DWELLINGS 1637 



the air; this is the nest. The female broods by 

 sitting with her legs hanging over the sides of the 

 hillock on which her little family prospers above the 

 waters and the damp soil. 



A perch in the Danube makes a dwelling of dried 

 earth in the form of an elliptic cupola, and prepares 

 a semicircular opening for entry and exit. 



The bird which shows itself the most skilful mason 

 is probably the oven-bird (Furnarius rufus) of 

 Brazil and La Plata. Its name is owing to the form 

 of the nest which it constructs for brooding, and 

 which has the appearance of an oven. It is very skil- 

 ful and knows how to build a dome of clay without 

 scaffolding, which is not altogether easy. Having 

 chosen for the site of its labors a large horizontal 

 branch, it brings to it a number of little clay balls 

 more or less combined with vegetable debris, works 

 them all together, and makes a very uniform floor, 

 which is to serve as a platform for the rest of the 

 work. When this is done, and while the foundation 

 is drying, the bird arranges on it a circular border 

 of mortar slightly inclined outward. This becomes 

 hard ; it raises it by a new application, this time in- 

 clined inward. All the other layers which will be 

 placed above this will also be inclined toward the in- 

 terior of the chamber. As the structure rises, the 

 circle which terminates it above becomes more and 

 more narrow. Soon it is quite small, and the animal, 

 closing it with a little ball of clay, finds itself in 

 possession of a well-made dome. Naturally it pre- 

 pares an entrance; the form of this is semicircular. 

 But this is not all. In the interior it arranges two 



