356 THE STRUCTURE AND LIFE OF BIRDS CHAP. 
spot. Gilbert White wondered at the annual return 
of the same number of Swifts each year (exactly 
eight pairs) to Selborne. And now it has been put 
beyond a doubt that many migrants return to their 
old nesting-place. When a Nightingale in Abyssinia 
is seized with the migratory impulse, his heart is filled, 
not with a vague yearning for the north, but with a 
yearning for one familiar spot. 
The Time Occupied in Migration. 
The flight in spring is generally,as I have said, 
more rapid than in autumn. In spring the birds have 
a definite purpose before them. They wish to set 
about their nest building, and they grudge every hour 
of delay. In autumn they pause and loiter in Central 
and even in Northern Germany. It is difficult to 
estimate the exact time occupied by the spring flight, 
but some evidence is obtainable. That particular 
form of Bluethroat that has a red spot in the centre 
of the blue, winters in Egypt, often in the regions of 
the Upper Nile. It occurs frequently in Heligoland, 
whereas in Germany only the form that has a white 
spot is found. Since, then, according to the evidence, 
Heligoland is the first place at which it stops as it 
travels to its breeding stations in Northern Scandi- 
navia and. Russia, it would seem that it covers the 
whole distance from Egypt to Heligoland—over 1,500 
miles—in a single flight. This is very difficult to 
believe, and to follow Herr Gatke when he maintains 
that the flight is accomplished in a single night is still 
more difficult. As evidence, he mentions the interesting 
