« ПредишнаНапред »
it is a reasonable supposition that the instinct of orientation in woodcock causes all the birds to steer west or but a little south of west. Thus we should have birds which left the Norwegian coast landing in Scotland, others which started from Denmark striking our shore north of Lincolnshire, and those which left Germany and Holland making their appearance south of the Humber--all this roughly, and, to repeat, in normal weather. That birds starting from Norway not infrequently cut matters too fine in the direction of their flight, so that they thus miss the coast of Northern Scotland, and have to work back again when they discover from the undue length of their journey that they have overshot the mark—eventually if their strength holds out landing on the western coast of Scotland or Ireland and even the west coast of England -appears to point strongly to the assumption that the line they take by instinct is never very far south of west.
When, however, woodcock land on our western coast at the time of the prevalence of stormy weather, their doing so may more rightly be attributed to unfavourable winds having driven them out of their course than to their having willingly taken a line tending too much towards the north. That woodcock, like other birds, are frequently driven out of their course by gales which spring up after they have left their starting
point is certain; for their arrival, fleshless and starving, on the western seaboard is by no means infrequent, in fact occurs time after time under such circumstances. It has been put forward that on a dark night birds of such strong and swift flight as 'cock may well be supposed at times to pass right over our islands without knowing that dry land lies beneath them and find themselves at daybreak a long way to the west ; and that many of the birds that beat back over the Atlantic are birds which have passed over us in the darkness. This is possible, of course, but I do not think it likely.
One might say, speaking generally, that if there come a continuance of strong winds from the southeast round to the north-west during the few weeks woodcock are moving from their summer quarters, few birds will reach us and it will be a poor 'cock year : if the weather be still during that period it will be a moderate or fair year; while if the wind hold anywhere to the northward of these two points the year is likely to prove a good one. Suitable winds coming after the main body of 'cock have moved southwards will not repair the shortage; for the birds having once passed south and found themselves amid comfortable surroundings will remain there for the winter, or will work further south on the mainland if frost compels
them to move at all. Having once left to the north of them the point from which they would have started for the British Islands if they had not been deterred by adverse winds, they give up all thoughts of visiting us that season.
The woodcock, like all other birds, prefers a side wind for migration. Here again space does not allow one to indulge in full discussion of a particularly interesting matter. Briefly: a head wind is inimical to sustained flight unless it should be only a breeze, or but little more, and then it is of direct assistance ; and a stern wind is at all times inimical to sustained flight, for if merely a breeze it lessens the resisting power of the air, whilst if it amount to a strong current the resisting power is decreased in proportion.
Woodcock never reach us in daylight except when the weather has been unfavourable to their flight, and their journey has thus been delayed, or when, either through having taken too northerly a line or having been driven too far north by gales, they have missed our islands and found themselves compelled to retrace their wing-beats over the Atlantic.
| The migrating woodcock flies with greater swiftness than that of the current if flying with the wind, this being why the resisting power of the air is lessened. When a bird flies at a lower speed than the speed of the current, it receives assistance from the current, but not otherwise.
It is an open question whether woodcock collect together and start in falls at the time of the autumn migration, or whether each bird of a fall that reaches us acts on his own account, obeying a common instinctive impulse which prompts him to leave the northern shore at the same time that all his fellows leave it and to follow the same line that they follow. Judging by the habits of the bird while within our islands, I incline strongly to the belief that the latter is the case, that instinct impels him to make up his mind to start on the cross-sea journey at the same time that it impels other 'cock in the locality to do the same thing. When a dozen of these solitary birds occupy different nooks scattered about a hundred-acre wood, and all of them shift their quarters on the same night, it appears to me very much more likely that, obeying a common instinctive impulse, they act quite independently of one another than that they gather together first and then start together. In the same way I consider it very much more likely that at the time of the autumn migration the birds start independently than that they start in falls. They may, and no doubt often do, pick one another up at sea and end the journey in bunches. Bird instinct is much more potent and unerring than many people imagine. The instinct that prompts a hundred inde