Trouble getting data on server from FormData – Photoshop

I am having trouble uploading a picture file via AJAX.

Web:

<div>
    <form id="birdi_image_form">
        <input type="file" name="birdi_image" id="birdi_image" ></input>
    </form>

    <input type="text" name="species"></input>
    <textarea name="comments"></textarea>
</div>
<div id="debug"></div>

<script type="text/javascript">

jQuery(function($){
    $('#birdi_image').change(function(){
        var ima = new FormData($('#birdi_image_form')[0]);

        $.ajax({
            url:"/bird/bird_scripts/fu.php",
            type:"post",
            data: ima,
            processData: false,
            dataType:"text",
            success:function(data, textStatus, jqXHR) {
                $('#debug').text(data);
            }
        });
    });
});

</script>

/bird/bird_scripts/fu.php:

<?php

$imagedir = '/images';
$tmpfname = tempnam($imagedir, "b_");

echo var_dump($_POST);

if (move_uploaded_file($_FILES['birdi_image']['tmp_name'], $tmpfname)) {
  echo "File is valid, and was successfully uploaded.n";
} else {
   echo "Upload failed";
}

?>

From looking around online I was expecting to find contents in my $_FILES variable, but this is empty. Dumping out the $_POST var to the screen like in the example gives me the following. $_POST['birdi_image'] gives me NULL.

array(68) { [“——WebKitFormBoundaryYCAoI8shwgBavjJP
Content-Disposition:_form-data;_name”]=> string(339) “”birdi_image”;
filename=”test.jpg” Content-Type: image/jpeg ����JFIFdd��
ExifMMbj(1r2��i��B@’B@’Adobe Photoshop
CS2 Windows2008:06:24 11:11:48��b�g”
[“?o��(�ci��R��Μꟑ���]T��z���”]=> string(82) “���
f�zߠ����i���/��v��E~��[,�Y
�s�������1l�G����-���߿�enu'=�v�z���=?Ҳ���"
["�{��<o��ӗ�M��ysnʨo87~;l���۔�"]=> string(172) "�<��t�2~���O�S
�����t���㵺C�}E������}��I�d]c���y}#�����C,�Z��־��V��ynʿ��?�g�*����o��ٌ�.}�y����}��z����w^�]�m�u������z>�37�_C긵��K𭪣�Y-{��뺷��M���ul��Y�"
["c�yhHp����"]=> string(152)
"��[-���1�]��|�����۽Q��e���o�~��g������u�.���A��t�]�3�W�ד��b���}>�����%��K���Ѳ�3���zX��qZ��}u��sc�
���N� ^-w�7���r� ����c��=?՗δX�j" ["C�uw���-��"]=> string(57)
"���m��w��������ѩ���������k��r����m�t�62rIk���m�ߗV��}" ["�"]=>
string(384)
"!�<��B���6*�c��劷Q���uF*��U��������ď,�y{R���������E%���Q����5.��IE���N�����Ο�̿4~R��……………Upload failed.

I have uploaded files before by using a complete form submit. This is the first time I am trying to do it with AJAX. It looks like the data is getting to the server, but I can’t seem to make any sense of it from the server side. As you can see in the code I expected $_FILES['birdi_image'] to exist but it doesn’t. Am I doing something completely wrong?

Thanks