Sexing Chicks: Myths and Realities

While some methods of sexing chicks are scientific (like DNA testing or vent sexing), the world of backyard poultry is full of "folk wisdom." Most of these are about as accurate as a coin toss, though a few have a tiny grain of truth buried in them.

Here is a breakdown of the most common myths and wives' tales for sexing chicks.

Pre-Hatch Myths (The Egg)

These methods claim you can tell a chick's sex before it even leaves the shell.

The Egg Shape: This is the most famous myth. The legend says that pointy or narrow eggs are roosters, and round or blunt eggs are hens.

• The Reality: Egg shape is determined by the hen’s oviduct, not the chick's DNA. However, modern research (as of 2025–2026) using machine learning has actually found a roughly 80% correlation between "shape index" and sex, but it requires precise mathematical measurements, not just a quick glance.

The Pendulum (Ring on a String): Similar to predicting a human baby's sex, some people hold a wedding ring or a needle on a string over the egg. If it swings in a circle, it’s a hen; if it swings back and forth, it’s a rooster.

• The Reality: This is purely a form of "divination" and has 0% scientific basis.

Candling for Sex: Some believe that by looking at the air sac or the "shadow" of the embryo during candling, you can spot a rooster.

• The Reality: You can see if an egg is fertile or alive, but there are no visible differences between male and female embryos to the human eye.

The Air Sac Position Test:

• The Myth: If you "candle" the egg (shine a light through it) and the air cell is perfectly centered at the large end, it’s a male. If the air cell is off to the side, it’s a female.

  
  

• The Reality: The air cell moves and grows as the egg loses moisture during incubation. Its position is determined by the mechanics of the membrane separating, not by the gender of the chick.

The Hatch Order Myth:

• The Myth: The first chicks to hatch are always the roosters because they are stronger; the stragglers are the hens. (Or sometimes the reverse is claimed).

  
  

• The Reality: Hatch time is determined by the age of the egg before incubation, the temperature of that specific spot in the incubator, and the vigor of the individual chick. Gender is not a factor in hatch speed.

The Moon Phase Myth:

• The Myth: If you set eggs to incubate during a specific phase of the moon (usually a waxing moon), you will get more hens.

  
  

• The Reality: This is agricultural folklore. Since sex is determined at the moment of fertilization (before the egg is even laid), the moon phase during incubation cannot retroactively change the chromosomes.

Placing Eggs in Refrigerator Prior to Incubation "Preferential Mortality"

Unlike the other myths (which claim to change the sex), this myth claims to filter the sex. While there is a "scientific" origin story to this idea, it is widely considered debunked and dangerous practice for anyone wanting a high hatch rate.

The Idea: The theory suggests that male embryos are weaker and less resistant to cold stress than female embryos. Therefore, if you refrigerate the eggs for a few days before incubating, the male embryos will die off, and only the "tougher" female embryos will survive to hatch.

• The Origin: This belief stems largely from a single Australian study published in 1960. The researchers claimed that storing eggs at 40°F (4°C) for several days resulted in a hatch of roughly 55% females because more males died in the shell.

  
  

The Reality: Why it Fails

Since that 1960 study, poultry scientists have tried to replicate those results and failed. Here is the modern consensus:

• Equal Mortality: Modern research indicates that while cold stress does kill embryos, it kills them indiscriminately. You are just as likely to kill a female embryo as a male one.

  
  

• Drastically Reduced Hatch Rates: A standard home refrigerator (approx. 35–40°F / 1.6–4°C) is too cold for hatching eggs. The ideal storage temperature for hatching eggs is 55–60°F (13–15°C)—think "wine cellar," not "fridge."

  
  

• Dehydration: Refrigerators are dehumidifiers. Placing porous eggs in a fridge sucks the moisture out of them rapidly, damaging the air cell and often killing the embryo regardless of sex.

The Incubation Temperature Myth:

• The Myth: Incubating eggs at higher or lower temperatures will influence the gender of the chicks (similar to how temperature determines sex in reptiles like crocodiles or turtles).

  
  

• The Reality: Birds are not reptiles. As mentioned above, a chicken's sex is genetic and determined the instant the sperm meets the egg. Temperature fluctuations may affect hatch rates or health, but they cannot change a female embryo into a male one.

  
  

The "Handling" Myths

These methods involve picking up the chick to see how it reacts. Caution: Some of these can be stressful or harmful to the bird.

The Scruff Test: If you pick a chick up by the scruff of its neck and it lifts its legs, it’s a hen. If its legs hang limp, it’s a rooster. (Sometimes the rule is reversed depending on who you ask).

• The Reality: This is highly unreliable and essentially tests the chick's "freeze" response to a perceived predator.

The "Flip" Test: Laying a chick on its back in your palm. If it kicks and fights, it’s a rooster; if it stays calm, it’s a hen.

• The Reality: This is actually dangerous. Flipping a chick on its back can trigger "tonic immobility" (a fear-based paralysis) or even restrict their breathing. It tell

  s you more about the chick's individual personality or stress level than its sex.

  
  

Visually Sexing a Chick

Only works on specific types of breeds and is not a universal trait amongst all chicks.

• Wing Feather Sexing: This only works on specific breeds where the hen is a "fast-feathering" variety and the rooster is "slow-feathering." In these chicks, the female’s wing feathers will show two distinct rows of different lengths, while the male’s feathers will be the same length. To "wing feather sex" a chick, you are looking at the length of the primary wing feathers compared to the covert feathers.

  
  

It is important to know that you cannot feather sex just any random chick. It only works if the chick inherits a specific sex-linked gene for feather growth speed. ​You can wing feather sex chicks in three specific categories in Commercial Hybrids:​

• White Hybrids: ISA White, Dekalb White, Bovans White, and Hisex White. ​

• Brown Hybrids: Many strains of ISA Brown/Production Red, Lohmann Brown, and Hy-Line Brown (though some of these are also color-sexed).

• Broilers: Almost all commercial meat birds, such as Cornish Cross, can be wing feather sexed at the hatchery.