I don't see why a question can't relate to more than one book and incident ie: how many books feature a parrot?
Because it proved to be impossible to moderate when such questions were posed in the old trivia quiz, that’s why, leading to all sorts of problems, arguments and contentiousness.
To be honest from the top of my head I can only think of two (maybe three) books that a parrot appears in.
There’s the problem right there - “off the top of your head” isn’t good enough: and looking at the two (or three) books in which you remember seeing parrots doesn’t provide confirmation or an answer - it merely bolsters your prejudice in this matter. The only way to answer it is to go through every book, one by one, frame by frame, and look - you ask the question, you need to know
the answer. Is it two, or is it three, or four, or seven?
Does “a parrot” mean a single parrot, ruling out books with more than one parrot? What is the biological definition of a parrot? Is a stuffed parrot still “a parrot”, or is it an ex-parrot? Would a book containing a drawing of a picture of a parrot on a poster or sign, rather than a drawing of a parrot count? If there is a street called “Parrot Street” but no bird, does that book count? Does a parakeet count? What is a parakeet? Is what Hergé drew a parrot or not? Is that blob on the branch in the background of frame x on page y a parrot or not?
What happens when you say “five” someone else says “13”, and the answer actually is six? Chances are you’ve said “you’re a winner!” to the first person who says five too, the person who said “13” is now trying to justify their answer to say that they thought you meant how many parrots are there in the books, not how many books (chances are it says one thing in one place, and something different the next), and the bod who said six, who was right has lost their turn and wasted their time…
All these things preclude easy resolution and agreement on answers. It takes no time at all to ask which books contain a parrot, and so much time and aggro to get the right answer…
So let’s keep it simple, and straight forward, and non-controversial, and have questions and answers which are simple and definitive please.
Oh, and a) I don’t actually know how many parrots there are, or b) how many books they appear in, and c) “parrot” becomes a very odd word after typing it a few times in quick succession!