[CHAPTER VIII]
THE PERILS OF MIGRATION
The dangers to which migratory birds are subjected during their journeys are but little less than those which would befall them if they remained in unsuitable zones. During long oversea passages fatigue and hunger weed out the weaklings, sudden storms and adverse winds strike them where no land is near, and they are carried often far from the goal they aimed at. Predatory birds accompany them, taking toll en route, and predatory man waits for the tired wanderers with gun and net. Shore birds may rest upon the waves; sandpipers have been seen feeding as they walked upon the drifting weed of the Sargasso Sea, and steamers and other vessels frequently provide a rest for weary birds; but what happens to the many which find no haven? "Woe to the luckless warbler whose feathers once become water-soaked!—a grave in the ocean or a burial in the sand of the beach is the inevitable result," says Mr Cooke. A storm on Lake Michigan during spring migration piled many birds along the shore, and in the wider Gulf of Mexico many hundreds of passage birds were seen to fall into the water when caught, but 30 miles from land, by a violent "norther." Other similar sudden disasters have been recorded off our British coasts, even so far back as 1786, when, as quoted by Southwell, a Newcastle collier passed through water off the Suffolk shores black with vast numbers of drowned woodcocks.
During normal migration birds may be brought to a lower elevation by strong contrary winds, or they may be bewildered by fogs and cloud and dropped nearer the surface; it is then that the travellers meet with disaster at our coastwise lights.
Mr Tomison records some of his experiences of migration at Skerryvore [(52)]. He never saw a bird at the windows when the moon was shining, and on clear nights the passing crowds go on without a pause. But on hazy nights, with an easterly wind and drizzle, or during fogs, if large numbers of migrants are passing, hundreds may be seen flying in all directions, "all seemingly of the opinion that the only way of escape out of the confusion—is through the windows of the lantern." On one September night, when he was standing on the balcony, he likens the appearance of the birds to a heavy fall of snow. "Thousands were flitting about; hundreds were striking against the dome and windows; hundreds were sitting dazed and stupid on the trimming paths; and scores falling to the rocks below, some instantaneously killed, others seriously injured, falling helplessly into the sea." On the following night when many fieldfares, redwings, thrushes and other birds were passing, he says—"Sometimes we use the terms hundreds and thousands without thinking what these figures mean but on this occasion when I say thousands were killed I do not exaggerate in the slightest."
Mr W. Brewster's account of his experiences at the Point Lepreaux lighthouse [(8)], shows that similar disasters occur in Canada and the States, as indeed they do wherever there are passages of birds. On a foggy evening in September 1885 "as soon as the sky became overcast small birds began to come about the light—with the advent of the fog they multiplied tenfold in the course of a few minutes" and many struck. "About the top of the tower, a belt of light projected some thirty yards into the mist by the powerful reflectors; and in this belt swarms of birds, circling, floating, soaring, now advancing, next retreating, but never quite able, as it seemed, to throw off the spell of the fatal lantern.... Dozens were continually leaving the throng" of birds which had flown to leeward, "and skimming towards the lantern. As they approached they usually soared upward, and those which started on a level with the platform usually passed above the roof.... Often for a minute or more not a bird would strike. Then, as if seized by a panic, they would come against the glass so rapidly ... that the sound of the blows resembled the pattering of hail." During his stay no birds came to the light except during dense cloud or fog, and they came in greatest numbers when an hour or two before the fog the sky was clear.
The experiences of Eagle Clarke, Seebohm and others who have spent migration seasons at lighthouses might be quoted, but these two give a vivid description of what regularly takes place when weather conditions are unfavourable. Steady white lights are the most fatal to migrants, revolving lights, if white, are struck by some birds, but red lights seldom attract the passers. Mr Eagle Clarke thinks that birds are actually decoyed from their path and arrested in their course by the action of the lights; he says that a change from white to red lights at the Galloper Lightship stopped bird attraction.
On the mainland a new high building or tower, new telegraph wires or other erections, until their presence is familiar, take toll of passage birds.