Hatch rates; male/female ratio

There is really no way to tell what will be what. Ultimately it depends on the breed and from what stock they're from.

I have hatched Cochins this year with a high male rate but I have also hatched some light sussex with every single one being female!

It's just pot luck :-)

Is the male/female ratio related to incubation temperature at all (like it is in reptiles)?

Now that would be interesting to find out! My last batch were 2 male 6 female and the temperature went up quite a bit on Day 20 (was in the sunshine and went up to 40c !!!) This time I've kept the temperature very slightly lower but I don't know what sex they are yet

I was told the chances of girls is improved the later in the hens laying season the eggs are set... we will see.

6 Dec 08 hatch 3 boys 6 girls
25Dec 08 hatch 5 boys 3 girls (the miracle chicks!)
24 Jan 09 hatch 2 boys (1 Maran, 1 Orp)
18 Feb 09 hatched Dorks 2 boys 4 girls
hatched Orps 2 boys 2 girls
hatched Marans 3 boys 3 girls

If you scratch any meaning from this do let me know!

I did hear that in birds its the male that tougher at birth (in mamals its generally the female has more get up and go) and apparently the male has the matching chromosome too ie XX.. has anyone else heard this?

Not hatching any this year but last year hatched 2 clutches the first 3 male and 5 female that was June and the second clutch in August was 6 males and 3 female, no logic. I think that it is the luck of the draw.

Only hatching Quail this year and they are for the pot so it doesn't matter what sex they are.

I commented on this on the other thread.
I believe that if the temp (or humidity or anything else) is a bit 'off target' one gender is more likely to survive. I suspect which gender will die depends on exactly how the conditions vary from ideal.
It might be worth trying to correlate whether variation from 'close to 50:50' tends to happen when hatch rate is low, but the smaller the clutch, the less reliance you can place on actual figures anyway. If you get all males in a clutch of 4, that is likely to be co-incidence. If you get 75 males in a incubator hatch of 100, that is likely to be significant of SOMETHING (but of what is less readily determined). If there were 150 eggs, and only 100 hatched, of which 75 were males, then something is probably killing off females 'in shell'.

Corax, it is true that in birds it is the male who is the homozygous sex (XX, though in this case I think it's called MM). Every fertilization though is an independent occurence. This means that, for example, although OH and I have brown eyes we both carry a blue eye gene from a blue eyed parent, this gives us a 1 in 4 chance of having a blue eyed child. If we have 3 kids with brown eyes it doesn't mean the 4th will have blue ones, it will still have a 1 in 4 chance. With gender the odds are 50:50, but because fertilization is random you'd need to sample a huge number before you reach these figures. I know of one family who have 5 girls and another who, when you count children from former marriages, has 9 boys to one girl, neither is indicative of the population as a whole, even when taken together. I suspect that we hatch such small numbers ourselves that even if we pool our resources we would be unable to come up with anything useful statistically. Hatching at different temperatures might be interesting, though I think it's more down to survivability rather than anything truly affecting the gender ratios. There are a fair few diseases of humans which are sex linked, (the female is the carrier, but only the male is affected because females, being homozygous, have 2 copies of the gene and therefore a good chance of having an unaffected copy) think of haemophyllia and colour-blindness, which tend to only affect boys. As the situation is reversed in chickens it may mean that the hens are developing something similar, though I've never heard of it.

Thanks for all your replies. I'm particularly interested in your comments Hilary, Corax and Bluemoon about a possible gender related "weakness", as I've lost a higher than normal amount of Welsummer LF chicks pre-hatch (ie dead in shell) this year compared to previous years and I've been wondering if these are females. I'm using a new Welsummer cock (although a home hatched one, not bought in) and his fertility rate is good (virtually all eggs are developing, hardly any "clear"). All the Welsummer chicks hatched so far are cocks, with one possible female.

But, on the bantam side, although I'm not getting any dead in shells, still the amount of cocks to hens is high.

I incubate using a combination of broody and incubator, and all the bantam eggs have hatched successfully in the incubator, but not the Welsummer, so I'm confident it's not a machine fault. (The incubator hatched chicks get stuffed under the broody to join the others when they come off.)

Certainly as far as the Welsummers are concerned I will be eating my stud cock and getting a new one in. Having said all of the above, the chicks that have hatched are strong and healthy and very vigorous.

The chicks I hatched in late Feb gave me 7 hatched from 12 set. It now appears only one is a female, possibly 2!

I have one more lot of Welsummers due off (only 4 eggs under a hen) so will see how they fare.

I hope to get a better balance though with my bought in Cream Legbar eggs. Watch this space!!

If Cockerals carry the ZZ (I looked it up <g>) gene and female is WZ surely its the hen which will provide the chromosome that determines the gender (following the reversal of mammal genetics where the sperm provide either X or Y)? Stud cockeral wouldn't have a girl chromosome so wouldn't be at fault - I guess then and egg can carry W or Z... ?

Another thought - although hardly scientific the times my haches were heavily male co-incided with the times I know the incubator suffered a crisis (when I got the two boys for example (from 15 eggs) and nothing else the cradle pushed open and the incubator dropped (with a bump) -twice because by attempt at prevention failed first time. The Christmas day chicks suffered significant power cuts - one night being kept warm by the coal fire and another shipped out to the car with a gadget to convert the power my poor little car was on tick over all night long and I got up every hour to check nothing was over heating (long night)!
The large group did also have a crisis - as documented on here a powercut in the morning where the incubator dropped to below 12C but after some investigation the power was found to have only been off for 1hr ish ...
Anyway I fully accept this is purely anecdotal but interesting just the same...

Never was much good at algebra and you've lost me completely.
One interesting thing I found out lately (and appologies that it's totally unrelated to the original thread title)........... is that in a blue Aruacana the blue egg laying gene is carried with the male? If I can possibly rellieve a fellow allotmenteer of his L/F blue Arucana cockerel I could put him with ANY hen and hatch chicks that lay BLUE eggs.......I think?

If all egg colour is carried by the male of the breed I think so too- except I saw picture somewhere of Olive green caused by crossing a blue layer and I think maran (but can't remember for certain......)

What I was saying above was basically If birds are the opposite to mammals in who has the gender selection genes then Richmond will need to eat his hens rather than his cockeral