WHITE-THROATED SPARROW 1371 



in the rest of the habitat. Comparison of this character for nest 

 sites of the three species of sparrows studied showed that white-throats 

 tend to select nest sites in areas exhibiting a degree of clumping of 

 objects intermediate between the singly arranged objects about song 

 sparrow nests and the dense clumping about junco nests. 



Thus white-throated sparrows apparently select their nest sites 

 in relation to the amount and dispersion of the nearby cover. As 

 the species chooses conditions intermediate between the open areas 

 in which song sparrows nest and the dense woodland in which juncos 

 nest, the nesting habitat may be described as forest edge. 



Eggs. — The white-throated sparrow lays from 4 to 6 slightly glossy 

 eggs. They are ovate with some tending toward elongate ovate. The 

 ground is creamy, bluish, or greenish white, and heavily marked with 

 speckles, spots, and blotches of reddish browns such as "natal brown," 

 "Verona brown," "Mars brown," "russet," and "chestnut." They 

 vary considerably, often the ground is entirely obscured giving the egg 

 the appearance of being light brown with cloudings and spottings of 

 the darker browns; others may show a considerable amount of the 

 greenish ground with bold blotches of the dark browns, and on these, 

 undermarkings of "pale neutral gray" may be seen. The eggs are 

 practically indistinguishable from those of the white-crowned sparrow 

 except that they average slightly smaller. The measurements of 50 

 eggs average 21.0 by 15.4 millimeters. The eggs showing the four 

 extremes measure 23.3 by 15.1, 21.6 by 16.8, 18.8 by 14.7, and 21.3 

 by 14-2 millimeters. 



The average of 41 clutches found over a two-year period in Algonquin 

 Park was 4.1 with a range of 3 to 5 eggs. Houston and Street (1959) 

 report an exceptional clutch of 7 eggs from Cumberland House, 

 Saskatchewan. A few observations on renests in Algonquin Park 

 showed no change in clutch size with time of year. Two observations 

 of females carrying nesting material after the first eggs were laid 

 suggest that egg-laying starts before the nest is completed. 



Incubation. — Only the female white-throated sparrow incubates, 

 as many authors (e.g. Knight, 1908; Forbush and May, 1939) have 

 reported, and which our observations on color-banded birds in Algon- 

 quin Park confirmed. One egg is laid per day until the clutch is 

 complete, but it is not known when incubation begins. Five observa- 

 tions of nests in Algonquin Park suggest that the eggs are laid early 

 in the morning. 



Once incubation has started, it is possible to approach to within a 

 few feet — in some cases 2 or 3 feet — of the incubating bird, before she 

 takes flight. Unless the observer stops or vigorously disturbs the 

 vegetation, the female may remain on the nest. Once flushed she 

 either flies directly to the nearest clump of bushes, or runs along the 



