NATURAL HISTORY OF THE SWAINSON'S WARBLER 83 



morning. Songs are given in courses or series. The rate of singing 

 is usually faster at the beginning of a course. The number of 

 songs sung by a territorial male in 1 day, June 3, in the Dismal 

 Swamp was 1,168. It produced 186 songs the first hour and sang 

 at a fairly constant rate from 5 to 8 a.m., 192, 194, and 198 songs 

 per hour. 



Muted or whisper songs are a continuous chatter that may go 

 on for as long as 3 minutes. They do not resemble the primary 

 advertising song and may be given in the presence of other 

 Swainson's Warblers or when alone. The alarm note is a sharp 

 chip. A weaker chip is used for communicating during courtship. 



The primary advertising song is sung from the ground and 

 from perches at low elevations. The whisper song is- usually given 

 from the ground. 



The Swainson's Warbler is primarily a ground feeder, but 

 sometimes searches for food a few feet above the ground in under- 

 growth. Insects, its main food, are located as the bird pokes its 

 bill under leaves, pushing them upward and examining the under- 

 side, and searching the ground beneath. Foods gleaned from 

 beneath the leaf mantle usually are ground beetles, crickets, ants, 

 and spiders. Sometimes caterpillars are taken in the course of 

 foraging in the shrub strata. 



The usual gait of the Swainson's Warbler is a cross between 

 a hop and a walk, suggesting a canter. The direct method is used 

 in head scratching, that is, bringing the foot forward and under 

 the wing. Tail spreading or fanning by a male may occur follow- 

 ing a territorial boundary dispute with another male. 



The Swainson's Warbler is one of the least abundant of south- 

 ern warblers. It has a low nesting success because its large bulky 

 nest is poorly concealed, is located close to the ground, and con- 

 tains white eggs. In parts of its range it is highly parasitized by 

 the cowbird. In some Coastal Plain floodplain forests, nests are 

 destroyed during floods. 



