54 EVOLUTION OF BIRD-SONG 



herited simple song of the tinamu. Rhynchotus 

 rufescens, he says, has a song or call " heard oftenest 

 towards evening, which is composed of five modulated 

 notes, flutelike in character, very expressive, and 

 uttered by many individuals answering each other as 

 they sit apart concealed in the grass." This appears 

 to be an invariable strain, frequently employed, and 

 transmitted to the young by inheritance. In some 

 birds the call-note is extended, as it is by the 

 nuthatch, which prolongs its full -toned short cry 

 tewit in the production of a loud mellow whistle 

 slurred upward in about the interval of a fifth. It 

 may be whistled slowly thus : 



Smorz. 



About March, April, and the beginning of May, 

 the skylark nearly always concludes its song, while 

 descending from the sky, with a repeated plaintive 

 whistle, which descends in pitch, and at this season 

 is often uttered during the phrase. This cry is 

 hardly to be distinguished from the call of the 

 young skylark, and may be whistled slowly thus : 



Later in the season the bird soars less when 



