40 HOMING AND RELATED ACTIVITIES OF BIRDS. 



disturb them. The birds behaved as in the previous test. After a time they ceased to make 

 attempts to escape and settled down in the water. In about 2 hours one sooty could no 

 longer rise from the water, and in 4 hours the second sooty became entirely water- logged. 

 At 6 o'clock, seeing that the sooties would soon be entirely helpless, I rescued them. At 

 my approach the noddies flew up and hovered in the air as if they had not been through any 

 difficult experiences, and when I opened the door they swam out and flew away. The sooties 

 were quite helpless. I took them in and kept them over night in a warm place. On the 

 following morning they were apparently as fresh as ever. 



These tests seem to show that the noddy is as at home in the water as in the air. It is 

 quite clear that it could stay on the open water in calm weather indefinitely, and that even 

 in rough weather it could probably last out by alternately alighting on the water and then 

 flying up. It would seem from the above tests that the sooty would be unable to last over 

 night in the water unless some aid were at han-d. Incidental observation leads me to sup- 

 pose that the sooty is the better flier. As was brought out in an earlier paper, the sooty 

 joins the man-o'-war birds and the pelicans in difficult flying feats. These birds gathered in 

 crowds and circled around and around, going up completely out of sight. Again at night the 

 sooty is far more on the wing than the noddy. Furthermore, the sooty flies higher, much 

 higher, than the noddy. In coming in at night from the water the noddy nearly always 

 takes the lower strata, flying usually not more than a few meters above the surface. The 

 sooty, on the other hand, flies high. Occasionally one sees two sooties darting off together 

 and keeping parallel courses, no matter how the direction of the flight may be varied. Both 

 wheel to the right or to the left, down or up, in a way quite similar to the evolutions of the 

 pigeon. One never sees noddies engaged in this form of play. It would seem that the two 

 species differ markedly in their behavior towards the two elements, air and water. 



6. I became anxious to find out if the fate of the sooty forced to spend the night upon the 

 water were changed if small pieces of drift-wood were at hand. Two noddies and two sooties 

 were put into the cage as before. This time I had tethered against the tide 4" by 6" 

 by 6" pieces so that they floated free and were held away from each other. The sooties 

 alighted first on the water. The two noddies began alighting on the blocks almost immedi- 

 ately (plate 5, figs. 2 and 3). As I write, 10 minutes later, both sooties are in the water 

 and both noddies on the blocks. The blocks keep turning over in the water, since the 

 tide is running out rapidly and it is hard for the birds to keep their footing. The sooties 

 make little or no effort to take the other two blocks. They sometimes fly up in the air, 

 but rarely attempt to take the blocks. One just caught the block (plate 5, fig. 2), but 

 flew up immediately and did not again attempt to alight on it. The noddy when alight- 

 ing goes always to the block. At the end of the first ten minutes one sooty began con- 

 stantly to climb up and ride on the block but could not stay on very well. The other sooty 

 had not made the slightest attempt to alight on it. The noddies at the end of twenty 

 minutes never alighted on the water. At the end of 25 minutes one sooty, which had been 

 constantly in the water, was no longer able to rise from it (plate 5, fig. 4). Two hours 

 later the bird which was unable to rise escaped by reason of the fact that the tide had 

 dropped below the top of the door in the side of the cage, which I had neglected to close. 

 The other three birds each possessed a block and were calmly standing upon it, making no 

 efforts or struggles to escape. At l h 15 m the sooty had perfectly mastered the block and 

 seemed quite content. It apparently had to learn to use the block and did not go 

 instinctively to it. At 2 p. m. I captured another sooty and placed it in the cage. The 

 behavior of this bird was wholly similar to the above. Its efforts disturbed the other sooty, 

 which began to make struggles to escape, becoming uncoordinated in its movements, and 

 finally dropping into the water. At 4 h 30 m both sooties were in such poor condition that I 

 decided to release them. The noddies were still in as good condition as before. 



7. On June 9, I tethered heavy pine boards 1" by 6" by 8" as floats. They were fastened 

 at both ends, so that no matter which way the tide was running they would remain relatively 

 stable. Under these conditions the sooties passed the night comfortably and were in perfect 

 condition on the following morning. 



It seems quite clear from these experiments that if the sooty could find fairly 

 heavy pieces of drift-wood in the Gulf or beds of sea-weed, which are probably 

 always present, it would be able to pass an indefinite period of time upon the 

 water. Up to the 1913 experiments I had supposed that this inability to pass 



