| Each feather looks like a miniature straw at first. Then, that smooth outer case—called the sheath—crumbles and allows the developing feather to open. Image:
L. Birbaum
|
| Each feather looks like a miniature straw at first. Then, that smooth outer case—called the sheath—crumbles and allows the developing feather to open. Image:
L. Birbaum
|