NESTS AND NEST-BUILDING IN BIRDS 339 



her breast against the insignificant and incoherent mass of 

 materials gathered, applying the pressure mainly by scratching 

 movements of the feet, with wings half spread and vibrating, 

 the tail pumping and usually depressed, while the whole body 

 shook from the violence of the effort exerted. Such a complex 

 series of movements involving the entire body so far as the 

 skeletal miuscles were concerned, we shall call a Molding Move- 

 ment or simply a " mold." It is a " stamping " movement 

 with the use of the breast as form, and commonly lasts from 

 five to ten seconds, according to circumstances. The bird 

 then rises, turns through an arc of six or seven degrees to the 

 right or left; this we shall call the Turning Movement. She 

 then settles as before and applies the next mold, and these 

 acts may be repeated for the twentieth or fiftieth time, when 

 from two to four complete revolutions are described by the body 

 of the turning bird. These turning movements are all commonly 

 in the same direction, that is if the robin makes the first turn 

 to the right, this direction is continued to the end. Exceptions 

 to this rule will be given later. 



When this robin came with a second load precisely the same 

 motions and behavior were repeated with one exception ; if at 

 the first visit she turned to the right, at the next she swerved 

 to the left. In this case there was perfect alternation of turning 

 movements, whatever the interval spent either at the nest or 

 away from it This remarkable fact will be discussed a little 

 later. 



Aside from the molding, turning and alternation observed, 

 another and very different characteristic of the building robin 

 is to be noted; I refer to the Arrangement of Materials with 

 the bill. After depositing upon the site what has been brought, 

 the bird disposes of the material in a rather definite way, or 

 at least in a manner to produce definite results. Not only 

 are the straws, weeds and the like drawn from without inwards 

 to prevent loss, but later, as we shall see, there must be a definite 

 disposition of the mud and stubble in order that a cup can be 

 modelled and a serviceable mortar produced. 



To revert to the molding process ; the scratching movements 

 of the legs are often very violent from the first, and the sound 

 of the claws on the bark of the limb can be distinctly heard 

 at a distance of several yards, even after the work of building 



