How Temperature affects Sex of chicks

[eggscetera]

OK - odd question. If your incubator is off temperature a bit, is it likely that more females would hatch than males? We got an unusually high number of female chicks (yay!) and I wondered if it was because my incubator was cooler than recommended (only because I didn't notice the temp had dropped a bit). My husband thinks it's because it caused more eggs to turn into females than males. Is that possible? Can eggs originally be either sex? I guess I thought eggs themselves were either female or male and the sex was determined before the eggs went into the incubator. Any knowledgeable folks out there that can explain the science of eggs? And if temps can cause one sex or another to form?

 

[Ridgerunner]

Sex is determined by the hen before she lays the egg. If you read up on sex links, you’ll find that the hen gives a copy of all genes to her sons but withholds the sex linked gens from her daughters. Which set of genes the hen contributes determines sex.

If temperature could change sex, all Cornish Cross chicks that hatched would be male. They grow faster. Every chick that hatched for egg laying operations would be female. It does not happen that way.

The individual odds on each egg is 50-50 male or female. That does not mean half you hatch will be male and half will be female. It’s pretty normal with my hatches that they are about 2/3 of one sex, sometimes 2/3 female and sometimes 2/3 male. Pure luck.

Where that comes from is from some reptiles. Incubation temperature of certain reptile eggs will affect the sex of the offspring, but not with chickens.

 

[eggscetera]

Thanks for clearing up that little mystery Ridgerunner. I guess I was just really lucky with the incubation this time around. Although my luck is running out because we have a hawk that's killed four pullets and a hen in the last week. No more free ranging for my birds.