EVOLUTION OF BIRD- SONG 



having been robbed, he afterwards uttered only one 

 or two dismal notes at long intervals. I knew the 

 song of this bird very well ; and afterwards, in the 

 same season, when listening to other nightingales, I 

 soon learned the well-known fact that these birds, 

 like many others, differ individually in their songs 

 and times of singing. During the next few years 

 I found no inducement to attempt any deliberate 

 investigation of the songs of birds; but in 1885 

 the subject was again brought prominently before 

 me. A thrush of very remarkable vocal powers 

 had its nest in our garden, and sang every day in 

 a high acacia-tree not far from the house. At that 

 time I was much at home nursing a sick relation, 

 and in these circumstances the loud clear song of 

 the thrush was particularly noticeable. Towards 

 the end of May we observed that on every success- 

 ive morning the bird began to sing about a minute 

 and a half earlier, so that we could predict almost 

 to a minute the time when his first notes w^ould be 

 heard. His extraordinary endurance led me to 

 record his periods of song, with the astounding 

 result that these on one day amounted to an 

 aggregate of no less than sixteen hours, thus 

 allowing only three hours of silence during the 

 whole time of song, which extended from 2.45 



