NATURAL HISTORY OF THE SWAINSON'S WARBLER 69 



of song during incubation appears to be to let the female know 

 of her mate's whereabouts. I assume this, since the incubating 

 female, upon leaving the nest, often goes to the male, with whom 

 she feeds. 



Singing during the nestling period is sporadic, since the male 

 assists in the feeding of the young ; after the young leave the nest, 

 apparently only the female attends them, and the male increases 

 his singing. During a 2-hour period (10:30 a.m. to 12:30 p.m.) 

 when a Dismal Swamp female v^as attending her fledglings, the 

 male sang a course about once every 10 minutes. After destruction 

 of its mate's first nest, another male sang vigorously throughout 

 the day and moved about the territory much more than usual; 

 the female became very quiet and avoided the male, although she 

 remained in the territory. 



Daily pattern 



The daily singing schedules of the Swainson's Warbler and 

 other passerine woodland birds are about the same. In the Ocmul- 

 gee River forest the first singing of the Swainson's Warbler and 

 other woodland birds was noted on a mild, cloudy morning, April 

 14, 1966. Sunrise was at 6 :07 a.m. The first bird that sang was a 

 Cardinal at 5 :25 a.m., followed by a Rufous-sided Towhee at 5 :32, 

 a White-throated Sparrow (Zonotrichia alhicollis) at 5:33, a 

 Wood Thrush (Hylocichla mustelina) at 5:35, and then two 

 Swainson's Warblers at 5:47. The Swainson's was the first war- 

 bler to sing, follov^ed by a Prothonotary Warbler at 5 :55 a.m. and 

 a Hooded Warbler at 5:57 a.m. Almost all species of woodland 

 birds were singing by 6 a.m. 



In one of my study areas in the Dismal Swamp on June 3, 1966, 

 the first Swainson's Warbler sang at 4:27 a.m., following a 

 Cardinal, Wood Thrush, Wood Pewee (Contopus virens), Crested 

 Flycatcher (Myiarchus crinitus), Hooded Warbler, and Tufted 

 Titmouse (Parus bicolor), all of which began singing after 4:05 

 a.m. Sunrise was at 4 :44 a.m. 



On April 14, 1966, in the Ocmulgee floodplain forest, two 

 Swainson's Warblers v^ith adjoining territories stopped singing at 

 7 and 7 :14 p.m. On June 2, 1966, in the Dismal Swamp, a Swain- 

 son's Warbler sang until 6:45 p.m. Only the Wood Thrush, 

 Cardinal, and Wood Pewee sang later in that section of the woods. 

 Sunset was at about 7:28 p.m. 



Rate of singing 



A song is sung in a course or series, that is, a period of steady 

 singing for several minutes at a time. Sometimes in the early 



