All that is being discovered is that sons mean more grandchildren, and a few groups (billionaires, top-ranking wives) are cherry-picked because they have more sons. Dung flies are mentioned but they are not even mammals, and they aren't sex selecting their sperm.

That said, though the article claims a mechanism is unknown, diet can influence whether a girl or boy is conceived:

http://genderdreaming.com/2011/05/the-french-gender-diet/

http://www.rbmojournal.com/article/S1472-6483(10)00549-3/abs...

My own wild guess is that the observed diet factors, or at least certain states of the body that diet can cause, account for any statistically significant distributions of sex, not a mysterious sperm-guiding mechanism.

Or, perhaps better, here: http://med.stanford.edu/ism/2013/july/ratios.html -- this being where ScienceDaily copied it from. (There's actually a tiny bit of extra information in the Stanford version, namely its last sentence.)

Or here: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjourna... -- this is the journal article it's all about, and reports the research in much more detail.