Determine Chick Gender: Myths & Tips and is it possible to create more hens

Can I influence the gender of my unincubated eggs?

The short and rather disappointing answer is no! Here’s what’s actually going on:

What determines chick sex?

In birds (including chickens and quail), sex is genetically fixed at the moment the egg is formed, not during incubation:

Hens have ZW chromosomes

Roosters have ZZ chromosomes

The hen’s egg decides the sex (unlike humans, where the sperm does)

So by the time the egg is laid, it’s already “set” to be male or female. Nothing you can do will change this but here are some common misconceptions that you will come across.

Does egg age affect gender?

There’s no scientific evidence that older eggs produce more females (or males). Egg age:

Does NOT influence sex

DOES affect hatch success (older eggs are less likely to hatch well)

What egg age does affect

If anything, older eggs can:

Have lower hatch rates

Produce weaker chicks

Be more prone to embryo death

But among the chicks that do hatch, the sex ratio stays roughly 50:50.

Why the idea exists

People sometimes notice patterns (e.g., “these older eggs gave me more hens”), but that’s usually due to:

Small sample sizes

Random variation

Incubation conditions affecting survival (not sex itself)

Bottom line

Egg age ≠ chick gender

Sex is determined before the egg is even laid

Older eggs just mean lower quality hatching, not different sexes

Does the shape of an egg indicate gender? No—the shape of an egg (rounded vs. pointed) has nothing to do with the sex of the chick inside.

Why this myth exists

There’s a long-standing folk belief:

Pointed eggs → males (cockerels)

Rounder eggs → females (pullets)

But this has been tested many times, and the results show no reliable correlation.

What actually determines sex

As mentioned earlier:

The chick’s sex is fixed genetically when the egg is formed

The hen contributes either a Z or W chromosome, which decides male or female

Egg shape forms later and is influenced by physical factors, not genetics of sex

What does affect egg shape

Egg shape can vary due to:

The hen’s breed

Age of the hen

Oviduct shape and muscle tone

Occasionally stress or minor shell formation quirks

None of these are linked to whether the chick is male or female.

Scientific consensus

Controlled incubation studies consistently find:

About a 50:50 sex ratio

No pattern based on egg shape, size, or appearance

Bottom line

Rounded vs. pointed eggs = myth

There’s no visual way to tell a chick’s sex from the outside of an egg

There are loads of old poultry “rules” people swear by—but almost all of them fall into the same category as egg shape: interesting folklore, not reliable biology. Here’s a clear breakdown.

Old wives’ tales about chick sex

Egg appearance myths

Pointed egg = male / round egg = female

Large eggs = males / small eggs = females

Rough shell = cockerel / smooth shell = pullet

Darker shells = one sex, lighter = the other

None of these have any proven link to sex.

Candling (looking inside the egg)

People claim you can tell by:

Air cell size or position

Vein patterns

Dark spot placement

In reality, candling shows development and health, not sex.

Egg position / incubation tricks

Pointy end up vs. down changes sex

Turning eggs more/less changes sex

Temperature tweaks produce more males or females

These don’t change sex. Poor incubation might kill embryos—but won’t switch sex.

Timing & superstition

Laid during a full moon = more females

Certain days of the week give certain sexes

First eggs of a clutch = males

Pure folklore—no biological mechanism behind them.

The “swing test”

Tie the egg to a string and:

If it swings in a circle → female

If it swings back and forth → male

This is basically like a pendulum—movement comes from your hand, not the egg.

Float test (in water)

Eggs that float a certain way = male or female

Floating only tells you freshness, not sex.

What’s actually true (beyond what we’ve covered)

1. Sex is genetically fixed (but with a twist)

Hens are ZW, males are ZZ

The hen determines the sex before the egg is laid

That part is solid science.

2. Slight sex ratio skews can happen

While you can’t control sex from the outside, research suggests:

Hen condition (nutrition, stress, age) may slightly bias ratios

Some studies show healthier hens may produce marginally more males

But:

Effects are small and inconsistent

Nowhere near reliable enough to predict or control outcomes

3. Incubation affects survival, not sex

Different conditions may cause male and female embryos to survive differently

For example, one sex might be slightly more sensitive to:

Temperature extremes

Humidity issues

This can shift the ratio of hatched chicks, but:

It’s indirect (via survival, not determination)

Not predictable enough for practical use

4. There are real ways to know sex before hatch (but not by eye)

In commercial settings:

In-ovo sexing (inside the egg before hatch):

Hormone or DNA testing

Spectroscopy / laser scanning

Used in large hatcheries to avoid raising unwanted males (especially in egg-laying breeds)

Breed-specific genetics:

Some breeds are auto-sexing

Chicks hatch with different colours depending on sex

Others are sex-linked crosses

Males and females have different down patterns at hatch

But you still can’t tell just by looking at the egg itself.

Bottom line

Old wives’ tales = fun but unreliable

Egg shape, size, colour, and handling do not determine sex

Sex is fixed genetically before laying

Only scientific methods or specific breeding genetics can reveal it early