The Sieging of Birds, S.P.BickneH. 



Turdus mustelinus. Wood Thrush. 



This most admirable song-bird is in voice from its arrival, in 

 late April or early May, until about the middle of August. But 

 towards the end of July singing becomes less universal with 

 membei s of the sjaecies, and soon after has come to be inconstant 

 and confined to the earlier and later hoiu's of the day. Songs 

 are usually to be heard througli the first week of August, and 

 sometimes for a week later (August 6-15), when singing some- 

 what abruptly ceases, seven or eight weeks before the final depart- 

 ure of the species.* 



After the cessation of singing these Thrushes become shy and 

 inactive, affecting the most retired parts of the woods, and only 

 the careful observer will discover that they have not disappeared. 

 Even their call-notes almost liave been discontinued, and when 

 heard are so low in tone and so brief as almost to seem as if 

 accidentally uttered. Before their departure, however, though 

 they do not again sing, voice is partially regained ; and in October, 

 even so late as the middle, or rarely last of the month, their call- 

 notes may sometimes be heard uttered with the same vehemence 

 as in the spring. 



The suspension of song by this bird during two months preced- 

 ing its departure can be accounted for, according to the probabili- 

 ties earlier adduced, by physiological activities antagonistic to 

 song operating during that time. In late August adults are 



covered with growing feathers and without fat. In mid-Septem- 

 ber some, at least, show a nearly perfected plumage, with areas 

 of fat beginning to accumulate ; and individuals may be found 

 almost a month later with the renewal of plumage still incom- 

 plete ; such, perhaps, are birds of the year. It would appear 

 from these facts that the impulse to song is first interrupted by 

 the moult, and further suppressed by the supervening adipose 

 condition. 



Auk, I. April. 1884. p. /Xff-f-l'^ 



*An exceptionally late date for song is August 23, 18S3. On tliat day I for some 

 minutes listened to the singing of a Wood Tlirush wiiich was of a very unusual charac- 

 ter. Though all the notes of the normal song were given, they were so faintly uttered 

 and separated by such distinct pauses, as to make it seem probable that they resulted' 

 from the first trial of a young liird. 



