Miért nem működik a javascriptem?

<script type="text/javascript">

function birdSong(){

var $cage = $('#cage');

if($cage.get(0).paused === false){

$('#bird-song img').attr('src', images/default/madar_play.png');

$cage.trigger("pause");

}else{

$('#bird-song img').attr('src', 'images/default/madar_pause.png');

$cage.trigger("play");

}

}

$(function(){

$.ajax('/ajax/birdsong').done(function(response){

if(response === '1'){

birdSong();

}

});

</script>