On September 22nd, he says--"The favourable meteorological conditions of yesterday--fine weather and moderate south-east breezes,--has had a marked effect, for to-day goldcrests are swarming everywhere." But what does he mean? Favourable to him as an observer or to the goldcrests? Surely the birds did not aim for Fair Island; were not these weak-winged birds probably making for the south, when the south-east wind caught them and drifted them to the west? Fair Island was a refuge, but hardly the objective of their flight (17).
Compare this with Cordeaux's notes of another goldcrest immigration, this time to the Lincolnshire coast (23). On October 13th the wind was north to north-east in the afternoon, light but increasing in force, the weather clear and bright--a few birds arrived. They had started under favourable circumstances. Shortly after midnight on the morning of the 14th, the wind got full east, with quite half a gale and heavy beating rain, continuous to the morning of the 16th; the nights were very dark. "During this time the immigration was immense," and most of the birds were goldcrests. Cordeaux's idea that these were not normal immigrants but birds which were passing probably from north-east to south-west, when the easterly gale caught them, is probably correct.
I have referred to birds starting at a high elevation. Service says that in normal departure from the Solway, most birds mount to a high altitude, but "a strong beam wind will bring the birds--even those of strongest power--down to 200 to 500 feet of the surface, and it is interesting to see whole flocks with heads turned almost completely to wind, and yet travelling along at nearly their normal speed, at right angles to their position" (46). Mr Tomison mentions rooks, daws and hooded crows driven to Sule Skerry by south-east winds in March, leaving two days later in a westerly gale. They, at any rate, did not object to a strong wind which was in the right direction.
I have mentioned Mr F. J. Stubbs' paper on the "Use of Wind" (50), and I believe that there is much more in it than is actually proved by low-level observations. I doubt if birds always intentionally make use of strong winds, currents which would carry them for great distances at a considerable speed, but the preliminary ascent may be to search for these currents. Cyclonic and anticyclonic winds, even when at an altitude of some thousands of feet, would carry them easily, and probably it is the wind-borne individuals, parties, or even hosts, which drop for a refuge to the first island they see when carried far from their migratory path. They are carried rather than drifted from their pathway, borne in the moving current whether they wish it or not. Provided that the cyclonic winds are fairly steady in direction and force, sweeping round and inwards towards their centre, we may in imagination trace the pathway of our so-called lost wanderers to far distant islands; without many more upper-air observation stations, we cannot actually prove the route.