138 Tyler, Call-notes of Migrating Birds. [April 



diurnal note of Dendroica striata, viz. "tsit." On account of this 

 correspondence and from the fact that at this season, Black-polls 

 are passing through Eastern Massachusetts in numbers which at 

 times seemingly svn-pass all other birds combined, I think it is no 

 unfair assumption to ascribe this, the commonest note of autumn, 

 to the Black-poll Warbler. As the season advances, many of the 

 notes are more sustained than the abrupt "chips" which suggest 

 the warblers, and resemble the "tseep" note which is used in the 

 daytime by several of the smaller sparrows. These notes become 

 progressively more frequent, reaching their maximum abundance, 

 perhaps, toward the middle of October, and are the last notes 

 heard in the autumn before the migration ceases. That these 

 notes represent the passage of various species of Sparrows, I think 

 there is little doubt. The frequent occurrence of these notes 

 during the evening of March 28, 1908, at the height of the sparrow 

 migration that spring increases the probability. As to the identity 

 of many other notes heard during this period, I do not hazard even 

 a guess. As an indication of the real individuality of some of the 

 nocturnal bird-notes and of the actual ability of an observer to 

 distinguish between them, I may say that during the remarkable 

 flight of Cape May Warblers which passed through this region in 

 September, 1914, I heard a note absolutely novel to me. I heard 

 it before I saw any of the Cape Mays and of course had no idea what 

 it was until I noticed that the Cape May Warblers used this note 

 when they flew from tree to tree. 



The migration note of the Bobolink is diagnostic; it is used by 

 day as well as by night, but in my experience it is rarely heard at 

 night, although it is a common note in the very early morning, 

 after daylight, when the birds may be seen flying in flocks. My 

 explanation of the rarity of this note at night is that the birds 

 generally fly so high that their notes are nearly or quite inaudible 

 from the ground. At other observation stations the Bobolink's 

 note may, very likely, be heard more frequently. I was fortunate, 

 one spring, to see numbers of Fox Sparrows start on their night 

 flight soon after sunset. The birds flew northward, at first from 

 one tree to another, uttering, while in the air, a note not dissimilar 

 from one of their sibilant "chips." I heard this note that evening 

 from birds flying through the darkness against a cold northwest 



