We all know that birds don't have teeth but those spiky things in this shoveler's bill are called lamellae. Shovelers feed by swimming along with their bills (and sometimes their heads) submerged and the lamellae are for filtering small creatures out of the water - a bit like some whales do.
This photo was taken by Nigel Blake and is one of thousands you can find on our RSPB Images library. Have a look!