We're just five days away from hatching now, and our chick is growing fast. There's very little room in the egg and what there is, is taken up almost completely by the chick and its yolk.
If we opened the egg at this point in incubation we'd see the chick now covered in down - although not the fluff we see in pictures : it won't look like that until several hours after hatching.
Carrying on from yesterday the chick's intestines continue to be drawn into its body and the yolk is now becoming more important in terms of providing nutrients throughout the rest of incubation, as the albumen (the white) of the egg is almost gone.
The incubated egg at day 16.
The bony structures continue to harden as the chorioallantoic membrane carries calcium from the shell to the chick, and as the chick loses moisture through the shell it's replaced by air so that the air cell, at the blunt end of the egg, is now growing quite large.
And finally today, some chicks (but by no means all) begin slowly to turn their position in the egg so that they move towards the best place for hatching, which is the head towards the blunt end. It's here the beak will 'pip' through into the membrane and then through the shell.
The chick is now filling so much of the egg that it's almost as easy to see inside by candling in a room with a light on, which is how the picture below was taken.
The embryo is the dark area covering progressively more area; the blood vessels are clearly visible underneath and the air cell is much bigger than it has been previously.
Below is a photograph in a darkened room; it's possible to see more or less exactly the same features here.
If candling today, you may be able to see movement in the lower area as the chick begins to prepare its position for hatch - but don't worry if you candle now and can't see it.
From now on, the growth of the darkened area and of the air cell is the best indicator that the chick is still growing.
We will be candling the eggs again immediately before 'lockdown' at Day 18. There's no point disturbing them before that.
Make sure your ventilation in the incubator is good to prevent the humidity levels rising too soon. If you're incubating in the Brinsea Mini Advance (or any other of Brinsea's small incubators) it's taken care of for you. In the larger Octagon 20 you need to make sure that the slider on the front of the incubator is at the midway point.
The only other issues for today are the usual temperature, humidity and turning reminders.
The humidity in my Brinsea Octagon 20 is too high - how can I reduce it?
On the front of this incubator is a slider which will open the vent, allowing more air into the incubator. This also reduces humidity at the same time.
I've found I need to experiment with this in different hatches. Begin by opening it and watching the digital readout on the lid. If it falls too low, close the vent a little and wait for it to stabilise before altering it again, if necessary.
My Brinsea Octagon 20 with vent and slider indicated.
Here's one of my lovely Light Sussex chicks, just three days after incubation ended.
This is what it's all about - hatching lovely, healthy, happy chickens!
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'The Incubated Egg' image is a commissioned artist's impression and, like all images on this site, is subject to copyright under the Copyright Law of the United States of America 1976.
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