96 EVOLUTION OF BIRD- SONG 



the mere purpose of making a noise — probably to 

 attract attention. It is heard in a slightly abbrevi- 

 ated form as an alarm uttered by the common 

 thrush when the nest or the young are threatened 

 by a predacious beast or bird ; but, apparently, 

 upon no other occasion. Mr. Warde Fowler con- 

 siders that the alarms of blackbird and of ring-ousel 

 are generically similar, but specifically distinct {in 

 litt). Mr. Harting says of this species : " When 

 on the wing, its note has been compared to the 

 noise made by striking two large stones together" 

 {Birds of Middlesex^ p. 36). Bechstein wrote that 

 the bird calls tak like a blackbird {Nat. Hist. Cage 

 Birds, p. 201). The fieldfare utters a somewhat 

 similar alarm and call -note, which Mr. Harting 

 renders tcha- cha-cha {Birds of Middlesex, p. 30). 

 The blackbird's rattling alarm, more musical than 

 that of the mistle- thrush, is familiar to all dwellers 

 in the country. It is much modulated in different 

 individuals. Layard says of the South African 

 olivaceous thrush {Turdus olivaceus), when alarmed 

 and hurrying off, " its voice and manners reminding 

 an observer of the European blackbird " {Birds of 

 South Africa, p. 201). The strong family re- 

 semblance between the rattling alarm-cries of the 

 mistle -thrush, thrush (when defending its young), 



