Why do we need to keep humidity at a certain level?

[ohnoicantfly]

Use a calibrated hygrometer/thermometer in the incubator never trust the incubator gauges. inside that incubator is gonna be a different environment because it’s closed off and hotter in there.

I have a hygrometer that has a built-in a thermometer It reads 15% in the bator without any added water, and 30-35% in my house.

 

[cmobley]

I have a hygrometer that has a built-in a thermometer It reads 15% in the bator without any added water, and 30-35% in my house.

But have you calibrated it to see if it’s reading right.

 

[nuthatched]

Hello all! I've been genuinely curious about this for a long time. How come we have to monitor humidity in an incubator, when a broody hen hatches her clutch without even having an idea of what humidity is? Does she somehow regulate humidity for the eggs? Really just curious here!

Humidity is too make sure the egg doesn't loose too much moisture, the under side of a hen 'sweats' a bit to maintain Humidity. Incubators mimic that process

 

[Ridgerunner]

Does she somehow regulate humidity for the eggs?

Several years ago there was a thread on here where a few people put hygrometers under a broody hen to answer this question. This was not a strictly scientific experiment where everyone used the same equipment and parameters but some people said the hen could apparently regulate the humidity.

But the main reason for the whole humidity thing is a egg is supposed to lose so much liquid in so many days so the chick can pip and have a big enough air cell to breathe while it’s trying to break the shell. Also lubes the membrane so the chick can turn and unzip. If it loses to much liquid to fast it’s called shrink wrap and when the chick pips the shell open the membrane dries on the chick like glue the chick can’t move and breathe and dies.

The good thing about this is that nature gave us a fairly wide window of moisture loss for this to work instead of a specific number. You don't have to be that precise. But it is a window that you need to hit. If the moisture loss is too high or too low it causes problems.

If humidity in my house is about 30-35%, why does it read 15% in the incubator

Dew Point is a measure of how much moisture is in the air. At what temperature does the humidity hit 100%. That is not what you are measuring. Humidity is a measurement of what percentage of moisture is in the air compared to what it could hold at that temperature. Hopefully your house is not the same temperature as the temperature inside the incubator so their capacity to hold moisture is different.

There is no perfect humidity for all of us. Each incubator is different, each egg is different. The temperature and humidity where we have our incubators is different. Even you height above sea level can influence how much moisture the eggs will lose. Eggs lose moisture as they are being stored, waiting for incubation to start. As someone mentioned, even a storm front moving through can change the humidity inside the incubator. What we are after is not a specific humidity all the time. What counts is the average humidity over the entire incubation.

Commercial hatcheries that may have 60,000 eggs in one incubator really fine tune humidity. If they move an incubator to a different part of the incubating room they may have to adjust the humidity. To them even a tiny difference in hatch rate can be noticeable where with us it is not noticeable until it gets larger. We don't have to be that precise.

What I usually suggest is to try a certain humidity. Be as consistent as you can and evaluate your hatch. Open the unhatched eggs to determine what affect humidity may have had on your hatch. That's not easy as many things can affect the hatch. After trial and error I determined that an average humidity of around 40% was my sweet spot. Other people find that their sweet spot may be quite a bit lower or higher.