33 



first fathom, and ten for every fathom thereafter. 1 If I under- 

 stand this rule correctly it would require about three minutes 

 for a bird to descend 100 feet and return to the surface, and 

 over five minutes might be required for 200 feet. A Mer- 

 ganser, held under water, was drowned in five minutes, and I 

 do not recall any authentic instance where birds diving natur- 

 ally in water a few fathoms in depth, and coming up undis- 

 turbed, have remained beneath the surface more than three 

 minutes, although periods of four and five minutes have been 

 reported. Therefore it is probable that birds by use of wings 

 and feet are able to make faster time in descending to the 

 depths than they ordinarily make in diving in shallow water. 

 Otherwise they would have little or no time to feed on the 

 bottom. 



In reviewing the evidence that we have regarding the use of 

 wings under water, I find no comparisons that assure us that 

 birds move faster below the surface by the use of wings alone 

 than by use of the feet only. But assuming for the sake of 

 argument (1) that the wing-surface used under water is at least 

 three times as large as that of the feet, (2) that the pectoral 

 muscles which assist in propelling the wings downward and 

 backward are perhaps three times as large as those which move 

 the legs, and (3) that the wing-beats are as rapid as the foot 

 strokes (and allowing that the propulsive force of the wing can 

 be fully applied), we might well believe that birds move faster 

 under water with wing propulsion than with foot propulsion. 

 However that may be, we have seen that in the case of loons 

 and grebes the birds apparently move faster when both wings 

 and feet are employed than when the feet only are used. 

 Some say faster, others much faster, and others very much 

 faster. 



In this preliminary report nothing more need be said con- 

 cerning the behavior of the families under consideration. Con- 

 siderable evidence has been collected in respect to the under- 

 water_ behavior of several families of diving birds. This must 

 await another opportunity for publication. 



i Dewar, J. H.: British Birds, Vol. XIII, No. 12, May 1, 1920, p. 315. 





