Some definative points first.
1. The correct temperature for incubation is 37.7 degrees C and chickens
develop within a fairly narrow of tolerance to that temperature (more later)
2. They need humidity
3. There are a couple of different types of incubator - forced fan type or still air convestion types.
4. The eggs need to be turned to stop the embryos sticking.
5. The hen is moving the eggs constantly when she is brooding them.
1. Incubating eggs suffer much more from higher temperatures than they
do from lower temperature within a range of 1 degree C either side of
the 37.7. However 38.7 does more damage to the embryos than does
36.7. The lower temperature often means it simply takes a day longer for
them to hatch. A lower temperature than that and the embryos start to
Remember this is the core temperature of each and every egg. Hens get
up and leave eggs for varying periods of time to feed etc but the developing eggs (embryos) hold a temperature for quite some time but
they at 37.7 to begin with. All of them.
2. The humidity is needed to keep the membranes moist and allow the
chickens to move within the eggs whilst developing. There is also a relationship here to the turning of eggs to stop the embryo sticking to a particular side. Generally you find that the temperature begins to rise
quite dramatically if the moisture source dries out.
I have heard stories where early chickens embryos drown if the humidity is too high but IN MY EXPERIENCE I set eggs every friday and have the
same amount of water in the container all the time with no ill effects. Conversely, I have gone away for a weekend to come home and find that
the water has evaporated and I have a couple of chickens hatched and many more pipped but died in shell. Primarily becaue they couldn't rotate in the shell as the membranes dried and they adhered to one spot. They
quickly stress or run out of energy.
Provided the temperatures have not risen too much with the lack of
moisture (or for too long) the following week's hatches seem fine.
3. Types of Incubator. Most beginners incubators are of the convection
heat type. That is a heat source (each lights or a resistance element or similar) and it requires radiation (as well as some small convection currents of air) to warm the eggs. These are the most problematic types
of incubators as an egg to be too hot in one spot and too cold in another. These incubators are also effected by changes in ambient temperatures.
I use a remote temperature sensor placed amonst the eggs to give a constant indication of the average temperature within the incubator. For interest I bought this as a weather station off ebay out of china for less than $20 landed and its very accurate. Its a LCD thingo that sits on my desk and the sensor is in with the eggs in the incubator. I could have just
as easily use it with the sensor outside as a weather station and its good for about 20 metres transmission of information.
Regardless, the still air type of incubator is flakey although ultimately most people get them to work with a satisfactory result. They do need
quite a few batches of eggs to work through what is basically the idiosynchosies of an individual incubator. They work best with a full incubator than with just a few eggs. Fill it with supermarket eggs that wont
hatch if you need to make up the numbers. Throw them away after 21 days though as they will go off and explode.
The second type is the fan forced air type. The heat source is generally the same as the above type but it has a fan to blow the hot air around the
incubator and mostly it warms all the eggs to the same temperature. Because, all incubators need to be ventilated it draws in unwarmed air fresh air somewhere and blows out heated air somewhere else. Therefore
the temperature adjustment needs to be higher to maintain an even temperature. However they generally remain more constant once the adjustments are finally set up. BUT because of the movement of air big
changes of ambient temperature does affect them. You cant have a room
go from 22 degrees C to 2 degrees C overnight without affecting the incubator temperature. My current incubator is a foam Hovabator type to
which I fitted an old 80 mm computer fan to it. It works fine but topping up the water is constant chore as the fan encourages evaporation.
You set and stabilise the temperature with eggs in the incubator even if they are dummy (but real eggs) and over a few days then you add the eggs to be incubated. As the embryos develop they will develop (or better
store) heat and the incubator temperature can rise. I find that by incubating constantly in weekly batches, that the new eggs placed in the incubator counter balances the older egg's rising temperature. Thats just
my experience though.
4. Without doubt, the eggs need to be turned until the last few days before hatching. I separate the weekly batches with strips of cardboard to
act as partions but incubate standard and bantam eggs side by side. Bantams do hatch earlier but its only half a day or so. I turn the eggs in the morning and then again in the evening and thats it. We often have to
whizz down to Sydney for a variety of reasons and I am too old now (I feel that way anyway) to do a return trip in a single day. Its a four hour trip each way. So we stay the night in Sydney. The eggs dont get turned for anything up to 36 hours and we seem to get away with it.
