Air sac determines sex.

[HeyNeighborFarms]

I also read this pamphlet from the 20's and attempted this experiment.
I set 14 with egg cells on the side and 1 BCM egg that was so dark I could not see through.
I had 9 hatch alive and well. They are 3 days old now and I guess I will report back when we reach crowing age lol

 

[Ladybird CA]

It was 17 C (62 F) when I collected the eggs at 2:30. 3 eggs with all side air cells. I thought they would all be centered but nope.

Another surprise which is the blue food gel that had not shown up since it was placed in the BLRW's vent last week showed on her pointed eggs today. Maybe the much warmer temps caused the gel to be more liquid. This proves what I sort of suspected- that I mixed up her egg with the Columbian rock's. Her egg is SI 65.

The unmarked white egg is SI 70. The EE is SI 76. It’s more likely to be the Buff polish’s because if the same happened with the campine and food colouring there would be green on the egg.

It’s a flood in my yard due to melting snow. I did go back to check for more eggs at 5:30 but there weren’t any.

 

[TexasBlues]

Does it state numerically in that study what the shape index range is for pullets and what it is for cockerels?
I do take note when hatching eggs if they are pointy or round, but I’ve never taken measurements .
I have calipers now ($6 Amazon)so I can take measurements and calculate the shape index. If I have enough eggs next time I incubate, I could initially select only round eggs then from those eggs only select eggs w/ non-centered air sacs and see if I get higher than normal pullet avg.
It’s doubtful that it will work, but not hard to try.

 

[HeyNeighborFarms]

Does it state numerically in that study what the shape index range is for pullets and what it is for cockerels?
I do take note when hatching eggs if they are pointy or round, but I’ve never taken measurements .
I have calipers now ($6 Amazon)so I can take measurements and calculate the shape index. If I have enough eggs next time I incubate, I could initially select only round eggs then from those eggs only select eggs w/ non-centered air sacs and see if I get higher than normal pullet avg.
It’s doubtful that it will work, but not hard to try.

https://archive.org/details/howtotellsexofeg00quis/page/n1/mode/2up

Here is the link to the 1920 USDA Pamphlet we are discussing. I found it an interesting read and if nothing else a fun experiment.

 

[TexasBlues]

https://archive.org/details/howtotellsexofeg00quis/page/n1/mode/2up

Here is the link to the 1920 USDA Pamphlet we are discussing. I found it an interesting read and if nothing else a fun experiment.

Yes I did read that one and I have an understanding of Mrs Fry’s Air Sac theory. What am I asking about is the shape index study that supposedly predicted sex w/ 80% accuracy.

https://pmc.ncbi.nlm.nih.gov/articles/PMC9832119/

 

[Ladybird CA]

They did not mention that there is a range for pullets or cockerels, just that a higher percentage of pullets hatched from eggs with a higher shape index.

Today the high is 12, low 1 C. I forgot to check the weather when I gathered the eggs 2 hours ago around 5:15 PM. Right now it is 7:27 PM and 9 celcius. It was sunny earlier so all 7 hens laid again. It was a mess of yolk in the nest box that 6 of them share. The EE lays her eggs in the nest box next to the last one. She was the first to lay in the nest boxes and had always laid in that one. The egg that only had remnants of yolk left was laid by the BLRW. It must have had so much blue dye on it that it rubbed off of a white egg that is the size of the serama egg and has no yolk, as well as the Columbian rock's egg.

The 3 with side air cells:

1. Columbian Rock SI 76
2. EE SI 72
3. Serama SI 73

The 2 with centered air cells:

1. White egg with calcium spots on it 72
2. White egg 76

For some reason all the eggs are rounder today than usual. None had less than an SI of 70.

I added 2 drops yellow food gel to the golden polish's vent as there were no yellow gel on any of the white eggs despite all 3 white egg layers laying. I also mixed it with the green food gel and used a dropper to add its contents (4 drops) to the campine's vent.

I added more pine shavings to the nest box so hopefully there won't be cracked or broken eggs tomorrow. I'm not sure if the rabbits are breaking them or the hens.

 

[Ladybird CA]

Today the weather is a high of 8 C (46 F) and low of 1 C (33 F), with it being 8 C when I collected 2 polish eggs at 5:20 pm. One is a round golden laced with SI of 70, centered air cell. The other is the buff polish’s egg, the pointiest I’ve had with the lowest SI of only 53. In this case Pliny would be right that males come from pointed eggs and females from round. 2 scientific studies that I’ve become aware of state otherwise.

It is day 7 for the 6 incubator eggs and all are developing. All the air cells are viewable from each side now so the egg cell sexing does need to be done before incubation or at least before the 7th day.

 

[Ladybird CA]

Actually google does say Pliny said round is female, pointy male. Someone wrote that he said the opposite. Forgot where I read that.

 

[Ladybird CA]

Maybe they’re both correct and to get the best accuracy would be to follow shape index as well as air cell

 

[NatJ]

Actually google does say Pliny said round is female, pointy male. Someone wrote that he said the opposite. Forgot where I read that.

You can go check it for yourself.

By Pliny the Elder, Natural History, Volume 2, Book 10, Chapter 74 "The various kinds of eggs, and their nature." You can find an English translation here on Project Gutenberg: https://www.gutenberg.org/ebooks/60230

He says, "The rounder eggs are those which produce the female, the others the male."

https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0137:book=10
Here is another source. This is just Volume 2, Book 10, so you just have to scroll down to Chapter 74.

When you say "google does say," was that one of those AI summaries at the top of your search results? They are often wrong.

Edit to add: here is a statement from Google's AI:
"Pliny the Elder, in his Natural History, doesn't provide a method for determining the sex of a chicken egg before it hatches, nor does he discuss any reliable methods for sexing chicks. He focuses on the natural history of animals and plants, not on practical poultry farming techniques."

(That happens to be mostly right-- he is not much interested in practical farming techniques-- but he DOES mention sex/shape of eggs, despite what that AI says.)