434 NORTH AMERICAN BIRDS. 



They are not, however, to be regarded as nocturnal, as they are only known 

 to do this during a brief period. 



The nest of this species is a very peculiar and remarkable structure. It 

 is composed of small twigs of nearly uniform size, wrought and interwoven 

 into a neat semicircular basket. In selecting the twigs with which they are 

 to construct their nests, the Swifts break from the tree the ends of living 

 branches, which they gather with great skill and adroitness while on the 

 wino-. Sweeping upon the coveted twig somewhat as a Hawk rushes on its 

 prey, it divides it at the desired place, and bears it off to its nest. This is 

 a well-attested fact, familiar to all who have ever watched these birds in 

 the early morning as they are at work constructing their nests. 



Each one of these twigs is strongly fastened to its fellows by an adhesive 

 saliva secreted by the bird, and by the same cement the whole structure is 

 made to adhere to the side of the chimney in which it is built. This saliva, 

 as it dries, hardens into a tough glue-like substance, as firm even as the 

 twigs it unites. In separating nests from the sides of chimneys, I have 

 known portions of the brick to which it was fastened part sooner than the 

 cement. When moistened, liowever, by long-continued rains, the weight of 

 their contents will sometimes cause these nests to part, and the whole is 

 precipitated to the bottom. The young birds cling very tenaciously to the 

 sides of the chimneys with their bills and claws. They not only are often 

 able, in these accidents, to save themselves from falling, but even at a 

 very early age can cling to the sides of the chimney and work their way 

 to the top. They always leave their nest and climb to the upper part of 

 the chimney several days before they can fly, and are there fed by their 

 parents. 



Occasionally the young birds fall to the bottom of the chimney, out of the 

 reach or notice of their parents. I have never been able to induce them to 

 take any food, although they keep uttering pitiful cries of hunger. In such 

 cases the young birds placed on the roof near their native chimney soon 

 manage to climb to its base, and there receive the aid of the old birds. 



Their eggs are four in number, somewhat elliptical in form, though some^ 

 what less obtuse at one end than the other. They are of a pure white 

 color, and are never spotted. They vary but little in size or shape, and 

 measure from .75 to .81 of an inch in length, and from .50 to .55 in breadth. 



In New England the Chimney Swallow raises but one brood in a season. 

 In Pennsylvania it is said to have two. 