As I said above, I have lost hatching chickens because of the lack of humidity causing water that has dried out while we were away.
Anyone on here will tell you (some have already) that it takes a number of batches and failures to get the balances right on your particular incubator. You will get it right and I just hope that some of my comments and experiences will help you. Keep at it, once you master it the joys are immense. Whew - hope I havn't bored everyone and please add corrections or comments. Some comments added by byp members
However I'm confused about temperature. Strangely, my incubator manual says it needs to be set at 38.5 for chicken eggs.
No - the manufacturer probably has the right temperature
recommendation for the temperature setting at the point where the thermometer hovers above the eggs. The eggs are below that and the
ideal core temperature of a developing egg is still the 37.7 degree C. If the heating element was closer to the eggs you may have found the temperature was too hot closer to the shell etc. I think you will also find
that this recommendation is at a constant 23 degree C. My incubator is in
the lounge with a slow combustustion fire in the same room. My cheapie temperature sensor, weather station lies amongst the eggs.
We are in the tablelands and at 700 metres above sea level and our current outside temp fluctuates between -6 and +20 C on a daily basis
although with the recent rains its been more like +2 to +12 C. We are also cold softies so we light the fire in march and it burns till september.
Don't forget that there are many variables that affect hatching vigor, some quite beyond your control. The main thing is to analyse what your
doing and keep at it - you will get it right.
This is my setup in the half re-painted lounge room. The incubator sits btween my egg candler and my spindly bonsai ficus which are having a
The incubator on the coffee table. Note my high tech candler on the left.
The inards. Yes I know it currently needs a clean. Note the temperature
sensor lying amongst the eggs. I dont even bother about the thermometer these days, just use the sensor. The strips of carbboard are
to separate the chronological batches of eggs.
This incubator may seem a bit grubby but it has now hatched about 300-
400 chickens with about 85% hatch rate after a few batch problems in the
beginning. I shut it down over the real hot summer period because its just
In answer to Dennis's question about the temperature rise when the humidity drops - I don't know - I guess dry air transfers heat better than
moist air ??? Denis wrote
Somewhere amongst your previous posts I did look up the instructions for
your incubator. It is exactly as Mike described. The temperature should read 38.5 degs at the top of the eggs, the instructions do explain that the
temperature of the eggs will be about 1 deg below this.
I wouldn't go messing around with humidity just stay with the manufacturers method for now. For your next batch you can weigh the
eggs, that is the best way to determine the rate of moisture loss from the
For all Mike's experience and success it should be noted he doesn't do much that is different from the manufacturers instructions. The observation that the incubator works best when it is FULL of eggs can be
found in instructions for a lot of incubators. Mike buys supermarket eggs
to keep his incubator full.
Ventilation is important too. I think a lot of people tend to close up their
vents in order to control temperature and humidity. Towards the end of
the hatch they need MORE oxygen and the vents should be fully open not
closed up in an attempt to increase humidity. Chookyinoz replied
And you are right, I am not an innovatist and incubation methods of chicken eggs has followed a pretty straight path for centuries. I do stick to
a known path.
The only real recorded deviation was when Cleopatra of the Nile hatched
a chicken from an egg incubated in her cleavage. Apparently thats true.
An old timer told me that if you put an incubated egg up against your eye
socket and it feels cooler than your eye socket then the temperature is too low and if feels warmer than your eye socket then it is too hot. I have
have done that in the past to measure differences in a still air incubator and you can notice the difference.
Despite very cold weather and big swings in ambient temperature I have
had another successful hatch yesterday and overnight in my hovabator.
Its fan forced and i have used a reading lamp over the intake air holes at
night to help stabiles the temperature. I had alrady removed five live chickens before this shot was taken this morning.
*image missing*Anybody - please feel free to contribute
Hatching & Brooding Chicks link:link