OF EASTERN PENNSYLVANIA. 39 



ceus, and like the same is rudely constructed, but 

 lacks its compactness. In "North American 

 Birds" by Baird, Brewer, and Ridgway, it is posi- 

 tively affirmed that the "base is usually made of 

 coarSe twigs, sticks and end^ of branches, firmly 

 interwoven." 



A fair sample which we have beside us, and 

 which may be considered as the normal type in 

 our latitude, presents considerable variation, 

 Dry leaves of Quercus, Fagus and Castanea 

 sparingly, with the culms and leaf-blades oi Phleum 

 praiense the common Timothy, and other grami- 

 naceous plants, in abundance, constitute its basis. 

 These are slightly interwoven; but the firmness 

 of the fabric is due in a great measure to the 

 previous condition of the materials utilized. 

 Moistened with water and plastered with mud, 

 they become firmly agglutinated so as to require 

 great effort to detach them from the fabric. 

 Sticks are but seldom used. The inside is lined 

 with the stems of fine grasses, having a weather- 

 beaten appearance. Its thickness which is nearly 

 I y^ inches, adds very materially to its firmness. 



Oviposition is closely attendant upon nidification, 

 and lasts nearly a week. In the performance of 

 the duties of incubation, the male takes no direct 

 share. Indirectly he aids in providing his partner • 

 with food, and in exercising a rigid surveillance 

 over the nest. The period of incubation ranges 

 from 13 to 14 days. It is worthy of remark in this 

 connection, that the time depends in an appreci- 

 able degree upon atmospheric mutations. 



