Problem with site menu on mobile

Site: www.fadsmenomoneefalls.com

When the site is viewed on a mobile phone (reproduced on Nexus 4 and iPhone 3, 4 and 4S) the responsive CSS causes the top menu bar to be displayed vertically, with parent and child menu options visible. When viewed on a mobile phone, only the child entries are 'clickable' (touchable?), so for example the Contact Us link doesn't do anything.

When resizing the browser window in Chrome or Firefox, the parent links ARE clickable.

Any ideas why there is a problem when viewed on a mobile?

Thanks in Advance

Steve