...why do male cycle commuters outnumber females?
Oddly the well publicised bike counts down here don't seem to be quite so free with their results.

I did a bit of counting back in 2001 and got about 20% female cyclists. Fewer on major roads, more on bike paths. 1300 cyclists over 3 months in a perimeter count (because the official stats only counted 5 major entry points). Interestingly despite the compulsory helmet law only 74% wore helmets (I didn't count "helmet on handlebars" as wearing a helmet).

In Melbourne there are stats here, the "cycling to work" and "cycling in Melbourne" pdfs. First graph shows approx 25% female, and in the outer suburbs mostly under 20 years old, with a broader peak in the inner suburbs (interestingly, fewer school age kids than the suburbs)

and a second chart showing that as cycling percentage goes up so does the proportion of female cyclists - women are more likely to ride if a lot of men do.