Header image scrolls

In your wordpress dashboard, go to Appearance -> Editor. From the list of files on the right, select your stylesheet (style.css)

Inside that file, you will need to change this code on line 897

Change from this

#featured {
    background-attachment: fixed;
    background-image: url("images/home_banner.jpg");
    background-position: center top;
    background-repeat: no-repeat;
    display: block;
    height: 380px;
    text-align: center;
}

To this

#featured {
    background-attachment: scroll;
    background-image: url("images/home_banner.jpg");
    background-position: center top;
    background-repeat: no-repeat;
    display: block;
    height: 380px;
    text-align: center;
}

You can see, the only edit is changing the background-attachment: from ‘fixed’ to ‘scroll’.
This will alter the position of your background a bit, so you may have to edit & re-upload the background image.