NESTS AND NEST-BUILDING IN BIRDS 



345 



TABLE VI 



Activity Record of Building Robin, Illustrating Molding, Turning and 



Alteration 



No. of 



molds 



at each 



visit 



23 

 41 

 27 

 27 

 38 

 53 

 52 

 56 

 48 



Direc- 

 tion of 

 turniiiii 



L 

 R 

 L 

 R 

 L 

 R 

 L 

 R 

 L 

 R 



No. of 

 revolu- 

 tions de- 

 scribed 



2 — 



3 + 

 2 

 2 

 3 



3i 



4 



3 



Time 



away 

 from 

 nest 



1+ 



12 

 5+ 

 7' 

 6+ 

 6 



24 



10+ 

 3 



14 



showed only wet mud on the inside of the cup, the wahs of which 

 had risen to a height of nearly two inches. It is thus evident 

 that the materials are not treated indifferently, but that at a 

 certain stage the plastic mud is centrally placed, and the pres- 

 sure so applied that it is pressed outward and downw^ard into 

 the interstices, thus engulfing weeds and stubble, and thus 

 producing the mortar referred to above. This mortar is thus 

 an incidental product of the molding process, for whatever 

 the disposition of the soft mud its mixture with the other mate- 

 rials would be inevitable. The form and symmetry of the cup 

 however, is dependent not only upon the molding and turning, 

 but upon an effective distribution of the materials by the bill. 

 If such a nest w^ere incinerated, the clay cup only would remain, 

 smooth and regular within, but outwardly drawn into irregular 

 processes representing the interstices of the parts removed. 



Not a spear of grass was to be seen on the inner wall of the 

 cup at this period, nor was I able to tell from the appearance 

 or feeling of the wet clay whether this bird had last turned to 

 right or left. There is no twist of the body in molding, and the 

 smoothing which is effected, as already noted, is due to succes- 

 sive "stampings" of the breast upon yielding materials. It 

 is not therefore probable that the bird receives any clue to turn- 

 ing direction through the tactile sense. The tendency to alter- 



