Last year I had a few hatch that were really weird. The feathers were not embedded into the skin. I could clearly see the root of the feather sitting on the skin- it really looked bizarre. I had never seen anything like it before and never found out what can cause that to happen. In my hatch last weekend- I had another similar. The aircell on the egg was a really good size- but there was too much fluid in the egg- and the duckling was tiny. It was unzipping and I could see it very wet beak and the fluid starting to ooze from the egg. I had to remove a little shell and drain out some of the fluid to stop the duckling getting glued into place. When it was out of the egg- I saw that it too had the issues with its down. As it dried up the feathers fell off - now it has some bald stripes down its back. This has only happened when there is too much white left in the egg at hatching time- but I am wondering if maybe something similar has happened to your duckling. Poor ducky- I hope that as it grows it doesnt stay bald in on its head.
