The Truth About Chicken Sex Determination

At Uneek Poultry, we get asked this a lot: “If I adjust the temperature during incubation, can I hatch more hens?”

It’s a persistent myth—but it’s not true. In this article, we’ll explore the facts behind this popular belief, and why science says it simply doesn’t work for chickens.

The Origin of the Myth

Some reptiles—like turtles and crocodiles—can have their sex influenced by egg temperature. This process is called temperature-dependent sex determination (TSD). Naturally, chicken keepers started wondering: could this apply to poultry?

Here’s the Truth

Chickens don’t work like reptiles. In birds, the sex of the chick is determined at the moment of fertilization by the chromosomes in the egg. In chickens:

• Hens carry ZW chromosomes (they determine the sex)
• Roosters carry ZZ chromosomes

Once the egg is fertilized, the sex is locked in—temperature won’t change it.

No Scientific Evidence

Despite what some online posts claim, no valid studies have shown that incubation temperature changes the sex of a chicken embryo. A 2022 review in Avian Biology Research confirmed this across multiple bird species.

Why Does This Myth Keep Spreading?

• People prefer hatching more hens for eggs
• Coincidence is often mistaken for cause
• Online misinformation is easy to find

If temperature really worked, hatcheries would be using it globally. They’re not.

What You Can Control

• Accurate and stable incubation temperature
• Humidity levels
• Egg turning and hygiene

Focus on getting healthy chicks with a great incubator and good incubation practices.

The Bottom Line

Chick sex is genetically determined by the hen and cannot be changed by altering temperature. At Uneek Poultry, we help you focus on what really matters: healthy, strong hatches and informed poultry care.

FAQs

Q: Can temperature affect hatch success?
A: Yes—extremes or fluctuations can cause deformities or failed hatches, but they don’t affect gender.

Q: Is there any proven way to get more hens?
A: No reliable method exists. Sex is set by the hen’s chromosomes at fertilization.

Q: Can I buy only female chicks?
A: Yes—many hatcheries offer pre-sexed chicks, or you can choose auto-sexing breeds.

Need help with your incubator setup or choosing the right model? Contact Uneek Poultry – your local poultry experts.