NESTING ACTIVITIES OF NODDY AND SOOTY TERNS. 



71 



neighboring nest was visible. The sight of this nest seemed in every case to furnish the 

 basis for orientation, for the bird always hastened back to her own nest after looking at the 

 neighboring one. After 15 minutes she found the egg in its new position and soon covered 

 it, to all appearances satisfied ; 5 minutes later she was driven away, returned to the southern 

 end of the brush pile, and walked to the old nest site by the customary path. She settled 

 down in this position for a few minutes, then became dissatisfied, went over to the egg, 

 adjusted it, and covered it. 



The path from x to 2 was then blocked by piling brush at y. The bird alighted near the 

 nest at x, started along the path, came to the pile of brush, and seemed to be completely 

 lost. She wandered about for a long time and finally came to the nest (o) at the other end 

 of the brush pile. She crawled into the brush and inspected this nest, then turned and 

 scurried around to her own nest at z as fast as she could run. The nest at o, like that at x, 

 served as a landmark. 



Under normal conditions a nest near the alighting place furnished the bird a 

 clue to the direction of its own nest and the path to the latter was followed 

 almost wholly by a series of kinsesthetic-motor habits. The bird was able to 

 re-orient from other visual stimuli when the usual method was prevented. 



EXPERIMENT 9. 



An isolated nest upon the beach, just at the foot of a steep sand bank covered with dead 

 bay-cedar bushes, was chosen for observation. The environment of the nest is shown 

 roughly in figure 6. The nest was at the position marked d. The brooding bird was driven 

 off several times and her return noted. She never alighted upon the beach, but always 

 upon the top of the bank, among other nests, at a distance of more than 8 feet from her 

 own (at a or 6). From this point she walked to her nest, following a winding path about 

 12 feet in length. This path led through a clump of weeds, straight down the face of the 

 bank, around a dead bay-cedar bush, and along the foot of the bank for 4 feet to the nest. 

 Along the path were five other nests, which were always avoided carefully. These nests 

 were on the face of the bank; there were no other nests at its foot. 



FIG. 6. Nest at the foot of a sand bank, with the path from 

 the alighting place shown by the dotted line. 



Moving the nest along the foot of the bank for a distance of 2 feet in either direction did 

 not seem to affect the bird's behavior in the least. A piece of canvas was placed against 

 the face of the bank so as to cover the bird's path from the top to the foot. The canvas 

 was nowhere nearer than 5 feet to the nest and did not cover the bird's alighting place at 

 the top of the bank. The bird returned, seemed frightened, but in 5 minutes alighted and 

 walked upon the canvas. She started down the bank in the right direction, but became 

 confused as soon as she got upon the canvas, and returned to her usual alighting place. 

 She made several more false starts, became accustomed to the canvas, and walked upon it 

 without hesitation, but never walked the full distance to the foot of the bank. She went a 

 short distance to one side of the canvas and reached one of the nests bordering her path (c). 

 She looked at this for a moment, and then turned and ran rapidly in the direction of her 



