206 SOME COMMON LAND-BIRDS. 



it would be hard to tell how she strikes so true a curve in set- 

 ting her first course of mud pellets. She may not always use 

 the same method, but I have seen her proceed as scientifically 

 as a mason. Coming with her load of mud, she clings to the 

 side of the barn with both feet and braces herself by her tail 

 at such an angle as to begin at one of the upper " corners " of 

 the nest. Then she deposits her mud in little dabs, not in 

 large lumps as she lays it on later in the work, turning on her 

 feet as a pivot and still keeping her tail fast applied to the 

 wall, although it is spread quite out of shape by the turning 

 of her body. She has struck out a circle, her feet the centre, 

 her bill making the circumference ; and by working in this 

 way, from the mud carried at that first load, she lays a line of 

 pellets nearly half around the circumference of the intended 

 nest. I do not know whether one bird is architect and master 

 mason, and the other merely a hod-carrier, but it is interest- 

 ing to see that they know the use of the compasses and that, 

 rather than lose their line, they prefer to hang in a cramped 

 position, sometimes almost head down. 



Rude as the work looks to us, these little masons are 

 skilful builders. They must also be trained architects or 

 their work would not stand the strain put upon it. What 

 do they allow for the weight of their families ? How do 

 they calculate the effect of the drought and sun on the 

 dry mud ? What are their tests for the adhesiveness of 

 their clay ? These are their masonic secrets, which they 

 never divulge. 



Wherever you find a large colony of eaves-swallows, you 

 will find conditions most favorable for mud-gathering. As 

 such choice places are not abundant, and as the birds are 

 social, large communities build together. Nearly always 

 their nests are on the south side of a barn, grouped under the 



