What is the rarest bird you've seen? In Britain could it be Allen's Gallinule, or Brown-headed Cowbird, or maybe on a world scale you've managed to see Carunculated Fruit Dove, Djibouti Francolin or Eaton's Pintail?
You can now check your top 100 'blockers', that is species you have seen that very few other listers have. On any list, click the kiwi to get a list of up to 100 blockers, ordered by their rarity value. You can do this for any list for any other lister too, not just your own lists.