Using an animation over top of another div loses responsiveness

Hello,

I made an animation of flying birds in Adobe Edge and then inserted into my existing HTML page (not able to open HTML in Edge as it crashes).

I want the animated birds to fly over the existing text which works great when window is full size. But when the window is smaller my existing text is no longer responsive.

I'm not too worried about the animated birds being responsive, though this is preferable, but the divs underneath needs to be.

Is this possible? Am I doing something wrong with the stage settings perhaps?

To create an overlay I have been putting the closing div for the animation after the existing div, or is there another/better way to do this.

Here is the page Box Of Birds - We Sell

Thanks in advance to anyone who can help me out!