Why is a duck tapping on my window?

We put this to Eleanor Drinkwater, from the University of Cambridge...

Eleanor - Well it's a really difficult thing to say without seeing the ducks themselves but I'd say it could be down to two things. One if there was a nice reflections of a duck on the other side. Ducks can't recognise their own reflection. The only bird known to recognise their own reflection is, actually, magpies, so it could be thinking there's another duck there.

Alternatively, if you've ever fed it before, it could be coming back to try and check out the scope and try and persuade you to feed it something else.

Kat - Has anyone noticed this with ducks - has anyone got ducks in their garden?

Giles - Because I was asking you, I think, before we came in here whether it's the same reason as with crows? Because we had this crow on the top of our house once just tapping at he window and we had to put these little spiky things up to stop them from actually coming in.

Chris - I think Eleanor's point about the reflection is the one because our next door neighbour has a window that, at certain times of the day, it reflects the sun and the birds sit on the window sill and tap on that round window. And, I think, if you look I can see a reflected bird sitting and I think they probably catch sight of themselves as they go past because birds have got fiercely good vision, haven't they, Eleanor?

Eleanor - Yes.

Chris - And so they're probably trying to attract this predator that's invading their patch.

Kat - And then there's also the reverse problem isn't there? Because my mum has big patio doors and before she put some big stickers of birds on them, because she used to get poor little things flying straight into the glass because they couldn't see it. Is that quite a big problem too?

Eleanor - Yes, birds flying into windows is a really big problem. And, in fact, there's some really cool research that's going on, as birds can see in UV and we can't. So there's some really cool research going on to kind of put some stripes across the windows and all sorts of different things to make marks that the birds can see that we can't.

Kat - Oh wow! So you could have like a scary UV bird that instead of obscuring your vision with a sticker?

Eleanor - Yes, well that's the idea.

Chris - I think the duck was just quackers!

Eleanor - That's the other alternative.