The black feathers on the back of its head and neck form a crest which is raised in a dispute over fishing rights.
This is Thomas Bewick's engraving of a bittern from his 1804 History of British Birds, showing its crest and a few of its many local names.
The bittern's scientific name is Botaurus stellaris, meaning starry bull, a reference to the booming sound made by males in the springtime and their (starry) speckled plumage.
There are over 100 pairs in the UK in the summer and several times that number in the winter. Our local birds are winter visitors and (so far) don't breed here.
Bitterns are on the red list in the UK but are less rare than they used to be, mainly as a result of attempts to provide them with a better habitat. These maps from the Bird Atlas shows the current UK distribution.
And this map shows the relative increase in the winter population.
You can listen to Kate Humble's BBC Radio 4 Tweet of the Day on the bittern here.