The Behavior of Xoddy and Sooty Terns. 231 



I attempted to get accurate tests of their time the birds became excited 

 and tried to go through the meshes as before. 



Experiment II. 



The following series of experiments was tried upon a marked male 

 sooty. .\ cubical wire box, 35 by 30 by 25 cm., was inverted over the nest. 

 .\ simple opening. 9 by 12 cm., gave access to the egg. This opening was 

 placed due west. 



The male on returning trotted round and round the box ; found tlie 

 door in 3 minutes ; was uneasy ; attempted to get out but could not find 

 opening. Stuck his beak in and out between the meshes. Became excited 

 and tore at the wire with beak for several minutes. A slight disturbance 

 in the neighborhood at which the other birds flew up caused him to re- 

 double his elTorts to escape. Got out at the end of 14 minutes. Walked 

 awav for a foot or two, trotted in again immediately. Was uneasy and 

 came out again, this time without useless movement. On trying to reenter 

 a moment later, he missed the opening and went halfway round the box and 

 returned before entering. Out again immediately. In returning again 

 missed his way in and went three- fourths around the bo.x, turned and en- 

 tered. This time he turned the egg with his beak, but would not sit down 

 upon it. Out again immediately. Entered after a few useless move- 

 ments. Tried to come out again immediately, became confused and fought 

 the wire. Stopped to adjust the egg, but again would not sit down. Came 

 out again immediately, then entered and sat upon the egg, this time in appar- 

 ent comfort. The box with its opening produced no further disturbance. 

 Time for adjustment to new situation under above conditions, 30 minutes. 



I left the box in position the rest of the day. On the following morn- 

 ing, since the marked bird was still on the nest, I carried this test further 

 by piling up loose sand around the entrance. The bird on returning was 

 not in the least frightened by the change. Went immediately to the door, 

 but finding the sand, walked round and round the cage trying to force his 

 way through the meshes of the wire. Tried to get into door again and 

 again, but would not scratch at the sand. Divided his time pretty well be- 

 tween the east side of the box. where the egg could easily be seen, and the 

 west side, where he had formerly gained admission. Bird was very persis- 

 tent, but at times would walk away for a few feet and then run hastily 

 back to the bo.x and continue his useless movements. I then scraped awav 

 the sand so as to expose an inch of the opening. The bird alighted and 

 passed by the door again and again. Apparently no perception of the situ- 

 ation as a whole. I then exposed two inches of the opening so that only 

 two inches of sand remained in front of the opening. Under these circum- 

 stances, the bird mounted the sand pile again and again and attempted 

 to peck his way through the meshes of the wire above the opening. Finally 

 bv accident he poked his head through the opening and squeezed through, 

 making no eft'ort to enlarge the opening. Time of whole experiment. I hour. 



After 5 minutes I drove the bird away (lifted up the wire box and 

 allowed him to flv) and piled the sand up to the height at which he had 

 previously been successful. Time for adjustment: 1.16 minutes. 



I next piled the sand up so as to completely cover the opening again. 

 After 20 minutes of random movement and no success, I scraped away the 

 sand so as to expose one inch of the opening. The bird came up and 



