NOTES ON THE NESTING ACTIVITIES OF THE NODDY 



AND SOOTY TERNS. 



BY K. S. LASHLEY. 



ORIENTATION IN THE NEST LOCALITY. 



In the report of his extensive studies of the activities of the noddy and 

 sooty terns* Watson raises the question of the method by which the birds 

 recognize their nests and young and records the results of a few experiments 

 bearing upon the problem. The terns breed in great numbers upon Bird Key, 

 an island in the Tortugas group somewhat less than 5 acres in area. Their 

 nests, of which there were more than 10,000 in 1908, are in may cases closely 

 crowded together, as many as 30 sooty nests being found in an area of 100 

 square feet, and the nests and eggs are almost indistinguishable to the human 

 observer. Indeed, the island suggests a city of 10,000 houses, all much alike, 

 unnumbered and set down at random, without streets or definite landmarks. 

 The birds choose their own nests, without error, from among hundreds of 

 similar ones, and under normal conditions never show the slightest hesitation 

 in making their choice. 



In testing the sensory factors involved in nest recognition, Watson found 

 that he might change the appearance of the nest and egg without disturbing 

 the birds in the least. Very great changes in the appearance of objects near 

 the nest did not alter the quickness and accuracy of orientation. When, how- 

 ever, the slightest alteration was made in the horizontal position of the nest, 

 when it was moved only a few inches to one side, the birds were much confused, 

 refused to occupy the nest in its new position, and reacted positively to the 

 original nest site even when no trace of the original nest remained. Many 

 observations of such behavior led Watson to conclude : 



In the case of both the noddj* and the sooty, the nest locality is the important factor, the 

 nest itself being reacted to by virtue of its location within this locality. Since environment 

 can be greatly changed without altering the bird's accurate adjustment to the nest, it is 

 evident that if the adjustment is made in terms of visual data, the visual envhonment which 

 serves as the stimulus must be complex and have a wide extension. I am not prepared to 

 admit, from the above experiments, that adjustment takes place in terms of vision alone. 



In view of the remarkable ability of the terns to return to their nests from 

 great distances the problem of the sensory factors involved in their recognition 

 of the nest locality and orientation in the neighborhood of Bird Key becomes 

 of considerable importance as offering a possible aid to the understanding of 

 more distant orientation. 



At the suggestion of Professor Watson I attempted to gain further evidence 

 upon the problem of proximate orientation in the terns during a six weeks' 

 residence on Bird Key. The work has not furnished any clue to the mechan- 

 ism of distant orientation, but the details of the birds' behavior in finding and 



*.Johu B. Watson. The Behavior of the Noddy and Sooty Terns. Papers from the Tortugas 

 Laboratory of the Carnegie Institution of Washington, Publication 103, 1908. In this is 

 included a general description of the activities of the terns during the nesting season. The 

 reader is referred to the paper for figures of the birds at different ages and for a more complete 

 description of the behavior of the birds at different times during the nesting season than is 

 given here. 



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