346 BULLETIN 191, UNITED STATES NATIONAL MUSEUM 



excavate their own burrows and select certain hardwoods or pines that 

 are soft ; but often peach and cjierry stubs are used, and these have very 

 hard outer bark. Dickey (MS.) Hsts 17 species of trees, all hardwood, 

 that are used by carolinensis ; to these the writer could add several pines 

 and the peach. Woodpecker holes are sometimes used, as well as ' 

 natural cavities in dead or live trees. Dickey writes that he has "known j 

 them to build in iron pipes used for clothes lines, pipes to support i 

 bridges, small bird houses, etc." 



Both sexes excavate, but the female probably does the most in nest 

 construction. The average height of the nest above the ground would 

 be about 5 or 6 feet. Dickey mentions 1 foot as the minimum distance ; 

 from the ground, while Erichsen's (1919) 22 feet must be considered ' 

 the maximum. i 



According to Dickey, two weeks are required on an average to com- | 

 plete a burrow, but obviously this would depend on the depth of the ! 

 excavation and the softness of the wood. In a peach stub, for example, | 

 after the hard shell has been pierced, the going would be easy. On the | 

 other hand, oak would be consistently harder to excavate. The same { 

 observer gives average measurements of the completed burrows and i 

 entrance holes, as follows: 



Diameter of aperture 1^ inches 



Depth of cavity 5 inches 



Width of cavity at aperture 2 inches 



Width of cavity at nest enlargement 2}i inches 



When the hollow has been excavated, nest-building is begun, as Dickey 

 says, "with thicjc foundation of moss (Hypnum) — strips of yellow and 

 brown bark, a few strips of yellow grass and grass culms or panicles, a ' 

 little thistle down or milkweed pod down, and then such bird feathers as 

 those of sparrows, bluebird or of the parent. The cup is well padded 

 with silvery milkweed or thistledown, animal hair, red hair of the cow, 

 gray fur of the cottontail rabbit and fur also from deer, mice, and other 

 Mammalia." 



Erichsen (1919) writes: "Simultaneous with the appearance of the ' 

 down on the stalk of the cinnamon and royal ferns, which occurs during 

 the middle of March, the chickadee begins nest-building, for this ma- ! 

 terial is used largely by the birds in lining their nests. As far as my 

 observations go, the birds, in gathering the down, always begin at the 

 top of the stalk and work downward. The green moss that collects on 

 the trunks of certain species of hardwoods is also used to a considerable 

 extent, being always placed in the nesting hole first, and upon it the t 

 down is deposited." 



