3 20 Papers from the Marine Biological Laboratory at Tortugas. 



have been used as a stimulus for controlling their reactions. In future work 

 it would be worth while to give this method a thorough test and to compare 

 it with the method described below. 



A Httle experimentation soon convinced me that the method of using the 

 nest locality in place of food was desirable under the circumstances, since 

 the stimulus of the nest locality is almost as potent in its effects upon the 

 reactions of these birds as the stimulus of food on the reactions of other 

 animals. While this method of forcing the bird to overcome difficulties in 

 order to reach the nest may not be so accurate nor so uniform in its stimu- 

 lating effect as is the case when food is similarly used as a stimulus, it 

 certainly has present in it all the elements of naturalness which even a 

 Wesley Mills could demand. Before giving the results obtained from the 

 use of this method, certain experiments bearing upon the general problem 

 of recognition will be discussed. 



TESTS WITH NODDIES AS TO RECOGNITION BETWEEN MATES. 



My observations at the nests show that there is present in the noddy a 

 very accurate functional recognition of both nest and mate. It will be re- 

 membered that, to our eyes at least, the male and female noddy are indis- 

 tinguishable. The question then becomes a pertinent one as regards the 

 way in which the female recognizes the male and z'icc versa. Is there recog- 

 nition between the two birds or is the nest alone recognized and reacted to? 

 From much observation, unsupported however by experimental work, it was 

 forced upon me that the male and female could recognize each other, at 

 least within the nest locality (actualh' observed recognition of this func- 

 tional kind took place within a radius of lo to 12 feet). 



A few preliminary unsatisfactory tests of the following kind were made 

 upon this subject: Two birds were caught from marked nests and treated 

 in the following way : The black neck feathers of noddy No. i were dyed 

 red with Higgins' ink. The white head and eye-spaces of noddy No. 2 

 were dyed red in a similar manner. 



Noddy No. i. Released at 4'' 28'" p. m., 30 feet from nest. Flew to 

 water at once and " dived " six times into the water. Circled back to nest, 

 alighted, and covered egg at once (mate being absent). A few moments 

 later the mate returned, would not alight, circled around the nest several 

 times, then sat down near the nest for a long time ; then hopped upon the 

 nest and pecked at the marked bird. Sat behind the marked bird for a long 

 time, then both birds began nodding to each other in a very ludicrous 

 fashion. After 40 minutes the unmarked bird crawled upon the egg, the 

 marked bird taking up a position on the rim and nodding to the unmarked 

 bird. One minute later it again flew to the water and began diving. Two 

 minutes later it returned and alighted near the nest. No further family 

 dissension seemed to be caused by the dye. 



Noddy No. 2. The behavior here was in marked contrast to the above. 

 No. 2 was likewise released 30 feet from the nest. Flew immediately to 



