& 



Tlic Bcliavior of X'oddy and Sooty Terns. 211 



case it stands about 2 feet from the nest, fightino- all birds which approach.. 

 Once when this G drove a strange bird too near S, S left the egg to assist 

 in the fight. Often in sitting down on the egg 6" rocks it gently, turns it 

 with the beak, and gradually brings her weight upon it.^ 



Birds on alighting, if orientation has not been exact, have to run the 

 gauntlet of hundreds of sharp beaks before they finally reach their own 

 nests. Since this is constantly occurring, it greatly adds to the general 

 confusion. Where the nests are under the bay-cedar bushes the birds on re- 

 turning usually alight near the edge of open spaces and then run on foot 

 to their nests, whire if the nests are in the open spaces they circle around 

 until the nest is located, and then alight. 



During this observation I saw three cases of feeding at nest-site where 

 no egg had been laid. Feeding was accomplished with great difficulty. 

 Dozens of other birds attempted to interfere, especially the G's of nearby 

 nests. - 



One case of shift at the nest was observed. .S" had been on the nest dur- 

 ing the whole previous time of observation. Suddenly G went to the nest 

 an"d gradually pushed 5' aside. G sat on egg for a few moments, then got 

 up. S sat down on egg immediately. G then returned, pushed 5 aside, 

 adjusted carefully, and remained on the egg. 



During this observation and in many others my attention was called to 

 a peculiar reaction in the male. When approaching his mate and at times 

 other females, he would arch his neck, droop his wings, lower his head 

 slightly, turn the head to one side, and strut around and around the female, 

 at times raising his head and then lowering it. The reaction is very similar 

 to the one exhibited by the cock of our common barnyard fowls when he 

 has called the females to feed. Figure 19, plate 7, shows 2 males in this 

 attitude. 



My notes show that in some cases during the brooding period the birds 

 sit quietly on the egg the whole day long, even in the midst of the turmoil 

 which is ever present. 



In summarizing this unsatisfactory section we may say : 



(i) The presence of the egg brings about a change in the disposition of 

 the sooty which is ven,' similar to the one already noted in the noddy. 



(2) One important difference between the two species of birds is to be 

 noticed whereas the shift at the nest in the case of the noddy occurs once 

 in 2 hours, the shift in the case of the sooty occurs once in 24 hours. This 

 leads us to conclude that there must be an enormous difference in the 

 wav in which organic data function in controlling the reactions of the 

 two species. 



The general impression one gets from close observation of the sooty is 

 that auditory and visual stimuli play a more important role in its life than 

 in the life of the noddy. 



' See fig. 2, plate i. 



'This same reaction was often noticed when the parents attempted to feed the 

 young. 



