430 Hawkins, Sexual Selection and Bird Song. [o"t. 



of cases there is only one ardent male bird in the presence of the 

 female and he is often the bird with which she has already mated. 



A weakness of the sexual selection theory that has not been 

 given sufficient consideration is that the song of birds has been 

 treated too exclusively in connection with the mating season. 

 Men have riveted their attention on those rapturous bursts of song 

 which precede and continue through the mating time, and have 

 given too little attention to the fact that few birds are ever wholly 

 voiceless, that most birds speak the sign or voice language, at least 

 to some extent, all through the year. 



Most of our best singers have two distinct song periods. One 

 begins with the arrival of the advance guards of the migrating 

 hosts and continues until the broods of young birds are hatched. 

 When the young birds have left the nest and are able to care for 

 themselves there is a cessation of the full, joyous songs, September 

 being generally the silent month. Then many of the birds begin 

 to sing the last of September or the first of October and continue 

 until November. Bicknell has determined definitely the limits 

 of these song periods for many of our birds. The House Wren 

 begins to sing its love song in April and continues to the last of 

 July or the first of August. After a period of comparative silence 

 it begins its autumn song which has none of the spontaneity of the 

 spring song but consists of a "low rambling warble" which con- 

 tinues to the middle of October. The Black and White Creeping 

 Warbler sings from April to the late June. Its second period begins 

 from the ninth to the twenty-second of August and lasts only a few 

 days. The first period of the Oven-bird stops by the end of June. 

 The second period begins in August, at first haltingly, as though 

 it had forgotten how to sing, but finally bursts into full song by 

 October. The Wood Thrush sings from its arrival in late April or 

 early May until the middle of August. It is not heard again until 

 October and then only the call notes, never the full song. 



Bicknell attributes this period of silence to the moult of the bird. 

 In many cases the moulting periods of our song-birds correspond 

 more or less closely with periods of silence, voice being, renewed 

 with the renewal of plumage. The general statement may there- 

 fore be made, that birds are predisposed towards silence during the 

 height of the moult. Though this fact may by many be regarded 



