1907.] "bleating" op the snipe. 19 



In order to ensure the success of the experiment it is necessary 

 (1) that the feathers be placed so that the narrow edge, the outer 

 web, shall encounter the resistance of the air ; (2) that the feather 

 be firmly bound to the pin, so that it cannot turn on its support ; 

 (3) that the string be tied to one end of the stick, so that the 

 long axis of the stick makes an angle with the direction of the 

 string, if I may so put it, so that a vibratory motion is imparted 

 to the stick as a whole, thus simulating the tremulous motion 

 of the Snipe's wings during the descent ; (4) lastly, that the 

 apparatus be moved at a uniform rate and not too fast. 



It is then found that after a period of silence the feathers begin 

 to vibrate : first, the long-drawn-out note, which I may represent 

 as " whii wh a u u," becomes gradually audible, it is then succeeded 

 by a series of high and low notes " bah-bah-ah-a,h," resembling 

 the bleat of a young goat, lasting 3-5 sees., followed by a pause 

 of equal length. This is repeated as long as the appai-atus is 

 revolving at a uniform rate. It is found that the individual tail- 

 feathers, of which I collected a good number during the winter, 

 vary consideiably both in size, breadth, and markings, and, as 

 might be expected, the note produced varies according to their 

 physical characteristics. Thus a long narrow feather produces a 

 sound of far higher pitch than a broader one of the same length 

 (vide text-fig. 4). This fact I have noted when comparing the 

 sound made by several birds when performing the nuptial evo- 

 lutions over their breeding-grounds. To ascertain which part of 

 the feather is essential in the production of the sound, I have cut 

 ofi' the narrow outer web, without altering the bleat in any way ; 

 but if the barbs of the inner web be so disarranged that there is 

 a break in their continuity, the web ceases to vibrate, and no 

 sound is produced. That the vibration of the inner web is the 

 active causative agent may be seen by the following simple 

 experiments : — The feathers are attached to a cork, with the outer 

 web held away from the observer, so that tlie narrow outer web 

 shall cleave the resistance of the aii-. Thus affixed they are held 

 out of the window of a train, or while riding a bicycle. As the 

 resistance of the air is encountered the inner web begins to 

 vibrate, slowly at first, bvit as the train gains speed, so rapidly 

 that its outline is entirely lost, and it becomes a blurr ; a low 

 humming sound is at first heard, which soon reaches the typical 

 pitch of the bleat. When the train has reached the speed of 

 some 20 miles an hour, the whole feather will vibrate on the pin. 

 If the feathers are at all loose on their pins it is curious to observe 

 how they will always turn round so that the narrow outer edge 

 encounters the resistance of the air. Furthermore,, if the feathers 

 be damped, they appear to act better, thus explaining, perhaps, 

 why Snipe are found to be liable to bleat in damp weather. I 

 think this simple experiment readily explains away the " adverse 

 cases " of Prof, Altum (' Ornithologisches Centralblatt,' Oct. 1880) 

 already mentioned. 



That the bens bleat as well as the cocks is now, I suppose, a 

 well-known fact {cf. von Preen, ' ISTaumannia,' 1856, pp. 426,427, 



9* 



