116 THE FLIGHT OF BIRDS 
than most migrants, may sometimes get into the 
higher current? If oc®asionally they make very 
good times, apparently against the wind, may not 
the explanation be that they have got into a stratum 
of air that was moving in another direction? Mr. 
Glaisher, as I have pointed out, found that the 
direction of the wind sometimes changed at a height 
of no more than 500 feet. A Homing Pigeon, when 
he is starting, circles upward and takes his bearings, 
looking out for landmarks in the direction of the cot 
for which he is yearning, and it is possible that as 
he rises he may sometimes find a favourable breeze 
though the lower one is adverse. I suggest this, 
since a high authority on Homing Pigeons maintains 
that anticyclonic weather is the important thing, 
not the direction of the wind. Looking through 
the best records, however, I find that the low-level 
wind has been such as to propel the birds and add 
to their velocity. If they find themselves in a 
uniform horizontal current travelling in the direction 
in which they are travelling, there is no reason why 
they should be conscious of the movement of the air, 
unless, indeed, they mark the rapidity with which 
they pass their landmarks on the earth’s surface 
and draw the inference that there is a tail-wind 
adding its velocity to theirs! They must, of course, 
fly faster than the wind, or the air will give them no 
support. Now, supposing their own efforts give them 
a velocity of 35 miles an hour and the wind has a 
velocity of 25, the two together make up the splendid 
total of 60. At present I say nothing about the 
question whether birds are able to fly with the wind 
when it is blowing a gale. Somehow the belief has 
