AVES PROCELLARIID^E. 127 



ming the surface in searching for its food. This movement is usually 

 seen most clearly when the sea presents a slightly undulating surface ; 

 and when the bird strikes the water in performing a slight curve in its 

 flight, one can see that it is invariably the outer leg that is used. The 

 object of this manoeuvre seems to be to give the body sufficient upward 

 impulse to prevent the wings from becoming wetted in rising from near 

 the surface. I have often observed the Atlantic storm petrels steady 

 themselves on the water with both legs together, but have never seen 

 them perform this one-legged 'kick/ like their congeners of the Pacific. 

 There are contradictory statements in natural history works as to whether 

 petrels do or do not follow ships during the night time. Those who 

 adopt the negative view of the question maintain that the birds rest on 

 the waves during the night and pick up the ship next morning by follow- 

 ing her wake. For a long time I was in doubt as to which was the cor- 

 rect view to take, although I had often on dark nights, when sitting on 

 the taffrail of the ship, fancied I had heard the chirp of the small petrels. 

 At length I became provoked that after having spent so many years at 

 sea I should still be in doubt about such a matter as this, so I began to 

 make systematic observations, in which I was assisted by the officers of 

 watches and quartermasters, who were also interested in the matter. 

 The result is that I am now quite certain that the storm petrel and Cape 

 pigeon do follow the ship by night as well as by day, and that, moreover, 

 the night is the best time for catching them. Every night, for a time, I 

 used to tow a long light thread from the stern of the ship ; it was about 

 sixty yards long, and fitted at the end with an anchor-shaped piece of 

 bottle wire, which just skimmed along the surface of the water and yet 

 allowed the thread to float freely in the air. I found this device a great 

 improvement on the old-fashioned method of using several unarmed 

 threads, and in this way I caught at night-time, and even on the darkest 

 nights, both storm petrels and Cape pigeons ; the latter, however, usually 

 breaking my thread and escaping. If I sat down quietly and held the 

 line lightly between my finger and thumb, I would feel every now and 

 then a vibration as a bird collided with it. On moonlight nights, more- 

 over, one could always, by watching carefully, see the big Cape pigeons 

 flitting about the stern of the ship." (Copp., Cruise "Alert," pp. 87-88.) 



