How many rare birds do we miss?

As birders we often talk about the problem of common birds being misidentified as rare ones. The counterpoint, but probably more frequent, is that rare birds are simply overlooked. Here's a link to a fantastic "Awareness Test" on YouTube. 

Give it a try, it only takes a minute. The relevance of this test to bird identification should be obvious, so now you can just imagine all the rare birds you haven't seen.