NATURAL HISTORY OF THE SWAINSON'S WARBLER 73 



most like the chip of the first or last note of the song of the White- 

 eyed Vireo. The two species occur together in the Coastal Plain 

 Province, and I often have been fooled by the Vireo. However, it 

 is not long before the Vireo reveals its identity as it follows through 

 with the rest of the song or starts singing after giving the sharp 

 chip note. Brooks and Legg (1942, p. 83) thought the Swainson's 

 Warbler chip similar to that of the Mourning Warbler. 



The chip call is used during intraspecific territorial strife, 

 when alarmed by such nest robbers as snakes. Blue Jays (Cy- 

 anocitta cristata), and Common Crackles, and as a call-note for 

 members of a pair. 



A variation of the chip note is used by the female during the 

 mating period (see section on Courtship and Mating). In this 

 case the notes may be softer and more musical, and they are run 

 together, almost forming a chatterlike song. 



Another vocalization uttered by both sexes resembles the zeep 

 note of various species of warblers during fall migration. I have 

 heard Swainson's Warbler give this note in September when still 

 on the breeding territory. On April 28 in the Dismal Swamp, 3 

 days before nest building, I heard a female utter a soft zeep each 

 time her mate sang. The note was so weak and the male so far 

 from her that I am sure he seldom heard it. 



