In 1879 there was scarcity of birds at many important stations, such as Butt of Lewis and Monach Island, Skerryvore and Dhuheartach. In that year westerly and N.W. winds prevailed. In 1880 larger numbers were noted. In that year easterly gales and winds prevailed all through the migratory season. In 1879 migrants were scarce at the more northerly stations, being compressed by the westerly winds more towards the south, but in 1880 they reached much further north, being expanded by the following easterly gales and winds, as we have seen in treating of the east coast of Scotland this year.
The stations visited by the largest numbers of birds are the Bell Rock and Isle of May, both being stations pretty far southward, and Pentland Skerries, a more northern station. We now find also that on the west coast the stations sending fullest numerical returns are also southerly stations, and for the most part are situated south of the Firth of Clyde. Both on east and west coasts all returns coming in from north of Firth of Clyde in west, and north of Firth of Tay in east, except Pentland Skerries, report scarcity of birds as compared with last season (1880), and after November birds were unusually scarce. Writing from North Ronaldshay Mr. Tulloch tells us that birds seldom come so far north during migration, but usually trend more towards the mainland. On the west coast, at Rhu Stoir, very few birds are reported after November in most seasons, and similar reports come from Island Glass and others of the more northerly stations. The great gales from W. and S.W. during November and December made all birds scarce at Monach Island, even Eider Ducks being unusually scarce. At Skerryvore birds never struck lanterns in flocks this year, but only in scattered instances. It will thus be seen that the migratory seasons of 1879 and 1881 most closely resemble each other, as regards our Scottish coasts, whilst that of 1880 was more abnormal, owing to the easterly winds prevailing.
It would almost appear that the great rush of migrants in September on the Bell Rock, and more noticeably on Isle of May, would also account for the collection of birds at stations on the west coast south of the Firth of Clyde, as the dates tally with each other on both coasts, to see which it is only necessary to compare between them under several of the species. I have also independent reports upon the large crowds of birds seen passing south over the Solway Firth at these dates, few of which appear to have been seen north of the Firth of Clyde.[6] Rushes have not been so large, yet they are indicated with tolerable precision by the returns. The extremely regular and open winter has no doubt much to do with this, the temperature in Great Britain having been higher than for many years previous. But these throbs or rushes being distinctly traceable is owing, on the other hand, I believe, to the prevailing wind fully as much as to the severity or non-severity of the weather. Rushes are normal phenomena in the West of Europe, because westerly or north-westerly or southwesterly winds usually prevail there. Regular or more dispersed movements of birds in the West of Europe are abnormal, because easterly winds are abnormal there. In 1880 we had a spread-fan of migration, if I may so express it. In 1879 and 1881, in Scotland, we had a closed-fan of migration. The natural result of the wide-spread fan is continuous streams of migration and no rushes; that of the closed-fan great throbs and rushes, for birds prefer to travel with a beam wind and wait for favourable winds, and do not often voluntarily start on their flight with a following wind. The occurrence of the white-spotted form of Blue-throated Warbler after a succession of tremendous S.E. gales, culminating in the dreadful hurricane of Oct. 14th, clearly shows, I think, that acts of voluntary migration do not take place in following winds. This Bluethroat was caught up and borne away, nolens volens, and our Mid-Atlantic notes in 1880 show similar abnormal results from prevalence of easterly gales. It is to be regretted that we have no returns this season from Mid-Atlantic, owing to Mr. Anderson's engagements in the Mediterranean. Even total absence or perfectly negative evidence of birds in Mid-Atlantic would have given us a valuable standpoint as compared with the great mortality of 1880.[7]
[6] Mr. R. Service contributes the following:—"The severe gales retarded the migration of the shore birds during October to a great extent, causing them to "accumulate" in our district for several weeks. On October 12th I saw a twenty-acre field completely covered with Lapwings. At the same time, and for about a fortnight afterwards, the number of birds on the Solway banks was most extraordinary. The great majority of these were Bar-tailed Godwits, Oystercatchers, and Knots. Just outside the line of breakers opposite the rocks at Southerness Point, Scaups and Scoters were especially numerous, diving above the mussel beds. As they rose and fell on the crests of the heaving waves these birds formed many an interesting and beautiful group."
