200 Papers from the Marine Biological Laboratory at Tortiigas. 



white shell and deposits it in the nest. This she repeats two or three times. 

 Both birds are active from now on until 5'' 05'", at which time the male 

 leaves for food. At y^ 05" he returns and feeds the female. 



The remarkable thing in all of these acts was the accuracy of orientation. 

 Many nests intervened between their own and the open spaces and many 

 other nests were in process of construction in the same bush. The nest was 

 localized with great exactness by each of the two birds at every trip. 



Finally, it may be said that the nest-building instinct is not so transitory 

 as certain others. All during my stay on the island the noddies were carry- 

 ing sticks ; even those caring for young do not resist the impulse to gather up 

 sticks. All my efforts to get control of their reactions by supplying them 

 with food and water were unavailing, but I could easily induce activity in 

 them by collecting a bundle of twigs and tossing them up in the air. Hardly 

 would the sticks fall before the noddies were after them. A noddy in mid- 

 air carrying a stick and dodging a dozen other birds in order to maintain 

 possession of the prize is one of the most common sights on the island. So 

 active and alert are they on the wing that if a stick is by chance dropped 

 while the bird is in tight, it is often caught before it strikes the earth or 

 the water. 



REACTIONS OF THE SOOTIES OBSERVED IN NEST-BUILDING. 



The building of the sooty nest is quickly accomplished. The obtaining 

 of a nest-site is the difficult part of the reaction. As has been said, the 

 sooties build their nests very near one another. For this reason it is ex- 

 tremely difficult to make complete observations. My observations began late 

 one afternoon, before any eggs had been laid. Hundreds of the birds were 

 grouped together, incessantly fighting and screaming. It quickly became 

 apparent that most of them had chosen a nest-site and were defending it 

 against all late-comers. Both male and female were present. Each pair in 

 this particular locality defended a circular territory, roughly 14 inches to 2 

 feet in diameter. Other birds in wandering around would stumble into this 

 sacred territory and a fight would ensue. The fights would often lead to 

 encroachments upon the territory of still other birds. The number of those 

 fighting would thus be constantly increased. I have seen as many as 14 

 sooties thus engaging in a fight. Birds 10 and 15 feet away would rush 

 into the fight and the noise and confusion beggared description. Some- 

 times as many as 10 or 15 such fighting groups could be observed in the 

 area of 1,000 square feet. Quiet would momentarily ensue and then be 

 broken by another series of fights. During the choice of the nesting-site 

 the fights continue day and night, with only intermittent periods of quiet. 



Within this charmed circle the two mated birds remain relatively quiet. 

 At this time sexual activity is at its height. It frequently happened in the 

 sexual process that the two birds would step outside of their own territory 



