To determine if a chick has died inside its egg, the most reliable method is candling, a process of shining a light through the egg to observe its internal contents.
Candling for Viability
Candling allows you to monitor the embryo's development and identify non-viable eggs. This technique is typically performed in a darkened room using a strong, focused light source (like a candler or a bright LED flashlight) held against the large end of the egg.
Key Indicators During Candling
- Sign of Death: The Red Ring. A definitive sign that an embryo has died is the presence of a distinct ring of red visible within the egg. This "blood ring" indicates that while an embryo did begin to develop, its circulatory system has ceased functioning, and it has perished. Eggs displaying this sign should be promptly removed from the incubator to prevent potential contamination of other viable eggs.
- Sign of Life: Visible Blood Vessels. Conversely, if you observe intricate, branching blood vessels inside the egg, it signifies a live and thriving embryo. For chicken eggs, these blood vessels are normally observable within 7 to 10 days of an egg's incubation. As the embryo continues to grow, it will progressively fill more of the egg, and you might even detect subtle movements.
- Absence of Development. If, after several days of incubation (especially beyond day 7-10), you candle an egg and see only a clear egg with a yolk shadow, or a cloudy appearance without any defined structures or blood vessels, it indicates either an infertile egg or a very early dead embryo that has been reabsorbed.
Candling Timeline and Observations
Understanding what to look for at different stages of incubation can help you assess the viability of your eggs:
| Incubation Day | What to Look For (Live Embryo) | What to Look For (Dead Embryo/Infertile) |
|---|---|---|
| Day 3-5 | Small, dark spot (embryo), faint, delicate blood vessels. | Clear egg with no signs of development, or a "spider web" blood spot. |
| Day 7-10 | Visible embryo, expanding network of blood vessels, air sac clearly defined. Movement may be visible. | A distinct ring of red (blood ring), dark mass without defined vessels, cloudy contents. |
| Day 14-18 | Large, dark embryo filling most of the egg, significant movement. | No growth, contents appear cloudy or dark without clear structure, or a foul odor may be present. |
| Day 19-21 | Embryo filling the egg completely, air cell enlarged, movement, possibly chirping. | No signs of movement, no pipping, foul smell. |
Other Indicators of a Non-Viable Egg
Beyond candling, several other signs can suggest that a chick has died inside the egg:
- Foul Odor: A strong, putrid smell emanating from an egg is a clear indication that a chick has died and the contents are decomposing. This is often referred to as a "rotten egg" and can be quite unmistakable.
- External Appearance Changes: While less common, a dead egg might develop a crack or leak due to internal pressure from decomposition, or it may feel unusually cold compared to surrounding viable eggs.
- Lack of Movement or Sound: As the incubation progresses toward hatching (especially after day 18), a live chick becomes very active, and you might hear faint chirping or peeping sounds. A complete absence of any internal movement or sound, coupled with no pipping by the expected hatch day, strongly suggests the chick has not survived.
- No Pipping by Hatch Day: For chicken eggs, if the 21st day of incubation arrives and there is no sign of pipping (the chick breaking through the shell), it's a significant indicator that the chick is not alive or has failed to thrive.
Importance of Removal
Promptly removing dead eggs from the incubator is crucial. A decaying embryo can generate harmful bacteria and gases that can contaminate other viable eggs, potentially jeopardizing the health and success of your entire hatch. For more detailed insights into the incubation process, consider consulting a comprehensive 21-Day Guide to Hatching Eggs.
