234 Townsend, Use of Wings and Feet by Diving Birds, [j^y 



THE USE OF THE WINGS AND FEET BY DIVING BIRDS. 1 



BY CHARLES W. TOWNSEND, M. D. 



Birds that dive and swim under water may be divided into two 

 main classes, — those that habitually use the wings alone for sub- 

 aqueous propulsion, and those that use the feet alone. The 

 following paper includes my own observations which have been 

 made only on wild birds and have been recorded at the time, and 

 of records given me by other observers, as well as of those collected 

 from literature. These two last named include observations on 

 captive birds in tanks, which I believe are of value, for, as we shall 

 see, the birds that habitually use their wings alone under water 

 when in the wild state, and those that habitually use the feet alone, 

 follow this rule even when confined. 



In watching wild birds diving I have concluded that those that 

 spread their wings just as they enter the water, use them under 

 water, while those that keep the wings tightly pressed to the sides, 

 and often execute graceful curves in diving, sometimes leaping 

 clear of the water, depend on the feet alone. The truth of this 

 conclusion I have confirmed in some instances by observing the bird 

 under water; in other instances the conclusion has been borne out 

 by the observation of others, so that the rule is, I think, a good one. 

 Since formulating this rule I have found that Edmund Selous (15) 

 expresses this same idea when he says: "This opening of the wings 

 in the moment of diving is, I believe, a sure sign that they are used 

 as fins or flippers under water." And again (16): "On the other 

 hand cormorants, shags, and mergansers, birds which do not use 

 their wings in this way, dive in a quite different manner. Instead 

 of the sudden, little, splashy duck, as described, they make a 

 smooth gliding leap forwards and upwards, rising a little from the 

 water, with the neck stretched out, and wings pressed close to the 

 sides to enter it again back foremost, like a curved arrow, thus 

 describing the segment of a circle." 



In the Loons and Grebes, the wings are small, but the legs are 

 large and powerful. The femur is short and stout, thoroughly 



1 Read before the Nuttall Ornithological Club, February 15, 1909. 



