*This is by my experience alone and not from another source, it works for me and I've had very successful hatches with Call ducks. Disclaimer: this is not medical advice for your ducks please hatch at your own risk.
I wish you the best!
If your ducks are on a good calcium diet- the eggs will be strong. It's imperative the humidity levels never drop and are raised during lockdown to soften the shell.
100℉ *circulated air
Before Lockdown (62% ideal) 60-65% Humidity depending on duck species
Lockdown (75% ideal)
Inner Pip: When the beak breads through the inside sack and breathes for the first time.
Outer Pip: The pip you can see, a small hole to allow the chick to breathe and get ready for zipping.
Zipping: Final hatching stage. This process should take no longer than 2 hours. For call ducks it’s best to help if they cannot zip and finish after 1 hour.
Malpositioned Zipping: A secondary pip hole appears without a zip pattern- monitor heavily this may need assisting.
Assisting a hatch: The egg’s walls and the outside of the chick is covered in live blood vessels. They are still there during the outer pip phase, do not assist a chick at this time it is too early. The baby will start zipping once all blood vessels have been absorbed. You cannot assist a hatch until all blood vessels are absorbed.
Environment during an assisted hatch: Warm and humid. An option, the bathroom. Close all doors and windows then turn on the water to high heat for a few minutes.
If you spray with a mist water bottle it must be an even light coating of water. Do not form droplets on the egg, this will ruin the bacteria barrier and cause issues or fatality. If Humidity plummets, lightly spray once an hour for 3 hours. During this time correct the humidity levels by adding water below. Do not overcompensate with higher humidity levels. Water still needs to evaporate from the embryo sack or else the chick will drown.
YELLOW membrane (paper like layer under the hard shell) : IS BAD, this means it has dried up. Either the chick is dead or dangerously stuck. If the humidity is too low or you open the incubator and let out too much humidity (that’s why we lightly mist) it can immobilize the chick to hatch.
WHITE membrane: Healthy and the way you want it.