There is great debate among bluebird enthusiasts about bluebird nestboxes. One is whether nestbox is one word or two. Personally, I think it's one, but my spellcheck apparently doesn't agree. Second is the debate about how big the whole should be. For many years, the consensus was that it should be one and a half inches in diameter, because bluebirds don't use them otherwise and because starlings and other non-bluebirds will use them instead. Debate rages, however, over whether this is correct or not, or if the hole should be bigger or smaller. You know which camp Floyd (and whoever built his nestbox) is in.