io6 EVOLUTION OF BIRD- SONG 



have heard it frequently uttered by nightingales 

 attending to the wants of their young. Other birds, 

 especially mimics, utter the cry in their songs ; but 

 the fact that in the nightingale it is addressed to 

 the young, and in the song has precedence of other 

 notes, indicates that it is the more natural to this 

 species. The yellow warbler of North America 

 (Dendroica cestivd) exhibits affinity to the willow- 

 warbler of Britain, not only in size, form, colour, and 

 habit, but also in voice. The song suggests the idea 

 that a willow-warbler is commencing his song, but 

 never attaining more than the first four or five notes. 

 The song is sometimes prolonged by one or two 

 notes, and then the resemblance to the willow-warbler 

 is even more apparent. I have observed many 

 yellow birds, both in Montreal and in Vancouver. 

 The female is exactly like the willow-warbler, but 

 has a faint light streak over the eye. The call-note 

 of this bird, young or adult, resembles that of the 

 young willow-warbler. 



The fact that alarms addressed by birds to 

 their young are practically invariable in character, 

 though varied in vehemence, leads one to conclude 

 that tewy is employed both as a call and as an 

 alarm by the nightingale. The alarm-croak of the 

 nightingale, so frequently uttered when the young 



