Strange object in 911 Video

6 Frames in less than one second of this video:
http://www.garagetv.be/videogalerij/bartvanbelle/unseen_footage_9_11.aspx

What is that? Starts in the upper left hand corner. Whatever it is, is moving very fast. I have seen these things cast shadows on the WTC towers equal in size to the thing casting it, so these things are not birds. This thing appears at the 8:24 Mark in the video, don't blink or you will miss it.
More details and photos on this page:
http://www.v911t.org/bird.php