132 THE FLIGHT OF BIRDS 
glide he generally hits off the up-current, but not in- 
frequently he fails and@fias to put in a few strokes. 
Small pieces of paper thrown over the stern show that 
the up-current is not always at the same distance 
behind the ship. Hence this method of advance, 
though a very gay and lively one, has, whenever I 
have observed it, been lacking in precision. How- 
ever, when the conditions are not perfect, the Gull 
may be trusted to make the best of a bad job. I 
have just been watching some Gulls that were 
following a small steamer. The wind was blowing 
nearly at a right angle to the vessel’s course. There 
was an up-current available, but apparently an 
unsatisfactory one, for there was never an advance, 
except for a few moments, without very distinct 
wing-beats. The Gulls faced the wind and, while 
almost uninterruptedly beating with their wings, 
advanced nearly sideways, right wing leading. Had 
there been no up-current, such a style of flight would, 
I believe, have been impossible. They must have 
been inclining their bodies slightly downwards, from 
the left side to the right, so as to induce movement 
in the direction desired. I am quite aware that 
birds, when they wish to advance at right angles 
to an ordinary horizontal wind, make a half-turn 
towards it, so as not to be swept out of their course. 
But here was an instance of a much more complete 
turn and an advance almost sideways. 
Clever as the Gull is at such methods of advance, 
the Shearwater, to my mind, is a yet more perfect 
master of the art. He does not require any steamer 
to help him. If only there are waves and a wind, 
he has all the conditions that he wants. He keeps 
