THE EVOLUTION OF BIRD-SONG. 239 



such repetitions slightly varied in pitch. The songs of the 

 Chaffinch, Greenfinch, Goldfinch, House Sparrow, Linnet, Blue 

 Titmouse, Great Titmouse, Coal Titmouse, Yellow Bunting, 

 Swallow, and Jackdaw contain little more than such repetitions ; 

 and the Starling, Wren, Meadow Pipit, and Sky Lark frequently 

 introduce into their songs their respective call-notes. In the songs 

 of the Grasshopper Warbler, Willow Warbler, Wood Warbler, 

 Bedstart, and Nightingale also there are traces of the construction 

 of phrases by repetition of single cries. The arbitrary phrases 

 were probably further developed by the imitativeness of the birds 

 which attempted to reproduce surrounding noises with which they 

 were familiar; and we can find evidence of this modulation in the 

 present songs of many birds. The prevalent long, hooting cries 

 of the StrigidcB are like the howls of wolves, and also resemble 

 the moaning and whistling of wind in holes in trees or rocks, 

 the favourite nesting-places of these birds. The shrieking cry of 

 the Swift suggests the " swish" of its wings in swooping, or eager 

 pursuit of its fellows : the Swallow and Martin do not scream, 

 nor have they the pursuing habit of the Swift. The Dipper 

 sings, like his solitary companion, the Wren (Yarrell's * British 

 Birds,' 4th edit. vol. i. pp. 174—176). The call of the latter, 

 as already stated, resembles the note of the hedge-cricket. 

 The song of the Redbreast seems to be, in its general character, 

 an imitation of the gurgling of water : in summer the bird is 

 very often near water. The "crake" of the Landrail is in time 

 and tone closely like the noise made by the grazing of a cow.* 

 The sibilant phrase of the Wood Warbler reminds us of the 

 frictional sounds made by branches that rub against each 

 other. The Grasshopper Warbler has modified and extended 

 the same phrase to a resemblance of the cry of the field-cricket. 

 The " quack" of the Mallard is like the croak of frogs. Many 



* Cattle when grazing protrude the tongue from each side of the mouth 

 alternately, each time round a bunch of grass, which is torn off. A pause 

 then occurs during the act of swallowing, after which the tearing is resumed. 

 The consequence is a sound which may be thus expressed, " rasp rasp — rasp 

 rasp — rasp rasp." Cattle graze more at night than in the daytime ; and 

 the Landrail is to a great extent nocturnal, and although the feeding- 

 grounds of cattle are not the nesting-places of this bird, it is frequently 

 within ear-shot of grazing, the sound of which is particularly noticeable 

 at night. 



