Water Rail (Rallus aquaticus)
The secretive bird is often viewed for just a few seconds dashing from place to place through the densely vegetated wet places where they live. They are often easier to see in the winter where cold weather pushes them out, this is especially true when the ground is iced over. The second photograph in the slide show was taken in the winter when many of the lakes at Ham Wall RSPB reserve on the Somerset levels were frozen.
If you see the this bird you will need a fast shutter speed and quick reactions as you are unlikely to see if for more than a few seconds.