Pigeons being preyed on by other animals.

You have got to check out this story from IO9.

Quite honestly I never considered why big cities have millions (or so it seems) of pigeons but you never see a dead one lying around.  Now we know.  Predation.  Reading the comments, people were surprised that pelicans would eat pigeons.  They shouldn't have been.  Pelicans will eat almost anything that will fit down its gullet.  Snakes, frogs, stray cats, small dogs...the list goes one.  Some people need to get to the great outdoors and learn the ways of the natural world.