How long till hatching after internal pip on a wood duck?

[jsvand5]

My lone wood duck egg has finally internally pipped. I first noticed it saturday night. I can see the duckling moving around quite a bit in the air cell. So far there has not been any external pip, and I have not heard the duckling at all yet. Any ideas on a time frame until I should see some progress. I really want this thing to hatch since it is the only egg from the clutch. A bit of good news is that it looks like my pair is laying another clutch. Hoping she'll do better on this one but she only lays one egg every couple of days for some reason.

 

[Boggy Bottom Bantams]

I've seen them go from 1-3 days