134 Tyler, Call-notes of Migrating Birds. L April 



breeds in large numbers to the north and northwest of us, that the 

 species breeds also in eastern Massachusetts (for even when we hear 

 the "x"' note most frequently, we find in this region no species 

 which have not bred here) and finally that its southward migration 

 through this vicinity is pretty well over by the middle of September. 

 I regret to say that, with all these data, I did not surmise the iden- 

 tity of the author of the "x" note until I saw and heard the note 

 uttered in the daytime by the Oven-bird. Then it seemed self- 

 evident that of all the possibilities, this species best supplied the 

 conditions. The discovery also explained the early disappearance 

 of our resident Oven-birds.^ 



It may appear strange that the Oven-bird should give its noc- 

 turnal call by da,>' (the call is distinctly different from any call 

 used by the young or adult of this species) but under certain con- 

 ditions, birds of several species add to their regular diurnal vo- 

 cabulary a note absolutely novel, and in a few cases I have been 

 convinced that they were using their migration call-note. Usually 

 the birds uttering these notes are migrants, — either birds like 

 Thrushes, remaining over a day or two between their night-flights, 

 or Warblers, flitting southward through the trees, continuing, as 

 they feed, their migratory progress. But birds about to migrate, 

 as well as those already under way, signal to each other in a like 

 manner. 



Perhaps the most familiar example of this phenomenon is fur- 

 nished by the Chipping Sparrow. Soon after the second brood of 

 young is fledged, our local Chipping Sparrows gather into families 

 or groups of a dozen or more. At this time, long before their 

 departure in October, we hear from our open windows a bird-note 

 which we have not heard during the early summer from the Chip- 

 ping Sparrows which have bred within hearing. It is a note which 

 to our ears suggests migration, both from its general resemblance 

 to the indefinite "chips" which many migrant birds utter as they 

 pass southward by day and by night, and also from the fact that 

 the note is usually given when the bird is in flight. " The Chipping 

 Sparrow utters this note only when flocking, and it ser^'es probably 

 to maintain the unity of the flock. The effect of the migration 

 calls, too, is to keep the companies together, but perhaps a more 



II have heard the "x" note only once in spring, — during the night preceding the 

 arrival of the Oven-bird in Lexington. 



