Will the sex ratio of chickens become favourable to females?
Any chick has a mother and a father. Hence, the contribution to the gene pool of the following generation comes at 50% from males and at 50% from females. As a result there is no selection for biasing the sex-ratio among its offsprings. The variance in reproductive success might be higher among males than among females but that does not matter for the sex-ratio.

This is known as Fisher's principle. In the terms of W.D. Hamilton (Extraordinary sex ratios), copy-pasted from wikipedia:


  [..] given the condition that males and females cost equal amounts to
  produce:
  
  
  Suppose male births are less common than female.
  A newborn male then has better mating prospects than a newborn female, and therefore can expect to have more offspring.
  Therefore parents genetically disposed to produce males tend to have more than average numbers of grandchildren born to them.
  Therefore the genes for male-producing tendencies spread, and male births become more common.
  As the 1:1 sex ratio is approached, the advantage associated with producing males dies away.
  The same reasoning holds if females are substituted for males throughout. Therefore 1:1 is the equilibrium ratio.
  


To my knowledge, only kin/group selection can yield a sex-ratio different from 1:1 to be an ESS.