162 BULLETIN 2 3, UNITED STATES NATIONAL MUSEUM 



TerritoTy. — Soon after their arrival on their breeding grounds the 

 males begin to select their territories and then to defend them. Dr. S. 

 Charles Kendeigh (1941) made a study of the territories of birds in 

 a prairie community in northwestern Iowa, and writes : 



A special study of the Yellow Warbler indicated that territorial requirements 

 included suitable nest-sites, concealing cover, tall singing posts, feeding areas Ib 

 trees, and space, and that when certain of these factors were lacking, territorial 

 relations became confused and the behavior of the birds was modified. * * « 

 These warblers possessed territories that averaged about 150 feet in diameter, 

 or approximately two-fifths of an acre. Even in locations w^here trees were 

 included, the territories appeared to be of about the same size. The limits of 

 the territory often did not coincide with the boundaries of the thicket in which 

 the nest was located but extended over the neighboring grassland and often in- 

 cluded parts of neighboring thickets. These territories were defended by the 

 males partly by singing, although in shrubby areas lacking trees they were handi- 

 capped by lack of singing posts from which to proclaim their ownership and to 

 advertise themselves. A few made use of fences from which to sing and also 

 of tall posts and wire from an abandoned electric line that extended through the 

 area. The role of the female in defense of territory was not determined. 



Probably due to this lack of singing posts and to the unusual abundance of birds, 

 chasing was also extensively used as a defense measure, and during the height 

 of the nesting season squabbling birds were a common sight all over the 

 area. * * * Neighboring males seemed to lack any conception of the limits 

 of each other's territories and moved about indiscriminately until chased out. 

 No actual fighting was observed. * * * In other parts of the area where 

 trees were available, the males commonly sang at a height of 18 feet, often up 

 to a height of 45 feet, and chasing was not often observed. 



For yellow warblers observed by Wendell P. Smith (1943) at Wells 

 River, Vt., "territorial exclusiveness scarcely existed. In one season 

 a Chestnut-sided Warbler's nest was located within five feet of that 

 of the Yellow Warbler. The following species were represented by 

 one nesting pair within a radius of thirty feet: House Wren, Cat- 

 bird, Black and White Warbler, Chestnut-sided Warbler, Northern 

 Yellow-throat and Indigo Bunting. Unless another individual came 

 very close to the nest, no hostility was shown by either male or female. 

 Too close an approach would bring a swift attack by one or the other, 

 however, but for only a short distance when the pursuer would give 

 up the chase." 



A. D. Du Bois mentions in his notes a nest that was about 6 feet 

 from the door of a screened porch in daily use and tells the following 

 story about the territory involved : "Twelve yards south of this nest 

 was a spruce tree. On several occasions the male met another male 

 at this tree or beyond it. Both alighted at times in the treetop. Their 

 boundary arguments had the appearance of pushing-contests in the 

 air; and sometimes the contestants revolved in the air, about an 

 imaginary axis between them. Once, while one of the warblers was 

 in the tree, the other was seen to poise near the tree on fluttering wings, 



