One of the most familiar examples of a northern British bird is the Red Grouse (_Lagopus scoticus_). By most authorities it is looked upon as a species distinct from the Scandinavian Willow Grouse (_Lagopus albus_), but except in colour it is indistinguishable from it, and the eggs are identical. The whole genus _Lagopus_ is a distinctly Arctic one, and there can be no doubt that the British Grouse belongs to the northern migration, just like the Arctic Hare. The Ptarmigan (_Lagopus mutus_) and the Snow Bunting are also migrants from the north. Though as resident British birds they are quite confined to Scotland, the remains of the former have been found in a cave in the south of Ireland, showing that its range in the British Islands was formerly more extensive. Another bird which probably came to our shores with this same migration, though it is now unfortunately extinct, is the Great Auk (_Alca impennis_), of which some specimens have luckily been preserved in our museums. From the occurrence of its remains in kitchen-middens and other recent deposits, the Great Auk is known to have inhabited the coasts of Scotland, Ireland, and Scandinavia, as well as those of Newfoundland. Mr. Ussher recently found the bones of this bird near Waterford, which, I believe, is the most southern locality known. The manner of their occurrence leaves no doubt that the bird had been used as food by the early races of man. In all probability it originated in the Arctic Regions, and subsequently spread south on either side of the Atlantic. We need not here refer to the many winter visitants,--northern birds which appear regularly, or at more or less long intervals, in these islands,--although in most of the ornithological works they are included under the term "British Birds."
All the British reptiles and amphibia appear to have reached us from the south or east, but among the fishes there are a good many northern forms. The whole salmon family--the _Salmonidæ_--are typical northern immigrants. The Stickleback (_Gasterosteus aculeatus_), too, has undoubtedly come to us from the north. The genus _Cottus_, like _Gasterosteus_, is certainly Arctic in origin. Originally freshwater forms, many species are now found between tide-marks, and of these a few have migrated southward along the coasts of the great continents. Thus we meet with various species of _Cottus_ as far south as California and Japan, on the American and Asiatic coasts of the Pacific respectively. In Europe, two species, viz., _C. scorpio_ and _C. bubalis_, range as far south as the French coast. Our freshwater _Cottus_, the Miller's thumb (_Cottus gobio_), has migrated to us from the north with the Arctic species. All the freshwater forms, indeed, of this genus are typically Arctic.