I volunteer at my local RSPB reserve.
It doesn’t take a genius to work out that, during weekdays, the overwhelming majority are post retirement age. My personal experience is that, on both the full days and/or the afternoons I volunteer the mixture of genders is roughly 70:30 men:women.
On Sundays, although I don’t do many, the gender split edges more toward 60:40 due to Mum & Dad or Grandma & Grandpa bringing little ones with them - not all are necessarily birders. Sundays show a marked change in the age profile with all ages ranges represented.