78 



Snipe * drumming ' 



the sole cause, that analogous noises would not be uncommon 

 throughout the class. The poise of a hovering Kestrel, for example, 

 motionless with rapidly vibrating wings, is unattended by any sound 

 whatever that is audible to our ears. 



As regards the primary quills themselves, I am not aware that 

 any one, so far, by any experimental process has extracted the 

 drumming noise from them, as has been done with the outside 

 feathers of the Snipe's tail. That the isolated outside feathers can 

 be caused to make the drumming noise has already been mentioned ; 

 and I should have added that these particular feathers are peculiarly- 

 constructed — the shaft stiff and sabre-shaped, the rays of the web 



Fig. 7 



long and strongly bound together. No other bird (outside this 

 family) appears to possess tail feathers of the same shape and 

 structure. 



The characteristic out -spreading of the tail in the drumming 

 Snipe suggests most strongly that the tail has some relation to the 

 sound, and is not merely expanded for the purpose of guiding the 

 flight (Fig. 7). 



4. Wing and Tail. — Everything I have said so far points, I 

 think, to the sound being caused by the combined effect of wings 

 and tail.* The rapidly beating wings, whether they themselves 

 hum or not, throw a strong current of air onto the outermost 

 feathers of the tail, and set them in vibration. 



The position of the wings in relation to the tail is of importance ; 

 the wings are half closed, and the tail fully expanded, and this is 



* H. Gadhumer (" Xaumannia," 1853, p. 411) urged that both wings and tail are factors 

 in the sound production. Colonel I^egge (" Birds of Ceylon," iSSo, p. 1,219) considered that the 

 sound is primarilv caused bj' the rapid wing-beats, assisted by the downward rush, but that the 

 wind driven by the wings across the tail-feathers (which are spread fan-wise, with the outer rectrices 

 standing out at right angles to the central feather) produces a secondary sound. A. Thorburn, 

 " British Birds," 1Q18, iv., p. 28) says that the sound is apparently caused by the vibration of 

 the outer tail-feathers, though the wings may ahso be concerned. He gives a beautiful illustration 

 of a" drumming " Snipe (pi. 65), which nearly resembles Bahr's figure. Another similar figure 

 occurs in " The Home-life of some Marsh-birds," by E. L. Turner and P. H. Bahr, Igoy. p. 23 — 

 Editor. 



