NATURAL SCIENCES OP PHILADELPHIA. 107 



during the early part of Ma3^, about the time the horse chestnut 

 (jEscuhis hi];)pocastanum) spreads its rich clusters of fragrant 

 blossoms to the vernal breezes. The small insects which frequent 

 the blossoms for their honey, together with the honey itself, afford 

 it a rich repast. It commences building during the early part of 

 June, both birds working assiduously until the nest is completed. 

 In the spring of 1812, Master Charles Silverthorn, one of the 

 writer's pupils, secured for the latter's collection at least fifteen 

 nests, from a district scarcely one-fourth of a mile in diameter, 

 thus showing the abundance of the species in this latitude. Some 

 of these nests were saddled upon the moss-covered branches of an 

 apple or pear tree, while the major part of them was found upon 

 the branches of various species of oaks, chiefly Quercus rubra and 

 Quercus alba. They were constructed of a W00II3' substance of 

 vegetable origin, plucked from the leaves of Verbascum thapsus, 

 L., of almost immaculate whiteness. It is doubtful whether the 

 soft down which appears upon the unexpanded leaves of the pop- 

 lars is utilized, since the leaves are already developed in the gene- 

 rality of cases when nidification commences. The exterior of the 

 nest is compactly covered by a thatching of bluish-colored lichens, 

 possibly a Parmelia, glued thereon by a viscid saliva, secreted by 

 the birds. I have never observed, as some, the small woody fibres 

 on the outside, which are said to strengthen the fabric. Occasion- 

 ally a few cobwebs have been noticed, but the manner in which 

 the lichens cohere seems to be all that is necessary. The nests are 

 usually 1.50 inch in diameter, with a depth of 1.75 inch. Speci- 

 mens have been taken fully 2 inches in ' depth. The internal 

 cavity never exceeds | of an inch in depth, while instances are 

 known of small nests with less than ^ inch. The writer has taken 

 nests during the latter part of Juh*, with eggs, but whether a 

 second set or not he is unable to say, possibly the work of pairs 

 that have been frustrated in their labors during the earl}^ part of 

 the season. During the hatching period the male is in close 

 proximity to the nest, and if any attempt is made to interfere 

 therewith, is foremost and loudest in his cries of resentment, and 

 even flies into the intruder's face with half opened jaws, requiring 

 considerable effort to beat him off. His mate is of a more passive 

 nature. The period of incubation, according to the writer's esti- 

 mate, is about eight days. So susceptible to cold is the species 



