HISTORICAL AND EXPERIMENTAL STUDY OF HOMING. 



45 



Data supplementing the above may be obtained by referring to table 4, 

 p. 42, which gives a record of 13 birds returning from the Galveston trip 

 (places are marked by the words "mate returned"). The length of time the 

 birds were out is given in table 7. 



TABLE 7. 



Sooty No. 1 returned after 14 days. 

 5 returned after 19 



8 returned after 14 



9 returned after 11 



10 returned after 14 



11 returned after 14 



12 returned after 14 



Noddy No. 14 returned after 22 days. 



17 returned after 22 



18 returned after 14 

 20 returned after 11 

 22 returned after 11 

 24 returned after 14 



In this test, where the birds were not held in captivity, we find 7 sooties 

 returning to the nest after intervals varying from 11 to 19 days and 6 noddies 

 after intervals varying from 1 1 to 22 days. In most cases where the nest had 

 been maintained by Os, the Rs on returning resumed normal nesting activities 

 with their former mates. We thus see that under these more natural conditions 

 the nesting impulse remains strong from 2 to 3 weeks and that the habits of 

 reacting to a particular nest and nest mate are also retained during this period. 



The question arises, of course, as to how many birds returned to Bird Key 

 after the various expeditions but escaped observation through the waning of 

 the nesting instincts or the loss of nest habits. This question is not wholly 

 answered by our experiment. It seems improbable that birds returning under 

 2 weeks could have escaped observation. If return was delayed much longer 

 than this (as was perhaps the case in many instances) it is probable that the 

 presence of the birds at the nest was too sporadic to be detected by non-con- 

 tinuous observation. 



GENERAL TECHNIQUE OF THE HOMING EXPERIMENTS. 



The following routine was adopted on Bird Key in preparing for an experi- 

 ment on homing. Roads were first cut through the thickly populated noddy 

 and sooty districts. These roads may be cut at any time before May 15 (they 

 should not be cut later than this because of the number of eggs which are on the 

 ground). It is easy to capture both noddies and sooties on these roads, and 

 easy to observe their return. Where, in the course of a season, so many birds 

 are likely to be on the road, it makes it very much easier to take all of the 

 Galveston birds, e. g., from one road, the Key West birds from another, etc. 

 As one passes down the roads the boldest of the birds will stay on the nests, 

 or if they do leave momentarily, they will fly back while the experimenter is 

 standing close to the nest. These bold birds are the ones always captured. 

 Before passing down the road for the purpose of capture, stakes about 12 

 inches long and 1 inch square are made. A large Dennison tag and a small tag 

 are attached to the end of the stake, the small tag being attached loosely. 

 The two tags bear identical legends. The large tag will have written upon it in 

 water-proof ink, e. g., "Sooty, Galveston, removed May 16, marked with 

 scarlet lake, 3 bars on head and neck." When the bird is captured the stake 

 is pushed down into the sand if a sooty or tied to a convenient twig if a noddy 

 very near to the nest (plate 6, figs. 1 and 2). The small tag, bearing a 

 duplicate of the above legend, is pulled off. The bird and small tag are handed 

 to an assistant, who ties the tag around the bird's neck and puts the animal in 



