The Behavior of Noddy and Sooty Terns. 225 



Experiment I. 



(a) An isolated nest under a bush was chosen for purposes of experiment- 

 ation. Nest was left intact, but the egg was removed and placed in a new 

 nest dug 18 cm. due north. Bird returned to the old nest and stood im- 

 passive. Attempted to settle down on the nest and to poke egg, then 

 looked up and saw egg, crawled over to it and sat down upon it. Bird got 

 up and adjusted the egg and nest elaborately. Time for adjustment to situ- 

 ation, 30 minutes. 



{b) I then allowed the bird 30 minutes at the new nest. At the end of 

 this time I scared it away and placed its egg back in the old position, put- 

 tmg another sooty egg in the nest I had made. Result : Bird went back to 

 old nest and covered egg without so much as looking in the direction of the 

 new nest. 



(c) Experiment (a) was repeated with similar results. 



{d) Twenty minutes allowed for repose after above experiment. New 

 nest No. 2 was then made 18 cm. due west of new nest No. i. Result: Bird 

 went back to original nest, shaped the nest, and scratched around in it and then 

 walked over to new nest Xo. 2 and sat down on egg after adjusting it. 



{e) Twenty minutes again allowed bird in this position. I then fright- 

 ened it away and noted the pathway of return. The bird walked by old 

 nest, inclined toward it slightly, then walked on directly to the egg in new 

 nest No. 2. 



Experiment II. 



A nest in the sand in an open space was chosen. A large tuft of grass 

 was situated near. This made a very prominent visual characteristic. I 

 pulled up the tuft of grass, obliterated the old nest (marking it with a 

 pebble), making a new nest 88 cm. due north of the old, inserting the tuft 

 of grass as nearly as I could in the same relations to the new nest as it 

 stood to the old. Bird on returning stood for S minutes at old nest, then put 

 down beak and attempted to arrange the egg just as though it ivere present. 

 Later, bird walked over to the new nest, partially sat down, then got up 

 and went back to the old nest, turned round and round in the exact position 

 of the old nest, walked over to the new nest, arranged the egg, went back to 

 the old nest, remained there at a loss for several minutes, turning head 

 round and settling down with body exactly as though egg were present, then 

 went over to the new nest and sat on the tgg for a moment or two, then 

 back again to the old nest. Finally adjusted the new nest elaborately and 

 remained there in peace. I then frightened it away. On returning, it re- 

 peated the above reactions, but with fewer trial movements. A second time 

 I scared it away ; again it returned to old nest and tried to get contact with 

 egg. This second time it stood at the old nest for a long time, fighting all 

 the other birds away. Finally, at the end of 10 minutes again walked over 

 to the new nest and sat down. I scared it away again after allowing it to 

 sit on the new nest for 12 minutes. Bird gone for 30 seconds. On return- 

 ing, alighted from the air exactly upon the center of the old nest and again 

 tried to adjust to nest in the old way. At end of i minute and 35 seconds 

 waddled over and sat down on egg in new position. Was driven away again 

 after 10 minutes of repose. Again alighted upon old position. Repeated 

 it again ; again alighted on old nest, but this time left it for the new in 12 

 seconds. Again alighted near old nest, ran to it and stopped there for an 

 instant, passing rapidly on to new nest. Again alighted on old nest, but 



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