Aussie Finch Forum

Dumb question? I have been told that with pigeons if you have two young in a nest they will almost invariably be a male and a female. Can someone please explain the genetics surrounding this one.

Urban myth . .

Do pigeons which only lay a single egg go . . boy/ girl/ boy/ girl

Yes I think most Doves and Pigeons that have 2 chicks are 1 male and 1 female.All the Doves and Pigeons I have are 1 male and and 1 female chick always.

Hence the term "pigeon pair". Eclectus are apparently similar.

finches247 wrote:Yes I think most Doves and Pigeons that have 2 chicks are 1 male and 1 female.All the Doves and Pigeons I have are 1 male and and 1 female chick always.

Thats quite true Henry but not in all cases,thats why the old saying of having a pigeon pair comes from.I have a mate that breeds Spinifex pigeons,out of the two eggs they are mostly cocks but he believes it's something to do with the temperature of when they breed. Craig

Yes If only 1 chick is hatched out of 2 eggs I always have hens raised only.I do agree on temperature too.But Pigeons that lay one egg is luck of sexes.

Arthur, my Bleeding hearts and PNG ground doves always lay two eggs (Ok maybe once or twice a year a single egg clutch). I recently had all my BHP's DNA sexed from all of last seasons young, 50% males and 50% females (yeah for me for making up unrelated pairs).

I recently bought a "pair" of spinifex as well from the one clutch and had them DNA'ed, turns out to be Male and Female.

Urban Myth or coincidence? - I think not!!

As for Temp controlling sexes in spinifex, I remain to be convinced, yes this happens in reptiles (males cooler and females warmer - generally). While birds have evolved from reptiles they also incubate to keep them at a constant temperature - not controlled by environment as in reptiles.

I still don't understand the genetics behind this or if there is some way it can be controlled - has anyone looked into it or know the controlling factors - genetically speaking.

In birds, the female carries the unique sex gene. By convention it is called W, so males are ZZ and females ZW.
Consequently it is the ovum (egg) that determines the sex of the chick, which means theoretically the hen has the capacity to control the sex of the young.
Once the egg is fertilized the sex can not change, so external factors should not interfere unless the survival of one of the sexes is affected.

Fish are very different, and genetically have the capacity to be either sex. There are many examples of individual fish changing sex and environmental factors have a marked impact on sex ratios.

Cheers
Brett

Brett is spot on. The process of selective maturation of follicles destined to become male or females isn't fully understood but appears to mediated by steroidal hormones circulating in the mother. The process is investigated in pigeons in the following paper:

Goerlich-Jansson, V.C.; Müller, M.S.; Groothuis, T.G.G. (2013) Manipulation of Primary Sex Ratio in Birds: Lessons from the Homing Pigeon (Columba livia domestica). Integrative & Comparative Biology. doi: 10.1093/icb/ict056

Brett/Greg,
OK I am happy in the knowledge that the selective sex gene is essentially opposite to humans (as is their red and white blood cells wrt nucleus) and that once the ovum is fertilized it cant be changed - I get that. What is not clear is how two ovum maturing approx 1-2 days apart are fertilized so selectively so as to render one female and one male almost 100% of the time. If indeed it is through hormonal control only, can the hormones in the female be ramped up/down within such a small period of time to bring on the release of male or female ova only. If so has anyone done a study to determine if the first egg laid or second egg laid is male or female following this convention - ie is there a preferential pattern. IE if only a single egg is laid in a species that normally produces two in a clutch will a single be always male or female?
There has to be an answer????