OF EASTERN PENNSYLVANIA. 17 



that the typical nest is constituted of a basis of 

 leaves, chiefly of Quercus and Fagus, loosely ar- 

 ranged in the bottom, and gradually increasing in 

 compactness from below upward; strengthened 

 and secured in a partially hemispherical attitude 

 by the aid of small twigs. This is surmounted by 

 a superstructure which consists of a heterogeneous 

 mass of plant-stems in an advanced state of 

 decomposition, decayed fragments of wood re- 

 sembling pine, a modicum of mud closely impacted, 

 instead of decayed deciduous leaves according 

 to the authority of the above eminent ornitholo- 

 gist; over all is a layer of roots intricately ar- 

 ranged. No further amendment seems necessary. 

 The environment of this Thrush like that of the 

 Robin, occasionallv determines a marked deviation 



J 



from the normal structure. In a nest which we 

 have before us, which was built upon the horizon- 

 tal branch of a species of Finns, along a carnage 

 drive which was daily the scene of much bustle 



j 



and clatter, there is lacking the internal parch- 

 ment-like layers. Externally there is a layer of 

 the dried leaves of Oucrcus and Fa pus, the inner 



' O 



bark of trees, and largely of the blades of grasses 

 possibly of Dactylus glomerata or Orchard-grass ; 

 occasionally, scraps of paper form a noticeable 

 feature. Interiorly there is a thick lining of small 

 roots and grasses. Five or six days of steady 

 application by both sexes, are ample for the con- 

 struction of a nest. 



The period of incubation commences not earlier 



