TREE SPARROW 1143 



The size of individual territories was found to vary with the season 

 and the location. Dunng the first week in June, when birds were 

 engaged chiefly in feeding together, courting, and preliminary building, 

 territories were large and poorly defined. One male, feeding with his 

 mate at a little pool, made vicious attacks upon a thh-d bh-d and 

 pursued it 400 to 500 feet before circling back. Then abruptly the 

 pair flew K mile downstream and disappeared in the brush. 



With the onset of incubation, areas became more limited. Isolated 

 nest I was surrounded by a territory some 600 by 700 feet in diameter, 

 and both birds frequently fed and later obtained food for their young 

 at a drainage ditch 450 feet from the nest. In the more congested 

 thicket occupied by nests III-VI, the song perches of the various 

 males encompassed territories only 200 to 300 feet in diameter. 

 Occasional overlaps occurred without friction, provided the other 

 male was singing at the opposite side of his territory; and in spite of 

 close quarters very little fighting was observed. 



"While the young were in the nest, both parents foraged in the thick 

 tangle of low leafy branches of the tiny birches and willows, frequently 

 only 10 or 15 feet from their charges. Throughout the latter part of 

 July 1934, the gay plumes with vrhich the adults were marked waved 

 from the same tiny territories while the fledglmgs scuttled among the 

 underbrush. 



During early August, when the young were fuUy fledged and able 

 to feed themselves, the three 1934 broods in this area ranged freely 

 throughout the 300- by 500-foot patch of thicket, though they still 

 maintained family unity. Not imtil the 19th of August did they 

 emerge from the thick cover and merge with the flocks that were 

 gathering in the grasses and moss of the river flats. 



The main defense of territory against invasion is song, strengthened 

 by an occasional brisk assault upon an intruder. While this is 

 usually by the male, his mate occasionally assumes the offensive. At 

 nest I when the young were a day old, the brooding female suddenly 

 darted from the nest and made a vicious attack upon another tree 

 span-ow. At nest IV the incubating female flew at a yellow warbler 

 that perched carelessly some 20 feet from her— her mate was singing 

 only 150 feet from the nest, but she apparently considered the case 

 too urgent to wait for him to expel the trespasser. 



At my intrusion the parent birds chipped anxiously, but neither 

 attacked, as will hawks, terns, owls, and jays, nor feigned injury as 

 did their neighbors the shore bu'ds, though if followed they would 

 guilefully lead me farther and farther afield. The chief protection of 

 the incubating female was her streaky coloration, which she rehed on 

 until almost stepped upon. 



