Well, compare the family with the single bird and from now on you are in possession of the invaluable (?) knowledge that Whooper Swans have rounded tails and the Mute Swan have pointed tails, and thus you need never have a problem with swan identification again (except with the Bewick's Swan, of course - another rounded tail, though smaller!)
This may well come under the heading of "Not many people know that", not to mention being one of the top 50 facts about birds you didn't really need to know, but maybe one day it will come in useful. What about including it in a bird quiz, for example?
Of course, you have to take it on trust that I know what I am talking about :-))
Have a good Hogmanay!