Jackdaws are big trickster animals. They are highly agile and can easily outmaneuver a pigeon, and easily snatch a delicious nut away with a few hops and flaps. However, they can't peck, and with their large beaks cannot access smaller leftovers accessible to pigeons. This is often what is underestimated about the pigeon. They are fast, accurate peckers, and will leave nothing behind. They do indeed occupy a niche, and are highly adapted to procure food on the street, unreachable to other animals.