Category: Incubation

Humidity is one of the most important factors determining your hatch rate, but, contrary to popular belief, high humidity is more troublesome than low humidity during most of the incubation period. 

During hatch, of course, you want high humidity in the range of 65% or more so that the chicks won’t get stuck in the shell, but the goal is 40 to 50% for the first 19 days.

In order to hatch correctly, a chicken egg should lose 13% of its weight during incubation, and that weight is lost in the form of water evaporating out of the egg.  Over time, the air pocket in the egg will get larger as water evaporates out, creating a safe spot for your chick to breath in between around day 19 and the time the chick hatches.  If the humidity in your incubator is too high, then your chick won’t have the appropriate air pocket and will die soon before pipping.

There are a few different ways to get the right humidity in your incubator.  The simplest is to follow the instructions and fill a certain number of wells with water, but this is a very hit or miss approach — humidity in your incubator is determined by the humidity outside the incubator as well as by the amount of water in the wells.  We live in a very damp climate, and I suspect that following the instructions last time around is part of what resulted in such a low hatch rate.

The second method is to pencil the size of the air pocket on the outside of each egg at intervals while candling.  A chart like the one shown here can be used to see if the egg’s air pocket is growing at the right speed.  However, this technique requires a lot of judgement calls, and would be time consuming if you’re hatching more than a few eggs.

Another easy method to get the proper level of humidity is to buy a fancy incubator with a humidity readout.  Our new Brinsea Octagon 20 incubator will definitely help us in that regard, but there’s a big difference between 40 and 50% humidity and I’d like to know whether my eggs are losing weight at the proper rate.

Which brings us to the final method of determining egg weight loss — weighing your eggs.  This is the method I’ve chosen, so I’ll go over the specifics of the calculations in a later post.

No matter which method you choose, you should be aware that it’s the average humidity over time that’s important to your eggs, not the humidity at any given moment.  So it’s okay to let the incubator wells completely dry out for a day if you need to in order to get the average humidity down lower.  In fact, some incubation experts practice dry incubation where they seldom or never fill the wells at the bottom of the incubator.  I plan to use a hybrid approach, adding water as needed to keep our
eggs’ weight loss on track.

After several rounds of trial and error, I figured out the best way to incubate chicks.  You can read the blow by blow experimentation here, or splurge 99 cents on my ebook for the more refined solutions.

Our first trial hatch in the Brinsea
Mini Advance incubator was better than I’d expected but worse than I’d hoped.  Four eggs  out of seven pipped, two chicks hatched, and one survived.  Although it was emotionally tough, I chose to autopsy all of the dead eggs in hopes of improving my hatch rate for next time.

• One chick was speared by
  another’s claw as it tried to hatch.  The dead chick was hatching about half an hour later than its sibling and had just reached the stage where it was beginning to push the mostly detached egg top aside when its precocious sibling clambered over top of it and stuck its foot inside the crack.  In a way, this is a crazy fluke, but the experience also makes me think that it might be smart to have somewhere else for newly hatched chicks to fluff out rather than on top of their
  hatching siblings.  Since I’ve read that it’s best not to move chicks to the brooder until they’re fully fluffed out, that means a spare incubator or other enclosed, warm space.
• Another chick started pipping, but only seemed able to push small chips out of its shell.  (I’ve enlarged the hole after death to see in.)  I don’t know whether
  the shell was abnormally hard or the chick was abnormally weak.  I’d read not to help chicks out of the shell, so I stood back, and the chick eventually perished (perhaps in part because an earlier hatched chick (not the same one as above) rolled the egg over so that the hole was face-down on the ground.)  Since the chick died anway, I wonder if
  I wouldn’t have been better off helping this obviously struggling chick?  On the other hand, it might have come out weak and had to be culled anyway.
• Three eggs had nearly full-formed chicks inside but they didn’t manage (or, apparently, even try) to pip.  Some sources suggest that late stage dead in shell chicks are signs of incorrect humidity, often too high.  I didn’t keep track of the size of the air pocket over time by candling, but I may try that next time around to help me keep the humidity in the right range.
• Finally, one chick hatched on day 22 but died less than a day later.  Chicks that hatch late and are “soft” are indications of the average incubation temperature being lower than optimal, and temperature was definitely the spot where I did the worst job during incubation.  Air temperature in the kitchen fluctuated between 45 degrees and 85 degrees and the incubator’s high and low temperature alarms went off several times.

The good news is that all of the eggs were viable and made it nearly to hatching time, which means our rooster and hens are all fertile.  And watching the first chick hatch was quite an experience — well worth the price of the incubator by itself!  Hopefully I can fix my mistakes and have more living chicks next time.

Since writing this post, I’ve experimented much more with incubation.  I developed a dichotomous key that makes it easy to figure out exactly what went wrong (and how to prevent the problem from reoccurring).  Learn more about troubleshooting the hatch in my ebook.

Permaculture Chicken: Incubation Handbook walks beginners through perfecting the incubating and hatching process so they can enjoy the exhilaration of the hatch without the angst of dead chicks. 92 full color photos bring incubation to life, while charts, diagrams, and tables provide the hard data you need to accomplish a hatch rate of 85% or more.