1030 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 2 



tree tops 20 to 25 feet above the ground in the spruce bog areas 

 along the Kuskukwim River in Alaska, and adds: "Where the tree 

 line disappeared, so did the juncos." 



Spring. — The migrating juncos rush across most of the eastern 

 and midwestern United States about mid-April passing, as they 

 go, their southern relatives already singing on their territories. In 

 Illinois M. C. Shank (1959) reports they build up fat reserves before 

 migrating, but D. W. Johnston (1962) finds the wintering popula- 

 tions leave Wake Forest, N.C., before they deposit any fat. The 

 birds are restless and hyperphagic, and move northward rapidly in 

 flocks of up to 100 individuals. In the East they are often accom- 

 panied in the earlier part of the migration by fox and tree sparrows; 

 later along the Saskatchewan River they may be accompanied by 

 tree and clay-colored sparrows (Houston and Street, 1959). 



Territory. — The males usually arrive on the breeding grounds well 

 in advance of the start of nesting. During 10 years of observation 

 near Olean in southwestern New York State (Eaton, 1965) I heard 

 the average first territorial singing on March 12, but most males 

 here do not start their territorial song in earnest until about March 

 21. Some 300 miles farther north Mrs. L. de K. Lawrence writes 

 (in litt.) the juncos arrive at her home in Rutherglen, Ontario in 

 late March or early April, with a mean arrival date of April 2 for 

 13 years. 



The male proclaims his territory by singing from the top of the 

 taUest trees within it, which may be 50 to 75 feet above the ground. 

 Nero (1963) writes from the Lake Athabasca, Saskatchewan region: 

 "On May 18 I found two males apparently engaged in a territorial 

 dispute. The aggressor approached with its breast feathers raised 

 and spread, forming a broad front, and with its tail widely spread 

 and alternately depressed and elevated. Its pinkish bill was very 

 conspicuous against the dark feathers of the head." 



Individual territories appear to vary greatly in size, probably 

 because of the scarcity of choice nest sites. The area a male defends 

 vigorously has never been determined experimentally with models 

 and recorded songs, but casual observations of the location of song 

 perches near Olean suggest it is about 2 or 3 acres. Where ideal 

 nest sites are more plentiful, the territories are probably smaller. 

 Each usually seems to include some sort of opening in the forest 

 canopy surrounding a rock outcrop or an exposed soil bank. The 

 species' tendency to build in or near some sort of vertical wall prob- 

 ably helps to explain many unusually placed nests. 



Courtship. — The male may continue to sing for some days before 

 a female enters his territory. Mrs. Lawrence (1956) thus describes 



