Day 17 is probably the day where least of all can be seen, and there is less to do than at any almost other day during the incubation process.
There is still advancement within the egg, but the chicken egg development stages are almost complete.
This is not a good day to candle the eggs. We will candle every one tomorrow (day 18) as we lock the incubator down for hatch.
At this point it's crucial that the chick is moved a little as possible, to enable it to turn into the right position.
In any event, there's very little to see. The chick fills almost the whole egg now, all we can see is a dark area – this is the chick's body.
The slightly lighter area underneath the dark in the photograph below is the yolk. The very light area at the bottom is the growing air cell.
You may be able to see very light-coloured markings on the air cell. This is where I've candled at Days 7, 12 and now 17 and marked the air cell each time.
You can see from the arrows how much it's grown in those ten days.
These markings have two purposes. They tell me the chick is still growing, and they tell me more or less where the chick should begin to break through the shell in just a few days' time.
Today, we should make sure temperature, humidity and turning the eggs are consistent, as they have been for every day of incubation so far.
Tomorrow, we will be preparing the incubator for hatching, candling for the final time and adjusting humidity and ventilation levels.
Bantams often hatch earlier than large breeds, at around day 19 or 20. If you have bantams in your incubated eggs you can stop turning them today.
If your clutch of eggs is mixed bantams and large breeds, you can choose to lock them all down today.
Should you decide to take action today, here are details of how to lock down your incubator.
Lockdown is simply the last three days before hatching. It involves...
And here's what we're aiming to produce over the next few days: a healthy, happy little chick from each incubated egg!
This is one of my Wyandotte chicks at 5 days old. Notice her wings are already starting to grow. She was trying to use them to fly out of the brooder by the end of week 1!
To return to the overview of this 21-day hatching process, use the first button link below. To return to day 16 and refresh your memory if necessary, use the second link. To move on to the next stage, use the day 18 link.
A lot of "facts" you'll find on the internet are often people's individual views, based on inaccurate information repeated from poor quality sources.
The information I provide in this article and others is based on both my own experience of incubating and hatching chicken eggs every year for over 13 years, but on evidenced facts from scientific, peer-reviewed research and books from highly respected and experienced poultry keepers such as Gail Damerow.
Some of the trusted sources I have used in this article are these.
Avitronics: Heart Rates. Pub. Avian ID, 2020.
Damerow, Gail: Hatching and Brooding Your Own Chicks. Pub. Storey, 2013. See my review, here.
Hall, C., et al: A new candling procedure for thick and opaque eggs and its application to avian conservation management. Pub. Journal of Zoobiology, 2022.
Hamburger, V and Hamilton, H L: A series of normal stages in the development of the chick embryo. Pub. Journal of Morphology, 1951.
Leonor, H., and Chaveiro, S: The Effect of Candling on the Hatchability of Eggs from Broiler Breeder Hens. Pub. Journal of Applied Poultry Research, 1993.
Phuphanin, A., et al: Smartphone-Based Device for Non-Invasive Heart-Rate Measurement of Chicken Embryos. Pub. National Center for Biotechnology Information, 2019.
Vargas, R., et al: Egg Candling Analysis Equipment Design: A Safety Solution. Pub. Journal of Social and Behavioural Sciences, 2018.
Wu et al: Egg fertility and reduced egg fertility, hatching success, and larval survival. Pub. Science Direct, 2003.