14 OUR FAVOURITE SONG BIRDS 



and war. Rival males sing at each other, chase 

 each other from tree to tree or through the 

 branches, fight fiercely, and sometimes seem so 

 lost in their ecstatic rage as to be utterly oblivious 

 to their own personal safety. Birds have been 

 known actually to die under the violent exertions 

 of song that a rival has inspired. Robins, to take 

 a homely instance, often get so excited whilst 

 singing against a rival that their song breaks into 

 harsh sounds which are nothing but screams of 

 defiance. We have often watched rival males of 

 this species gradually approach each other singing 

 at intervals between each stage of their progress, 

 and then finally engage in combat. Mild tempera- 

 ture and abundance of food may be a strong 

 incentive to song, but only indirectly as these 

 conditions affect the sexual impulses. 



Another branch of this interesting subject which 

 the student must not fail to notice is the very 

 perceptible amount of Variation in the songs of 

 individuals of the same species. This is a very 

 difficult study, for it requires a fine musical ear and 

 some training ; and yet it is one that has hitherto 

 received little attention, although a most promising 

 and pleasing field of inquiry. We have repeatedly 

 remarked variation in the songs of the same species 

 in widely different localities, especially in the notes 

 of some of our common birds in Algeria. Captain 

 S. G. Reid states that the resident Chiffchaffs in 



