The US d'A is well-known for doing everything slightly bigger, if not always better. And when they can't do it better, they just do it even more biggerer. That's true for fast food portions, cars, motorways, presidential candidates, and religious lunacy.
But somehow, pigeons slipped through the net. On more than one occasion I've heard American visitors to the temporarily-United Kingdom exclaim superlatives at the size of our resident pigeons, and run for the cover of picturesque Post Offices and red phone boxes.
And they are right to be fearful, for if a British pigeon doesn't catch you, you'll probably catch something from a British pigeon. Here is Beware! The Zine's handy visual guide to the North American and British pigeons: