- for the person asking whether it's true that pigeons always lay two eggs, one of each sex:
Almost true. The figures are based on feral pigeon research, but other species are nearly as accurate. They always lay two eggs, one day apart. In about 90% of nests, there will be one of each sex. What is really awesome though, is that in 78% of nests, the male will be the firstborn. No other species of bird comes even close to this percentage.
Apparently, the reason is that for the first 5 days or so, the male chick is stronger than the female. The eggs hatch 18 days after they are laid. It's always possible that in between the laying and the hatching, the weather or food supply might have changed significantly, and if it is only possible to raise one of the chicks, then the male is more likely to survive difficult circumstances. By 5 days though, the chicks are equal in size and strength.
This is the origin of referring to children where one is male and one is female as a 'pigeon pair'