[7] I may mention here that I have made an endeavour to enlist the whaling captains of Dundee in our service, but have not yet learned whether it has been successful or not. I had copies of the British Association Abstract reprinted in a cheap form, and I sent a bundle to Dundee for distribution amongst the captains. Should Mr. Anderson yet give us any Mediterranean statistics, they can appear as an Appendix to our Report for 1882.
The lines of migration indicated in my Report of Scotland for 1879 and 1880, and conclusions drawn from statistics of these two years, appear to me to be borne out by those of 1881, as regards the semicircular form of the migration, an account of which I have already given in our last report (op. cit., pp. 18, 19).
The subject of heights of lanterns and their colours as attractions for birds has not developed as yet any fresh facts, but, with the conviction that they will yet do so, I still retain the table of heights given. Actual experiment, however, would very likely very soon set this part of the subject at rest (vide General Remarks, East Coast of Scotland Report, 1880, pp. 19, 20). A light-vessel or two placed in an equally favourable position with, let us say, the Isle of May or the Bell Rock on the east coast, or at some point north of Tweed, would, I believe, soon show us whether the preponderance of records south of the Tweed is entirely due to old-established lines of migration, or to the number of light-vessels on the English coast, or partly to both. It would, I think, assist in proving or disproving theories of land-communications which have been advanced and disputed by previous writers. At present we cannot positively state from our present data whether an actual or only an apparent preponderance of birds pass south of the Tweed in autumn. It appears a little curious to find, however, a highway of migration by the Pentland Firth so much further north than the stations mentioned. Writing from North Ronaldshay Mr. Tulloch remarks upon the usual scarcity of birds there, and says "they keep more direct for the mainland"; and he remarks also upon the abundance of birds seen in September and November at Pentland Skerries, where he was lighthouse-keeper for four years. He remarks on the abundance of Mountain Thrushes, Blackbirds, Owls, Woodcocks, Wrens, Robins, and Titmice which occur there when the wind is from the east, and from which station I have a large numerical return this year. This at first sight appears to be a contradiction of what I have said about the bulk of the birds passing south of Bell Rock, but, be it noted, the prevailing winds at Pentland Skerries from August 23rd to September 12th were from points between north and south by east, but never by west, and thereafter, between September 14th and October 10th, they were prevailing south to south-west, but never west or north-west. From October 14th they backed to north-east, and easterly winds again prevailed here on till late in November. The isolated position of the lights at Pentland Skerries, combined with the local prevalence of easterly winds, is perhaps sufficient to account for the large mass of the records. At all events I think the Pentland Skerries returns are deserving, both now and in future, of special attention and study, and I look upon it as a particularly interesting station.
Isle of May stands this year at the head of the list for numerical returns, I having received seven full schedules from Mr. Agnew, principally referring to autumn migration. Next comes Bell Rock, but two out of three schedules refer to spring migration, of which more anon. Then Sumburgh Head and Pentland Skerries, about equal, but the latter rather the larger, both returning three filled schedules, principally autumn migration.[8]
[8] Besides several more relating to 1882.
Regarding the spring migration, the Bell Rock and the Isle of May have hitherto held their place as yielding the largest returns, and very considerable numerical returns are given for 1881. Now, Sandwich Terns pass every spring up north along the coast of Forfarshire, but shoot off from the land again, and do not breed upon much of the suitable lands they pass over. An occasional pair of birds do remain and breed, as is shown by the nesting of this species on Inch Mickery, in the Firth of Forth, this past season, and on a previous occasion at the same place. In the same way we know that Grey Plover, Knot, and Bar-tailed Godwit shoot off the land at Spurn Point, as they are obtained there in full breeding dress, but nowhere to the north of it in breeding plumage, except in isolated cases. The routes of spring migrants, while they are usually more direct than those of autumn migrants, are perhaps more difficult to trace, and our statistics as yet are far from perfect. Since the above remarks were penned I have a well-filled schedule from Isle of May relating to the spring migration of 1882, which, however, will be included in our next Report.