82 



NORTH AMERICAN FAUNA 69 



Virginia, April 20, 1958. Brooks and Legg counted 10 or 11 sing- 

 ing males along 1.5 miles of Franzy Creek in Nicholas County, 

 W. Va. 



The Swainson's Warbler is 5 to 51/2 inches in length, and during 

 the breeding season weighs about 15 grams. Breeding birds of 

 the Southern Appalachians usually have whiter underparts than 

 Coastal Plains birds. 



The Swainson's Warbler is one of the last of the southern 

 warblers to arrive on the breeding grounds, but is earlier than 

 most northern transient members of the family. One banded male 

 returned to the same territory in Maryland for five consecutive 

 breeding seasons. 



Nine territories ranged in size from 0.3 to 4.8 acres. The size 

 and shape of a territory varies during different phases of the 

 breeding cycle. 



Hostile encounters between neighboring males usually take 

 place along territorial boundaries. Paired males usually initiate 

 border encounters with unpaired males. A display is sometimes 

 performed by an aggressive male after it is driven back into its 

 territory. 



During courtship and mating the male sings very little. Fre- 

 quently he flies to the female, who usually is foraging on the 

 ground, and either pecks at her rump or pounces on her. Copula- 

 tion sometimes takes place during pouncing. 



First nests usually are built by the first week in May. Although 

 other investigators reported finding nests outside the defended 

 territory, all nests that I found were within the territory. The 

 large bulky nest of this species is usually placed 2 to 6 feet above 

 the ground. It is built by the female from materials gathered 

 close to the nest site ; she takes 2 or 3 days to complete it. 



Three and occasionally four white eggs are laid. At a Dismal 

 Swamp nest the incubation period was 13 days. The cowbird 

 parasitizes nests in some parts of the breeding range. 



During incubation two females spent 54 and 78 percent of day- 

 light time on the nest. Both sexes feed young and clean the nest. 

 Young remain in the nest 10 to 12 days. Fledglings of one brood 

 were attended only by the female. 



The song of the Swainson's Warbler is loud and ringing and of 

 marked musical quality. It consists of three or four high intro- 

 ductory notes, all separated, followed by a phrase of four or five 

 syllables uttered rapidly, and slurred. Songs are delivered at a 

 rate of about 8 or 9 per minute for the first few minutes of morn- 

 ing song, then decrease to 5 or 6 per minute for most of the 



