birds pass over the field of his telescope at a height of from 
1500 to 15,000 feet ; and the most remarkable thing of all 
was the fact that the lowest birds were flying upwards, as 
if they had risen from the immediate neighbourhood and 
were seeking the proper elevation to continue their flight. 
As has already been remarked, when nearing their destina- 
tion migrating birds descend, though still many miles from 
land. Should a gale be raging they fly so low that they 
barely top the waves. And this, apparently, to escape, 
so far as is possible, the force of the wind. Larks, starlings, 
thrushes, and other small birds, can sometimes be seen 
during daylight crossing the North Sea in their thousands. 
At such times many will often afford themselves a brief 
rest in the rigging of ships, homeward bound, but the main 
host hurry on. The beautiful golden-crested wren, our 
smallest British migrant, is one of these. A glance at our 
charming coloured Plate will show at once that the wing is 
not that of a bird of strong flight. There is no more inter- 
esting experience to the bird-lover than that of watching the 
tired travellers drop earthwards, as they leave the dreadful 
sea behind them. 
With all birds yet retaining the power of flight there is 
always a liberal ‘“‘ margin of safety’ in regard to the wing 
area. That is to say, this is always in excess of the minimum 
area necessary to make flight possible. This much, indeed, is 
N 181 
