breeding on the rocks; we certainly saw nothing else, and no Common Terns even, except on the one island on which we found the eggs.  The autumnal visitants are mostly young birds of the year, some of them, of course, having been bred on the Islands and others merely wanderers from more distant breeding-stations.  No young Terns appeared to have flown when I left the Islands at the end of July; at least, I saw none about, though there were several adults about both Grand Havre and L’Ancresse Bay.  The same remark applies to Herm, where my last visit to the shell-beach was on the 22nd of July, when I saw several adult Common Terns about, but no young ones with them; all these were probably birds which had been robbed of one or more clutches of eggs.

Professor Ansted includes the Common Tern in his list, but only marks it as occurring in Guernsey.  There is one specimen in the Museum, a young bird of the year.

164.  ARCTIC TERN. Sterna macrura, Naumann.  French, “Hirondelle de mer arctique."[31]—­The Arctic Tern is by no means so common in the Islands as the Common Tern, and is, as far as I can make out, only an occasional autumnal visitant, and then young birds of the year most frequently occur, as I have never seen a Guernsey specimen of an adult bird.  I do not think it ever visits the Islands during the spring migration; I did not see one about the Vale in the summer of 1878, nor did Mr. Howard Saunders and myself recognise one when we visited the rocks to the north of Herm.  It may, however, have occurred more frequently than is supposed, and been mistaken for the Common Tern, so it may be as well to point out the chief distinctions:  these are the short tarsus of the Arctic Tern, which only measures 0.55 of an inch, whilst that of the Common Tern measures 0.7 of an inch; and the dark grey next to the shaft on the inner web of the primary quills of the Arctic Tern, which is much narrower than in those of the Common Tern.  These two distinctions hold good at all ages and in all states of plumage; as to fully adult birds in breeding plumage there are other distinctions, the tail of the Arctic Tern being much longer in proportion to the wing than in the Common Tern, and the bill being nearly all red instead of tipped with horn-colour.

The Arctic Tern is not included in Professor Ansted’s list, and there is no specimen at present in the Museum.

165.  BLACK TERN. Hydrochelidon nigra, Linnaeus.  French, “Guifette noire,” “Hirondelle de mer epouvantail."[32]—­The Black Tern is by no means a common visitant to the Islands, and only makes its appearance in the autumn, and then the generality of those that occur are young birds of the year.  I have one specimen of a young bird killed at the Vrangue on the 1st October, 1876.  It does not seem to occur at all on the spring migration; at least I have never heard of or seen a Channel Island specimen killed at that time of year.  As this is a marsh-breeding Tern, it is not at all to be wondered