If you’re new to raising chickens, “candling” eggs might sound a bit odd. It’s actually a simple and safe way to check on developing eggs by shining a light through them to see what’s happening inside. Candling can tell you if an egg is fertile, if the chick is growing well, and help you catch any problems early. It’s also an exciting way to get a firsthand look at a chick’s growth, turning a small task into a rewarding part of your chicken-keeping journey. Let’s go over what candling is, why it’s helpful, when to do it, and how to tell if an egg is fertile and on track.
Why Candle Eggs?
Candling eggs during incubation gives you a peek at the progress inside each egg. Here are some of the main reasons why chicken keepers candle their eggs:
- To Check Fertility: Eggs don’t show any signs of fertility from the outside, so candling gives you a way to see if there’s life forming. This helps you separate the viable eggs from the non-viable ones, which is especially useful if you have several eggs in an incubator.
- To Track Development: Candling is a way to track the chick’s growth over time. By candling at different points during the incubation period, you can tell if the chick is developing on schedule. It’s amazing to see the little changes as the chick’s body takes shape.
- To Remove Non-Developing Eggs: If an egg isn’t developing, it could start to rot, which can spread harmful bacteria and affect other eggs. Candling helps you spot eggs that aren’t viable so you can remove them, keeping your incubator safe and clean for the healthy eggs.
When to Candle Eggs
You don’t need to candle your eggs daily, and it’s best to handle them as little as possible. Most chicken keepers candle their eggs three times during the incubation period:
- Day 7–10: After about a week, you should be able to see the chick beginning to develop. You’ll likely spot some blood vessels forming and a small dark spot, which is the embryo. You might even see a bit of movement if you’re lucky.
- Day 14–16: By two weeks, the chick should be larger and easier to see. You’ll notice more blood vessels, and the shape of the chick will start to take form. Its body may begin to fill more of the egg, and it’ll look darker overall.
- Day 18–21: In the final days before hatching, the chick will have taken up almost the entire egg, so the inside will look mostly dark. You should be able to spot an air cell near the large end of the egg, which is where the chick will take its first breath before hatching.
Candling on these days lowers handling while also giving you a good idea of the chick’s progress. Avoid candling too often to keep the eggs at a stable temperature and humidity, which is very important for their healthy development.
How to Candle Eggs
A regular flashlight works well, or you can use an egg candler, a small light designed just for this purpose. Here’s how to candle eggs safely:
- Set Up in a Dark Room: For the clearest view, candle in a dark space where the light can shine directly through the egg without interference.
- Hold the Egg Gently: Place the egg in your hand and hold it above the light source. Be careful not to shake or drop it. If you’re using an egg candler, it might have a soft ring to help hold the egg securely and prevent it from slipping.
- Shine the Light Through the Egg: Position the light against the broader end of the egg, where the air cell is located. Shine it through and observe what’s inside—look for blood vessels, the embryo, and eventually the chick’s shape. Slowly rotate the egg if needed, but try to handle it briefly.
- Observe Development: Look for signs that the chick is growing well. Note any changes from the last time you candled, and consider taking pictures to track progress if you’re candling multiple times.
- Return the Egg Quickly: Avoid leaving the egg out of the incubator for too long. The exposure to cooler air can disrupt development, so after you’ve checked each egg, place it back in the incubator as soon as possible.
How Can You Tell If an Egg is Fertile?
Candling can help you spot fertility early in the incubation period, usually by Day 7–10. Here’s what to look for in a fertile, developing egg:
- Early Signs (Day 7–10): A fertile egg should show signs of life within the first week. When candling, look for a small dark spot, which is the embryo, surrounded by branching blood vessels. This “spider” pattern is a good indication that the egg is fertile and developing.
- Clear or Opaque Eggs: An egg that looks clear with no visible blood vessels or embryo is probably not fertile or has stopped developing. If there’s no sign of growth by Day 10, it’s safe to assume it won’t develop further, and it can be removed from the incubator.
- Changes as the Chick Grows: As the chick develops, the dark area inside the egg will grow larger, and the shape of the chick becomes more visible. By Day 14, you might start to see the outline of the chick’s head and body.
- Movement: If the egg is fertile and the chick is growing well, you might spot some movement during candling. Even a small wiggle or shift in position is a reassuring sign.
Whether you’re just starting out or have been raising chickens for a while, candling is a hands-on way to ensure your eggs are progressing smoothly. By candling at the recommended times and handling your eggs carefully, you can increase your chances of a successful hatch and also be able to protect your eggs from rot.
Curious about candling your eggs and more? At Poultryperch, we’re here to guide you through each step of the poultry raising journey. Explore our helpful guide and learn everything you need to know about raising chickens!
