Challenge: create traces from birds footage

Hi!

I have an idea for a video involving footage manipulation that I know how to make manually in PremierePro, but it is very time-consuming. I've always wanted to learn how to program in Processing and I thought this might be a good opportunity to get started. I'm a complete beginner so be kind there :)

Essentially what I would like to do is to get a piece of footage (say shot in 25 frames per second), extract each frame into a still picture and overlay with a blending mode of Lighten. The final effect is that you see moving objects in the shot creating traces.
Any pointer to how I may go about doing this?

By the way, any suggestions of tutorial to learn how to manipulate footage in Processing is much welcome!

Cheers,
Diego