Puffin Island
Just off the North Wales Coast is as it's name suggests, a haven for the beautiful and resident seabird, the dainty Puffin. I've sailed these waters with friends over consecutive summers and often moored up for the night on the quiet side and I only ever saw 2 Puffins.
Rats
When I asked the local Harbour master at Conwy where the Puffins had gone, he told me they had been trying for the last few years to eradicate Rats which had inadvertently been brought to the Island many years ago. As you can imagine, rats on an island would feast on bird eggs given half a chance and so Puffins had given up nesting there long ago. Apparently the rats have now all gone (hopefully) and Puffins will slowly return when they forget about rodents.