THE PROBLEM OF WHISKERS 251 



formed by Ducks in the water, has no doubt for 

 its primary object the loosening of the bottom to 

 stir up lurking prey. 



The cere, or soft skin at the base of the beak in 

 Parrots, birds of prey, and Pigeons, may have some 

 tactile value, preventing these birds from plunging 

 the beak over the nostrils in the soft food, flesh 

 or fruit, on which so many of these birds subsist ; 

 at any rate, the only other groups in which the 

 beak has a soft covering are the Ducks and Flamin- 

 goes, in .which only the end and edges, as has been 

 said, are horny, and these are habitually mud- 

 feeders, and seek food by feeling. The soft flanges 

 or lips, at the base of the bill in the nestlings of 

 Passerines, Hoopoes, and Woodpeckers, are also 

 sensitive to touch, and no doubt aid the young 

 "yellow-beak" to perceive the food the parents 

 offer it ; but they are not found in other young 

 birds even of the helpless kinds, and never in active 

 chicks. 



Whiskers like those of many mammals are found 

 round the face and base of the biU in the Apteryx 

 or Kiwi, so beast-like in its behaviour, and pre- 

 sumably they may serve as feeling-organs in the 

 same way ; but it is less easy to divine the use of 

 the bristles found at the sides of the beak, and 

 often where it joins the forehead, in many birds 

 which feed on flying insects, and specially conspicu- 

 ous in the Nightjars and Flycatchers. They may act 

 as guides for the snap of the beak, but they are 

 absent in many birds of somewhat similar habits 



