A STUDY OF THE FLIGHT OF SEA GULLS » 



By ROBEBT C. MlLLEB 



[With 4 plates] 



No one who has traveled on the ferries which ply across San 

 Francisco Bay can have failed to note the sea gulls which follow 

 constantly in their wake. Hour after hour, day by day, sometimes 

 at night even, they may be seen winging tirelessly after the cumbrous 

 boats, sailing high like paper kites, or sporting in the currents of 

 air about the stern, or scuffling noisily for bits of food thrown over- 

 board by the passengers. In the earliest dawn they are on duty, 

 looking like gray specters in the morning mists, and on moonlit 

 nights they are abroad at least until midnight, flapping along like 

 giant bats in the semidarkness. 



Of the many thousands of people who have watched the gulls on 

 the bay and admired their beauty, probably most have thought of 

 their graceful evolutions only as a part of nature's artistry. But 

 for the ornithologist, the aesthetic is not the sole nor even the prin- 

 cipal interest which attaches to them. Rather does he remark the 

 marvelous powers of flight which enable so large a bird to keep 

 aloft for long periods of time without fatigue, and the rapid coor- 

 dination which permits it to take advantage of every current of the 

 shifting air, and to maintain its equilibrium under the most adverse 

 circumstances of wind and weather. 



On account of their large size, easy flight, and relatively slow wing 

 movements the gulls have long been looked upon as peculiarly favor- 

 able subjects for studies of avian aeronautics. However, although 

 our knowledge of their flight is rather extensive, as yet it is far from 

 complete. The data assembled by different observers are frequently 

 not in agreement, and, as Hankin (1913, p. 253) has pointed out, 

 two authorities as competent as Maxim and Headley have published 

 statements diametrically opposed. Such contradictory ideas must, 

 in most cases, indicate not that the observations on which they rest 

 are incorrect but only that they are inadequate; a type of behavior 

 which is observed on one or two occasions may be entirely lacking 



1 Reprinted by permission from the Condor, Vol. XXV, January. 1923. The writer of 

 this essay was awarded the Cooper prize in ornithology offered at the University of Cali- 

 fornia in 1921-22 for the best study of any subject concerned with birds. 



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