NATURAL HISTORY OF THE SWAINSON'S WARBLER 47 



Figure 20. — Overlapping territories occupied by the same (marked) male 

 Swainson's Warbler for three successive years (1966, 1967, 1968) in the 

 Dismal Swamp in Virginia. 



Territories 



Males establish territories soon after arrival on their breeding 

 grounds. The size and distribution of territories in an optimum 

 area may depend upon the extent and arrangement of the habitat, 

 as well as upon competition with other male Swainson's Warblers 

 for food and space. Where prime habitat is limited in extent, it 

 may support several territories, thus creating a group or "colony" 

 of birds. This situation frequently occurs in southern canebrakes 

 and is not unlike breeding "colonies" of the Kirtland's Warbler 

 (Dendroica kirtlandii) in Michigan jack pine (Pinus Bankisiana) 

 habitat. In a 7-acre canebrake in the Ocmulgee River floodplain 

 forest near Macon, Ga., there were four territories, and not all 

 of the canebrake was occupied. 



Sprunt and Denton (in Griscom and Sprunt, 1957 p. 51) re- 

 ported that four territories in Georgia ranged in size from 0.72 

 to 0.91 acre (table 2). Two of the territories were adjacent and 

 two were not. The smallest territory that I measured at Macon 

 contained only 0.3 acre (table 2). It was in a block of woodland 

 approximately 2 acres in size and was separated from the main 

 forest by a cleared powerline right-of-way 50 yards wide. 



In the Dismal Swamp, prime habitat is spotty; the territories 

 are farther apart and larger than in the Ocmulgee River flood- 

 plain forest, where optimum habitat often occurs in larger blocks. 

 The territory of one paired male in the Dismal Swamp covered 



