I checked the East nest this morning while the duck was out and all of the eggs on the top layer were pipped. Thus I expect hatching will occur starting tonight or early tomorrow and that would make their jump day Saturday.
Also a surprise: there are now 3 eggs in the West nest. There were none just two days ago after two weeks of brief visits, so that led me to predict in the previous post that there would not be a round two for the West nest box. I should know better. Whenever I predict something (for a good example, see the paragraph just above and the headline of this posting) the ducks like to fool me. I should just stop doing that and instead always write “we’ll see” instead.
The last stages of hatching occur when the duckling uses its “egg tooth” to break through the egg membrane into an air pocket that forms in the egg between the membrane and the shell. At this time the egg white has been fully absorbed and the yolk is becoming internalized in the duckling, so there’s no free moisture inside. The duckling breathes in this air pocket and there is some air exchange through the shell, which is porous.
A while later the duckling adds to the air exchange by pecking at the egg shell in one spot (wherever its little beak is), which is called pipping the egg shell. That lets in more air.
Since the duckling is breathing it can make sound and I’ve heard faint peeping when holding a pipped egg. I think this stimulates the hen to be even more active than usual in turning the eggs. Hours later, about a day or so after pipping, the duckling has developed enough to use its legs to push and to very slowly rotate inside the egg as it pecks with its egg tooth. It takes many hours to break the egg all the way around and to finally emerge. The egg tooth is a sharp spur at the end of the ducklings bill. You can see it as a white spot after they hatch: