I see them at times between Wells and Cley on the saltmarsh and up the Stiffkey Valley. They can be a problem if you have breeding birds about. They caused a complete gull\avocet\oystercatcher\LRPs breeding failure ( about 80 nests ) at one site 3 years ago. They never killed any birds , but seemed to want to play marbles with the eggs. The next morning there were eggs scattered all over the nesting islands and in the water with otter tracks all around them.