BIRDS AT THEIR BEST 29 



has been lost or has become more or less indistinct. 

 In some cases it is because there was nothing dis- 

 tinctive or in any way attractive in the notes ; in 

 other cases because the images have been covered 

 and obliterated by others the stronger images of 

 closely-allied species. In the two American families 

 of tyrant-birds and woodhewers, neither of which 

 are songsters, there is in some of the closely-related 

 species a remarkable family resemblance in their 

 voices. Listening to their various cries and calls, 

 the trained ear of the ornithologist can easily dis- 

 tinguish them and identify the species ; but after 

 years the image of the more powerful or the better 

 voices of, say, two or three species in a group of four 

 or five absorb and overcome the others. I cannot 

 find a similar case among British species to illustrate 

 this point, unless it be that of the meadow- and 

 rock-pipit. Strongly as the mind is impressed by 

 the measured tinkling notes of these two songs, 

 emitted as the birds descend to earth, it is not prob- 

 able that any person who had not heard them for 

 a number of years would be able to distinguish or 

 keep them separate in his mind to hear them in 

 their images as two distinct songs. 



In the case of the good singers in that distant 

 region, I find the voices continue remarkably dis- 



