I found this old thread when I was searching for info on controlling the sex of chicks through temperature or other manipulation. I was going to start a new thread with the links I found but instead will just copy them over here.
I had a thought that maybe you could control the sex of your chicks by some different techniques that would result in say more boys that girls at hatch or vice versa, so have googled it and found some interesting articles out there so I though I'd post them here for others to find.
http://ps.fass.org/content/90/10/2402.full This one is a study on quail and one of the interesting bits in it is that the age of the grandparents when the parental eggs were gathered might have an effect on the numbers of each sex in the second generation.
http://sciencefocus.com/qa/can-chickens-really-change-gender this one gives no references but suggests that cooling eggs after laying for 3 days increases the number of egg laying, functional, female appearing chickens, even tho their chromosomes are male.
http://www.news.cornell.edu/stories/May05/birds.gender.ssl.html Not of practical use to back yard breeders but some evidence that it's the hormone levels of the hen that determines ratios of male:female in offspring
My Edible Garden http://edible-garden.blogspot.com/ Current bird count; about 40 + or - a few chickens, 7 ducks; Easter Eggers, Olive eggers, Buff Orpingtons, Ameraucana, Black Copper Marans, Buff Plymouth Rocks, Muscovy and Welsh Harlequin ducks.