Anyone know how to creatthis effect?

I am sure the COW is where I saw a demo tutorial of this, done in aftereffects, it involved footage of a marsh bird flying out of frame toeards the horizon. The demonstrator first motion-tracked the footage, then grabbed stills along the track and used a multipoint garbage mask to rotoscope the individual stills over the moving video layer below. By adding a decay rate to the opacity of these stills, he got a nice stream of still trails that faded a few wing beats behind the bird.

But for the life of me I can't remember where I saw this demo, or who did it, or the title.

Hi Sean, just read this thread. Could you please post the URL of the tutorial you found for this effect?

Thanks,

--Joe