Behavior and Look of Menus with small screen resolutions

When the screen width is reduced to the point where a horizontal menu collapses into a drop down list, the behavior of the drop down list is a bit strange: It displays ‘Secondary Menu’ (that’s what I’m using for the menu), and clicking on it does not open the drop down, but navigates down to the bottom of the page where a series of links to the menu items show up in a vertical list. Is this the expected behavior?