The Behavior of Noddy and Sooty Terns. 235 



noddies were allowed to accustom themselves to entering and leaving the 

 nest by way of the opening. When they had become thoroughly accus- 

 tomed to the box it was possible to interpose obstacles in the way of their 

 adjustments to the nest, by putting certain simple obstructions at the open- 

 ing. Only enough tests were made to prove the applicability of this method 

 for controlling the reactions of the noddies. The following extracts from 

 my notes show the behavior of the birds in adjusting to the box when no 

 obstructions were interposed at the door : 



Both birds present (one marked). They alighted on top of the box 

 and attempted to poke heads through the meshes of the wire. After 15 

 minutes of random effort, the marked bird found the entrance and imme- 

 diately covered the egg. I scared this bird out and before it returned the 

 unmarked bird found the entrance and covered the egg. Both birds adapted 

 themselves to the situation very quickly. 



After allowing the birds several days in which to get entirely accustomed 

 to the box, a white bristol board sector was inclined at an angle to the cage 

 entirely covering the entrance when approached from the front. The end of 

 the cardboard, which rested on the ground, was pointed so that when the 

 cardboard was struck or pushed it would fall over, thus exposing the en- 

 trance. 



First trial: Bird alighted on a limb very near to the entrance and stood 

 for a moment, then flew away. Returned and alighted as before, opened 

 its mouth and gazed at the egg in a stupid, inert way. After standing for 

 some time the bird again flew away and again returned. This was repeated 

 four times. It then began flying away and returning to the top of the cage. 

 This behavior of flying out over the water and returning to some new 

 position on the cage was repeated many, many times. At last it alighted 

 on the perch and stuck its beak in at the crack made by the cardboard's 

 being inclined at an angle to the opening. By degrees the cardboard was 

 pushed aside and the bird entered. Time: 41 minutes. 



Second trial: (10 minutes later). Flew against the cardboard, attempt- 

 ing to insert beak at the same time. Repeated several times. This was a 

 clumsy but ingenious method. Time: 15 minutes. 



Third trial: (One day later). Alighted on top of the box, flew away, re- 

 turned, then flew at the door as in the last test, pecked in a slow and foolish 

 fashion, finally pecked it open. Time : i hour. 



Fourth trial: (10 minutes later). Many trial movements as in the above 

 case. Time: i hour and 15 minutes. 



Fifth trial: (One day later). (Egg had hatched during night.) Bird 

 flew at door, mate sat stupidly on top of box. Flew against the door again, 

 finally opened it by this means. Time: 13 minutes. 



Sixth trial: (10 minutes later). Many useless movements as before. 

 The bird still attempted to remove the obstruction by flying against it. If 

 this failed it fought at the wires on top of the cage. Mate stood stupidly 

 on top of the box the whole time, but made no effort to imitate, follow or 

 assist the marked bird. The cardboard was finally knocked down with the 

 wings. Time: 16 minutes. 



Seventh trial: (One day later). After flying against it several times the 

 cardboard fell. Time : 6 minutes. 



