90 Brewster, Notes on the Flight of Gulls. [^^^^ 



conclusions.^ I cannot accept all of these, however, and I am 

 especially unwilling to endorse his belief that birds gliding to 

 windward depend for means of propulsion largely if not wholly 

 on uplift afforded by powerful ascending currents of air such 

 as must always rise above a vessel when heavy wind is striking 

 against and deflected from, her sides. The possibility of this 

 was thought of and at first more or less favorably considered by 

 Dr. Allen and me as we watched the Gulls from the deck of the 

 * Arabic,' a month or more before Mr. Tydeman's article came 

 to our notice. But I dismissed it altogether from my mind after 

 repeatedly seeing birds hundreds of yards behind the steamer, or 

 fifty or more yards to one side (alwaj's the windward one) of her, 

 or even well in advance of her, gliding on set wings in precisely 

 the same manner and quite as ceaselessly as those which hung 

 about her flanks. It seems inconceivable that her presence or 

 movement could have caused vertically rising currents of air to be 

 regularly maintained at such distances from her as those just 

 mentioned, or that they could have been thus constantly and 

 generally maintained by other influences when the ocean all about 

 her was swept by a wind blowing over thirty miles an hour. I 

 even doubt if they extended much above her upper deck for there 

 I was lashed incessantly in the face by what seemed to be hori- 

 zontally-racing wind, while several of the Gulls were often sailing 

 fifteen or twenty feet higher still, perhaps directly over me. On 

 the other hand it must be admitted that I have never known any 

 of these birds to glide far to windward except when accompanying 

 a steamship, a fact which apparently lends some support to Mr. 

 Tydeman's contention, although not necessarily having such sig- 

 nificance since it may reasonably be interpreted in other ways. 



Conducted of necessity through opposing and invisible air 

 currents constantly varying in force and also somewhat in direction 

 the gliding flight of the Gulls seems very wonderful, however it be 

 explained. It would be impossible of execution were not the birds 

 endowed with some intuitive sense which enables them to instantlv 



1 So many of these are in close accord with mine that it may be well for me to 

 state that the present article is based almost wholly on observations and impres- 

 sions recorded in my journal or other notebooks before I knew anything about 

 Mr. Tydeman. It is true that some of my views have been modified since his 

 article was brought to my notice but this has been due not so much to its influence 

 as to helpful criticisms and suggestions contributed by ornithological friends. 



