• A http://www.youtube.com/watch?v=KtT93tNJv3I&feature=related.
  
• http://www.eatmyyard.com/media/blogs/a/possum.jpg and http://rickthegreat.files.wordpress.com/2010/03/raccoon-wbg.jpg that only come out at night.
  
• Pigeons in the cities and http://image55.webshots.com/155/4/38/15/457943815ygbvhl_ph.jpg.

gothemasticator

Same here ....and also:
Leaves falling off trees (in a way you already said that though)...

Or changing the ground cover to snow when it snows in the winter months.