You could declare the event based on your conditions
DEMO http://jsfiddle.net/e2fc7/
var touchscreen;
if (window.matchMedia("(max-width: 300px)").matches) {
touchscreen = true;
} else {
touchscreen = false;
}
var evt = touchscreen ? 'touchstart' : 'mouseenter';
$("header").bind(evt, function () {
if ($('#expandMenu').is(':visible')) {
$('#menubar').removeClass('menu-active');
$('#switcher').removeClasse 'switcherOpen');
} else {
$('#menubar').addClass('menu-active');
$('#switcher').addClass('switcherOpen');
}
$('#expandMenu').slideToggle("fast");
});