Header Background Image Responsive issue

Hello

I have used some custom CSS to add a background image to the header.
However when reducing the screen size the header area is incorrect size.
Please help.

Here is the code:

#header {
background-image: url(‘http://chickenempire.com.au/wp-content/uploads/2015/03/chicken-empire-header-bg4.jpg’);
background-repeat: no-repeat;
background-position: center center;
background-size: cover;
margin-top: -40px;
margin-left: -30px;
padding-left: 30px;
padding: 40px;
margin-right: -30px;
overflow:hidden;
}

URL: http://chickenempire.com.au

Thanks
Aaron