164 MY NATURE NOTEBOOK. 



south-west The birds do not travel until they feel the 

 chill of coming winter in the cold breath of winds that 

 have blown over fields of spreading ice, nor do they 

 risk a sea-passage until they must So they almost 

 always " take off," for their leap across the sea, from 

 some cape or promontory jutting out to the south or 

 south-west, and arrive on coasts which bulge out, so 

 to speak, to meet them. From the height at which 

 they fly detected only, as a rule, by the telescopes 

 of astronomers they can see land at an immense 

 distance, and the momentum which they gain by a 

 long, gliding descent enables them to make the land 

 at marvellous speed, even across the wind. Thus, 

 although birds always depart with the wind, they do 

 not always appear to arrive with it. 



MIGRATION TURNED BACK. 



Last week persistent east winds brought over to 

 England many hosts of birds from Norway, some, 

 like the redwing-thrushes and bramblings, coming to 

 spend the winter with us, and others, like the belated 

 black-caps and the swallows, only passing on their 

 way to Southern Europe and Africa. During this 

 week, however, days of continuous south-westerly 

 winds have checked migration altogether, and even 

 to some extent turned it back. The willow-wren 

 and the house-martin, for instance, came back to the 

 east coast, and, in the case of the latter bird, one pair 

 which returned to a particular spot seemed to be the 

 very same pair, which had been the last to leave. 

 Unlike travelling martins, which, when halting in a 

 strange place, fly up to one after another of the 



