ON THE MIGRATION OF BIRDS, 209 
permit me to cite, prove most undoubtedly that birds do return 
year by year to the same spot. 
On the east coast of Lincolnshire the arrivals of various species, 
during the autumn months of September and October, are so 
regular that they may be readily tabulated and predicted to a few 
days. The same phenomena may be observed, and with even 
greater certainty, at Heligoland during the periods of the vernal 
and autumnal migrations. No matter how the weather is at each 
particular periods of arrival, calm or strong, thick or clear, the birds 
come, and come, too, with marvellous regularity. They are scarce 
or plentiful as the case may be, for the abundance or scarcity of 
migrants at any special locality is due more or less to the state of 
the weather during the period of passage. The most favourable 
circumstances for birds passing the sea are calm still periods, or a 
light breeze, dead ahead, or a few paints free. A head wind that 
is not too strong is the very thing birds like best, but failing that, 
-a “beam wind,” to use a nautical expression, seems to be the best. 
A wind on their quarter, or one ‘aft—that is, having to fly before 
the wind, particularly if strong—is objectionable; it ruffles up 
their feathers and otherwise impedes their flight, soonest tiring 
them out. The consequences of unfavourable winds are that the 
birds alight on the first coast they reach for rest: under favourable 
circumstances they would have passed forward far overhead and 
unseen. Just as a man, fatigued by an arduous or difficult journey, 
pauses to rest on the way, so the birds alight for rest and quiet; 
within twenty-four hours, however, they are off again, each to its 
especial goal in forest, field, marsh, or sea-coast—a goal which it 
was their steady, predetermined, purpose to reach when they first 
took wing from the lone tundra, or ice-girdled shore, in the far- 
away north. ‘They trusted to no aérial currents to guide or drift 
them passively towards the sunny south, as seeds in the wash of 
the equatorial currents to the Hebridean shore, but to their own 
instinct and intelligence—an instinct which thus far has never 
failed. According, however, to Mr. Rowley, birds have neither 
impulse nor instinct: they are purposeless creatures with no will 
of their own, and the sport of every puff of wind. To carry out, 
then, this theory we must undoubtedly assign to the winds a 
far greater constancy than they are usually supposed to have, or 
than anemometers will justify us in supposing them to possess. 
The hypothesis is as wild as the wind itself, Nothing, indeed, is 
25 
