I have dwelt upon these facts because I believe that our appreciation of the general lines and of the laws regulating the great annual migrations can be very greatly assisted by the study of individual species on their migration, and good opportunities are in this report afforded us of doing so by the records of several species. One more remark:—It seems also worthy of note that very possibly these Wagtails were finding their way across Scotland from the Solway or the Clyde, and, resting on the General Post Office buildings, repaired south for daily food—as I have noticed birds do during the spring migration on the Petchora, at Ust Zylma, and Habarika, in N. E. Russia; and on the advent of a more favourable temperature and change of wind, pursued their course northward. If these are correctly recorded as Pied Wagtails,—as there is no reason to suppose is not so,—then their destination would be the North of Scotland; but if they were the White Wagtail or continental form, then, as far as general records of migration guide us, they would probably shoot off again at Isle of May or Bell Rock—towards the Continent. Mr. Agnew's note of "very white Wagtails" at Isle of May should be borne in mind in this connection (antea, p. 12).
That a line of migration does occur across Scotland both in spring and autumn between Forth and Clyde, I think, needs little demonstration beyond what we have already stated in previous reports; both from data and by referring to General Remarks this seems perfectly obvious. The evidences of the sea having at one time advanced inland a long distance past the very spot in which I now live can scarcely be gainsaid; and Forth and Clyde—by two separate branches—must at one time have approached one another very much more closely than they now do, and a comparatively narrow isthmus have been formed by at least one of these two branches. As already remarked, it is curious to find rare American and rare eastern species occurring so frequently at localities on that line; witness as the latest record of importance that of the Pectoral Sandpiper, Tringa maculata, Vieillot, at Loch Lomond, after continuous and scarcely failing easterly winds, on Nov. 24th, 1882.
Sir Geo. Leith Buchanan informs me that he believes that the wind was north-west at the time he shot the Pectoral Sandpiper, but this was local, as prevailing winds were easterly at that time. Sir George also tells me of the other birds of rare occurrence which he has met with at the same locality, but no notes at the time were taken of wind. These are as follows:—
"Buonapartian Gull, in April 1851 or 1852. Black-tailed Godwit, April, about same date. Shoveller found breeding, and two since shot by keeper. Two Wood Sandpipers, one in August and the other on Oct. 4th. One Little Stint in October, seen in company with two others. The Spotted Crake must breed, as every autumn I meet with them when Snipe-shooting. The Shrike I obtained once in December, 1866, and I saw another two or three winters since." I think if we thus endeavour to group together rare occurrences, and collect lists from various localities, we cannot fail to arrive at some conclusions regarding the highways of migration. We are thus working from data up to facts, without an undue amount of theorising.
It is well known to naturalists that Swallows cross the Alps by certain passes, as is also done by other species, regularly year after year. People have often marvelled at the punctuality of appearance of the Swallow and other species at certain favourite resorts. There is nothing marvellous in it. When the great general movement takes place, and the flights of birds pass over old frequented and well-known spots, these are recognised and promptly occupied by the hereditary occupants, or, if found unoccupied by later migrants, they are then filled up. This remark applies both in spring and autumn. In a former Report I have instanced the arrivals of Wood Pigeons on the Fife coast, and I have also instanced breeding-sites of birds occupied for many years, unoccupied for two or more years, and then reoccupied again. I am informed by Mr. A. B. Herbert that some of the favourite alpine passes for the annual migration of birds are the Albula and Bermina Passes into the Adda Valley and Lake Como, returning the same way in spring. If this regularity occurs during the passage of the bulk of migratory birds, I think there are good reasons for believing that a similar regularity appears in the distribution along certain lines of rare visitants, even if travelled all the way from America or the Asiatic steppes and tundras. No doubt they get into the groove—so to speak—and carry on in company with the main flocks of other species, joining issue with them along the great highways of migration, which I think have been well pointed out in many cases by Palmén and Herr Weissmann. Though the article by the latter has been abundantly criticised and even pooh-poohed, I venture to record my firm belief that there is more in it than appeared on the surface, and that the more we know of migration the more fully will his theory be borne out.
It is known to naturalists that some species which are known to breed in the highest northern latitudes travel on migration to the furthest southern localities. Let us instance the Knot (Tringa canuta). Temperature has to do with this directly. What a vast breeding-ground of this species, as yet undiscovered, must there be somewhere in the far north if we witness the great streams on their annual migration along our coasts. In spring they travel on and on towards the north until they find a temperature cool enough for the successful hatching and rearing of their young, reaching their far off summer quarters even before insect-life has begun to show itself, after the long Arctic winter; and, with the strength and vigour of a far northern-bred species, they adapt themselves to the only food existing—the fronds of lichen laid bare by the first melting of the snow. The hardiness of the race, bred thus on the shores of the Arctic seas, induces the vigour and "fitness" which enables them to travel so far again to the southward in autumn and winter; and it is the annual overflow of their vast numbers, pressing behind those in the van, which—as it were—adds impulse to the ability, and carries them forward. They press forward in autumn to fresh feeding-grounds as those behind are taken up by others succeeding them.
The Report for the West Coast of England, although frequently applied for by the Secretary, has up to this date not been received.
August 26th, 1883.
IRISH COAST.
In the spring of 1882 forty schedules were forwarded to the light-keepers, and in the autumn forty-one. Thirty-one stations returned answers in the spring, and thirty-two in the autumn.