Hi, guys. I joined up yesterday to learn all I can - a crash course - about duck egg incubation. I've posted in the ducks section, but thought asking a question here would be a good idea, too. I have never taken care of an egg before and know virtually nothing. My daughter found a what we think is a mallard egg along the sidewalk outside her school (the whole story is in the new members thread and the ducks thread) and we're now on Day 19 of incubation. I'm using a hova-bator circulated air incubator with automatic rocking racks, borrowed from our 4H office. The egg is on its small end, at 99.5F. I've candled it a few times and the baby is alive and growing. It seems to be the appropriate size according to the number of days of incubation. Main concern at this point is the size of the air cell. It's about the same size as it was on Day 1 - roughly the diameter of a nickel. I tried removing all of the water cups to decrease the humidity (it was around 40 percent according to my very old and probably unreliable gauge), and now it reads around 35 percent. I plan to candle it this evening to see if the air cell size has increased, but want to be sure 35 percent humidity is acceptable. (After reading about dry incubation, it sounds like it's okay; though I don't know if the same rules apply to ducks.) Can anyone explain the growth of an air cell on a mallard egg? Can I use the air cell size alone as an indicator of proper humidity? I'm also cooling and misting the egg every evening. I use warm water, and let it evaporate before returning it to the incubator. It's out for around 5 to 8 minutes each time. Any advice and suggestions will be gratefully appreciated.