How do hens control humidity in natural incubation?

In all the instructions about how to hatch eggs in an incubator it is said to run a certain temp for the duration of incubation but to raise the humidity a significant amount during the last three days of incubation.

It makes me wonder how the hen raises the humidity during the last three days of natural incubation?

Can’t seem to find an answer on the web, only more charts of recommended days, temps and humidity levels.

Hope to hear from someone very soon, it is a question that’s been buggin me for quite a while.

Thanks.

joker468 said:

In all the instructions about how to hatch eggs in an incubator it is said to run a certain temp for the duration of incubation but to raise the humidity a significant amount during the last three days of incubation.  

It makes me wonder how the hen raises the humidity during the last three days of natural incubation?

Can’t seem to find an answer on the web, only more charts of recommended days, temps and humidity levels.  

Hope to hear from someone very soon, it is a question that’s been buggin me for quite a while.

Thanks.

Click to expand...

Good question! Once a broody hears the chick peeping from its internal pip, the do not get off the nest until they decide all the chicks have hatched. The eggs get their moisture from direct skin contact under the broody, part of the reason they pluck out their breast feathers, too.

my hens get off the nest once everyday up to and including the last three days

It's one of those mysteries of life. God made chickens to do what they do best. My chickens also stay on the nest once the chicks start hatching. I figured that's how the humidity was taken care of. The heat and natural moisture from their body keeping the eggs in exactly the right conditions. I don't know where the "rules" of humidity in artificial incubation came from. Did someone stick a hygrometer under a hen? Was it learned through trial and error? All I know is, my broodies have a much better hatch rate than I do. (But I can hatch more at a time ) I've never thought to wonder how the hen's humidity is controlled. Just that it is.

I had a broody hatch eggs for me and two died after they pipped. They both looked like they had the "shrink wrapped" issue. Three others did not pip at all. Four hatched healthy on day 21. If my hen came off of the nest/eggs to eat/drink/etc. for a few minutes, would that have been enough to cause this to happen to the chicks? She has now started (day 23) to get off the nest with the live chicks. I haven't tossed the three unhatched eggs, but they are probably lost at this point (I have not heard any noise/seen any movement from them).

When the eggs are near their due date the hens stop turning and they sit tight on their eggs so that is why we have a lock down during hatching. I am sure the humidity levels do not get as high under the hen as many people use for hatching but I am guessing the humidity levels under the hen increase a bit during hatching to keep the chicks lubricated in the shell, possibly as a result of the hen's reduced movement and the wet mess of the eggs hatching under her feathers. I also wonder if using higher humidity levels are primarily a means of compensating for a lack of natural oil coating on the eggs in the incubator that may hold in more moisture versus the eggs under a hen and also for fans that circulate warm air in the incubator and dry out the eggs.

The higher humidity level during hatching is a means of preventing chicks from getting shrink wrapped during hatching but the inside of the egg is so moist that it should be adequate for hatching as long as a fan does not dry the eggs out too much. Perhaps hens do more assisting their chicks than we realize too while we sit back and hope the chicks will hatch entirely on their own if the settings are just right. I personally find that once hatching begins my humidity level increases in the hatching incubator so I try not to start out too humid for fear of the chicks drowning in the shell.

I occasionally have chicks hatch early in my incubation incubators where I use dry hatching (it is pretty humid here) so I think that humidity does not need to be as high as people recommend. I have hatched many chicks in dry high altitude regions and all I did was put water in the reservoir of the hatching incubator so I am sure my humidity was below what is recommended. People often ask me how I hatch with success and I have to say it is by doing what works rather than going by what I have read.

I always had good hatches with little effort in my Little Giant styrofoam incubators, which I have used successfully for many years. As soon as I started monitoring temp and humidity more closely to follow recommendations, my hatch rates suffered (presumably from too much humidity).

I use forced air for chicks and still air for ducklings so the duck eggs are incubated at a higher humidity that way to. Adding water and/or misting the eggs to simulate a wet hen duck returning to her nest after a bath did not improve my hatches so I don't bother. They seem to incubate fine with the humidity of our climate so that makes hatching simple.

bobbi-j said:

It's one of those mysteries of life. God made chickens to do what they do best. My chickens also stay on the nest once the chicks start hatching. I figured that's how the humidity was taken care of. The heat and natural moisture from their body keeping the eggs in exactly the right conditions. I don't know where the "rules" of humidity in artificial incubation came from. Did someone stick a hygrometer under a hen? Was it learned through trial and error? All I know is, my broodies have a much better hatch rate than I do. (But I can hatch more at a time

) I've never thought to wonder how the hen's humidity is controlled. Just that it is.

Click to expand...

that made me laugh but i was looking up the same question.. it’s a valid question when it seems it’s so particular in an incubator