T. A. Coward

“ I have seen ducks in a blizzard rise head to wind and fly rapidly, making no progress but maintaining their position over the water, to which they dropped again when the storm passed. Some black-headed gulls on the same water did not attempt this manoeuvre, and in a few seconds had vanished down wind. The swimmer, in a swiftly-flowing river, may hold himself in position so long as he can swim at the same rate as the stream ho is contending with, but he cannot make headway if the speed of the water exceeds his. ”

“ Many birds, especially day-migrating swallows, hooded crows and other birds, frequently travel at slight elevations; it is not unusual to see birds at sea flying a few feet only above the waves Mr W. Eagle Clarke, whose systematic observations demand the profoundest respect, again and again urges that the direction of the wind has little effect upon migration, but that the force of the wind may make migration impossible. ”

“ Birds are warmer-blooded than ourselves or other mammalia, and are capable of sustaining life in rarified atmospheres where these could not. By a simple mechanical ascent, they can reach, within a league or two, regions and conditions quite beyond human knowledge: where, selecting favouring air-strata, they may be able to rest without exertion; or find meteorological or atmospheric forces that mitigate or abolish the labours of ordinary flight, or possibly assist their progress. ”

“ He points out that Gätke and others imagine that a bird flying with the wind would suffer inconvenience through the wind ruffling up its feathers. It is surely evident that a bird supported in a moving medium could not progress at any slower rate than that medium; the bird is not flying on one stratum of air with another moving with a different speed immediately above it ”

“ A warbler flying leisurely, say at 10 miles per hour, in a current of air which was travelling at 20 or more miles an hour, could accomplish the journey across the North Sea—say 300 miles, in ten hours. Allowing much higher rates of speed for strong-winged species, and greater force of wind, some of the marvellous distances covered by migrating birds cease to be mysterious Prof. ”

“ They arrive often one by one and "seem to drop literally from the clouds," but when they actually departed it was easy to see their method. They "fly upwards and onwards, then they hesitate, fly sideways once or twice, again attempt an upward and onward flight, hesitate again, and down they come once more to earth." ”

“ THE HEIGHT AND SPEED OF MIGRATION FLIGHT
In the last chapter reference was made no the great height at which birds may fly on migration. Certain species, even comparatively weak-winged ones, appear normally to fly high, Whilst others, Often birds with pointed Wings and great aerial powers, usually proceed at low elevations ”

“ He adds an important note: "A number of birds were seen flying upwards, crossing the moon, therefore, diagonally, these evidently being birds which had arisen in our immediate neighbourhood, and were seeking the proper elevation at which to continue their flight," but the direction of flight of most of the birds which were observed was parallel to the earth's surface and southerly. ”

“ Allowing this, and also taking into consideration the undoubted fact that birds are frequently held up by strong winds on the shore before starting oversea journeys, is there any proof that they do not actually avail themselves of fairly steady strong winds when they reach the upper air? ”

“ Gätke frequently mentions birds raining down from the sky, appearing first as mere specks, and dropping vertically to the island, and others when departing "with breasts directed upwards and rapid powerful strokes of the wings; fly almost perpendicularly upwards." ”