window.addEvent('domready', function () {

    var interv = '';
    var ypos2 = 0;
    var ypos = 0;
    var isflying = 0;
    var ypos1 = 0;

    $('tweety').src = fdtweetypath + 'tweety.gif';
    if(fdtweetyel == "window"){
        window.addEvent('scroll', function(){
            flying();
        });
    } else {
        $(fdtweetyel).addEvent('scroll', function(){
            flying();
        });
    }

    function flying(){
        if (isflying == 0) {
            if(fdtweetyel == "window") {
                ypos = document.documentElement.scrollTop;
            } else {
                ypos = $(fdtweetyel).scrollTop;
            }
            var tweety = $('fdinnertweet');
            var tweetMorph = new Fx.Morph(tweety);
            tweetMorph.start({'margin-top': 0});
            $('tweety').setStyles({'margin-top': 0, 'margin-left': 5});
            $('tweety').src = fdtweetypath + 'tweety_anim.gif';
            isflying = 1;
            ypos1 = ypos;
            interv = window.setInterval("checkflying()", 1000);
        }
    }

    checkflying = function () {
        if(fdtweetyel == "window") {
            ypos2 = document.documentElement.scrollTop;
        } else {
            ypos2 = $(fdtweetyel).scrollTop;
        }
        if (ypos1 == ypos2){
            var tweety = $('fdinnertweet');
            var tweetyMorph = new Fx.Morph(tweety);
            tweetyMorph.start({'margin-top': 23}).chain( function (){
                $('tweety').src = fdtweetypath + 'tweety.gif';
                $('tweety').setStyles({'margin-top': 0, 'margin-left': 5});
            });
            window.clearInterval(interv);
            isflying = 0;
        } else {
            if(fdtweetyel == "window") {
                ypos1 = document.documentElement.scrollTop;
            } else {
                ypos1 = $(fdtweetyel).scrollTop;
            }
        }
    }
});