OUR FEATHERED ENGINEERS. 71 



lecture into classes which will include all the most 

 characteristic methods of building. 



i. Plasterers. In our first division, we will 

 briefly glance at a few of the birds which are in 

 the habit of mixing a portion of the nest materials 

 into a rude kind of paste or plaster. One of the 

 best examples of this peculiar class of architecture 

 is the nest of the common Song Thrush, a bird as 

 well known as it is appreciated for its sprightly 

 form and charming song. The Song Thrush's 

 nest undergoes two very distinct stages in the 

 course of its construction. In the first place, the 

 outside nest is formed of dry grass, scraps of 

 moss, and sometimes a few slender twigs. This 

 rather loose and flimsy nest is then carefully and 

 compactly plastered with a thick coat of wet mud, 

 worked well into the grass, and then the whole 

 structure is finally lined with a thinner coating of 

 rotten wood. This latter material is obtained 

 from logs of wood or decayed stumps, those satu- 

 rated with moisture being preferred. If none wet 

 enough can be found, the birds moisten it in the 

 nearest water, and with feet and bill work it on to 

 the lining of mud, using their breast to finally 

 smooth and round their beautiful handiwork. The 

 whole structure is then generally left a day or so 

 to partly dry, ere the first egg is deposited. The 

 heat from the sitting bird soon completes the 

 plastering process. We cannot help admiring the 

 wonderful instinct which prompts the bird to 

 select such a material for the final lining of its 



