feathers (as well as patterns in other animals), while the inhibitors are feather-blockers. These opposing chemicals can produce many different patterns depending on how they react with one another, the balance between the two, and the speed with which they spread through the skin (see footnote). By tweaking these variables, birds can evolve countless different patterns of feathers. The naked neck chicken provides a great example of how this works.