As the eaglets start to sprout feather cloaks, we’re getting questions about natal down, thermal down, and juvenile feathers. Unless otherwise stated, the information in this blog applies to altricial birds, although most research in this area has been done on precocial and semi-precocial birds like ducks, geese, and cranes. Altricial and precocial birds have some marked differences in pre-hatch follicular development and post-hatch molts. Does thermal down sprout from natal down pores? Do flight feathers emerge from thermal down