NESTS OF MUD. 43 



nests which are constructed out of moistened 

 earth, and the fabrication of which singularly illus- 

 trates the ingenuity and skill of the little archi- 

 tect. The swallow is our most familiar example 

 of a mud-building bird. As soon as the situation 

 has been decided on, the birds proceed to collect 

 the materials. In the performance of this duty 

 they may be seen often at the edges of ponds, 

 busy in gathering up small portions of moist 

 earth. Sometimes they may be seen by the mar- 

 gins of puddles, in the road-side, collecting these 

 pellets of earth. They then fly away with them 

 to their selected site, and here proceed to fasten 

 them against the wall. These pellets are bound 

 together (on the same principle as bricklayers 

 employ hair mixed in their mortar) with straws 

 and bents ; and the structure is then moulded into 

 a saucer-shaped nest, the interior of which is lined 

 with feathers. The house-martin employs similar 

 materials, and, like the swallow, may often be seen 

 on the ground, in damp places, collecting the mud. 

 " It seems probable," observes Mr. Yarrell, " that 

 the earth is mixed with the saliva of the bird, by 

 which its tenacity is increased." White remarks, 

 " A martin built its nest against the glass of a 



