Duck School · Hatching
4 min guide
How to Candle Duck Eggs for Fertility
What candling can tell you, when to do it and why a gentle routine matters.
Candling means shining a light through an egg in a darkened room to look for signs of development. It can help you track a hatch, but it should be brief, gentle and purposeful rather than a daily curiosity check.
Use a clean, bright light in a dark room
Handle each egg carefully, hold it for the shortest practical time and keep the incubator closed as much as possible. A purpose-made candler can make the job simpler.
Make the first check around day 7
At about seven days, a developing egg may show a darker area with visible veins. A clear egg may be infertile, but shell colour and light quality can make it harder to see, so do not rush to a conclusion.
Keep a simple hatch record
Note the date set, each candling date and what you see. A brief record is more useful than opening the incubator again and again when you are unsure.
Quick answers
The questions people ask most.
How can I tell if a duck egg is fertile?
After incubation has begun, candling can show signs of development such as veins and a darker embryo area. Before incubation, you cannot reliably tell fertility from the outside of the shell.
What does a clear duck egg mean when candled?
It can mean the egg is infertile or development stopped very early. Shell colour and the brightness of your candler can affect what you see, so follow a careful candling schedule and avoid guessing too early.
How often should I candle duck eggs?
Keep it purposeful rather than frequent. A check around day 7 and another later check if needed is usually more useful than handling eggs every day.