What gender and age groups typically respond to a mail survey?

I am writing up survey results for a community survey done by a park and recreation agency. A couple of the Board members may say that the results are not representative of the population because the ages and gender of the respondents don%26#039;t match community demographics (e.g. 48% of the population is female, but females comprise 65% of those who answered the survey). Age brackets of respondents also do not match known local demographics. I believe that certain demographic groups are more likely to respond to a survey than others. But I could be accused of stereotyping if I said in public that retired people with time on their hands might be more likely to respond. Is there any known research that confirms survey respondent profiles? Thank you!|||Females b/c i%26#039;m a guy and i hate mail surveys. but my female friends always send them to me and say they filled it out so i need to, but i never do.|||w/f senior citizen...