Single  mums are  better at  raising their  kids than parent--at least in the  bird  world.Mother zabra  finches have to work harder and raise  fewer  chicks  on  their own ,but  they  also  produce more  attractive  sons  who are more likely to get  a mate.

    The  finding  show  that family  conflict is  as important an   evolutionnary  driving  force  as ecological  factor  such as hunting and food  supply.