"p.p'i:; Pobbbs, Concerning tin- Flight of Gull .'J./.i 



CONCERNING THE FLIGHT OF GULLS. 



BY ALEXANDER FORBES. 



Mk. William Brewster has recently published in this journal l 

 a most interesting and important account of the soaring of gulls to 

 windward. His account is especially valuable since his observa- 

 tions were made with such care and accuracy that no room is left 

 for doubt that, the birds soared for long distances horizontally 

 again I a itrong wind in the neighborhood of a steamer, without 

 the aid of wing heats. The phenomenon is of such interest from 

 the standpoint of physics that it seems to me to warrant further 

 discussion. 



The essential features of his observations are briefly as follows: — 

 The steamship on which Mr. Brewster travelled was steaming at a 

 rati' of about fifteen knots an hour, witli a wind at first blowing 

 al a late of about twenty mile-, an hour from about two points off 

 the port bow, ami later freshening to a gale of about thirty-five 

 miles an hour and shifting somewhat more nearly dead ahead. 

 Under these conditions a large number of gulls accompanying the 

 ship glided the greater part of the lime on set wings; at first flapping 

 their wings at fairly frequent intervals, but, as the wind freshened, 

 li and less frequently until at the height of the gale most of the 

 birds could be seen to glide "over distances certainly exceeding a 

 mile, w it bout a single wing beat." He says of them when gliding: 

 " t heir respective positions in relation to each other and to the ship 

 were so accurately and systematically maintained that whenever 

 I got our of t hem in line with any fixed object on the deck I could 

 often hold it there, without myself moving again, for several suc- 

 < < ive minutes." Thus it is clear that their motion was horizontal 

 not downward, and that its continuance with unabated speed elimi- 

 nates tin possibility of explaining it as the result of momentum ac- 

 quired in a previous downward swoop, or from previous wing beats. 



Tlie distribution of birds in relation to the ship was as follows: — 

 "A few followed the creamy wake of the ship or poised directly 

 over h'-r jut to the rear of her smoke-stack but the majority kept 



» ' The Auk,' .Jan., 1012, p. 85. 



