46 THE ORNITHOLOGIST. 



touching the nesting habits of the Sparrow-hawk, will lead 

 future historians to cull their so-called facts more from nature 

 herself than from the publications, excellent though they be, 

 which may chance to lie on their book-shelves. 



EFFECT OF WINDS ON THE FLIGHT OF BIRDS. 

 By F. B. Whitlock. 



I am interested in the paper on the above subject by Mr. 

 J. H. Gurney, which is reprinted from the " Ibis " in the current 

 number of the Ornithologist. I do not, however, quite follow 

 him when he writes — " The action of the wings is greatly 

 regulated by the direction and velocity of the wind, though, 

 joined to this, the actual motive power is gravitation to the 

 earth's surface." The first part of this quotation is no doubt 

 true enough, but I fail to see how the actual motive power 

 of flight can be gravitation to the earth's surface. 



It seems to me that if this were the case, birds would have 

 great difficulty in rising from the ground, unless the direction 

 of their flight during the first few strokes of their wings were 

 always directed towards the point from which the wind 

 happened to be blowing at the time. We know that this is 

 by no means a necessity, though ducks usually, in rising 

 from the water, adopt this course. With the latter species, 

 however, flight is commenced by a sort of upward spring 

 rather than by power of wing. 



To me the motive power of a bird's flight always seems to 

 be attained in a similar manner to that used in propelling a 

 rowing boat. To illustrate this we have only to substitute 

 wings in the place of oars, and the air for the water. There is 

 one important distinction, however, the air being so much 

 less buoyant than the water, a downward as well as forward 

 stroke of the wings is also necessary to prevent the bird from 

 sinking to the earth ; but at the same time the wings act in 

 a similar manner to the oars of the boat and propel the bird 



