HISTORICAL AND EXPERIMENTAL STUDY OF HOMING. 41 



the night upon the water in the absence of drift-wood accounted for the 

 failure of many of the birds to return to Bird Key. The 1913 ex-periments 

 upon homing between Galveston and Bird Key (p. 54) seem to show that 

 entire reliance can not be placed upon the results of the e.xperiments we have 

 just considered. In the Galveston tests many of the birds were out upon the 

 water (apparently) during periods ranging from 5 nights to 17 nights Hence 

 we must conclude either that drift-wood was abundant or else that the sooty 

 when not confined can spend the night upon the water. If our results are 

 taken at their face value they would seem to force the conclusion that the 

 Galveston sooties were able to find something to rest upon during the night. 



RETENTION OF NESTING HABITS. 



In controlling experiments upon homing it becomes essential to know (1) 



the length of tune the bird left on the nest (0) wOl care for the nest, egg, young 



etc., and (2) the length of time nest habits will be retained bv the bird which 



has been sent away (R). The necessity for data on (1) arises by reason of 



the fact that as soon as the bird left at home begins to desert the nest other 



bu-ds steal the straws, if it is a noddy nest, or fill it with sand, disarrange the 



egg, etc., if It IS a sooty nest. Nests so disturbed will not be taken by bii-ds 



retunung from the experiments on homing. Since the observer can not keep 



all 01 the nests under observation at any one time, it is essential that they be 



kept m good condition by the bird remaining at the nest. In order to control 



this factor perfectly it would be advisable in future exTerimentation to invert 



wire cages (with open doors) over the nests several days before capturing the 



bu-ds which are to be .sent from the island. These nests could be watchecl and 



as soon as the at any given nest begins to desert, the door of the cage could 



be closed up until R was expected. R having been habituated to the cage before 



he left, would not hesitate to enter it on his return if the door were left 



open or to perch upon it if the door were closed 



The necessity for data on (2) appears when we consider the possibility of the 



oflnL*^ T. K^T^m""'" ^"' ^^'^"^^ "^ ""''^ ^''^'^^'' "P«n the possibilitv 

 of loca mg the bird (R) upon its return. If nest habits, habits fonned to a 

 particular nest, to mate, etc., are lost at the end of 2 or even 3 weeks it is 

 unlikely that the total number of birds returning from long trips can ever be 

 observed. Fairly complete data have been gathered upon (1) 



OBSERVATION UPON BEHAVIOR OF BIRD LEFT AT NEST (o) AFTER REMOVAL OF 



NEST MATE (r). 



onfv Tl"!^' ,f ^'"'^f °"^, *^^^^ been made upon this phase of the subject, that 

 only a small number of our records ^vall be given. We present in table 4 

 the behavior of 24 birds whose mates had been sent to Galveston. The ma^es 



the nest , u.sually sitting closely upon the eggs. Occasionallv short trips for 

 food and water were made. This, in the case of the sooties, means a tremen- 

 nesTshift ^' '" ''"'^ *^^^ ordinarily leave the nest for 24 hours at the 



Records similar to the above were kept upon several different occasions 

 but the results were Identical. Summarising (1), we find that both noddS 

 and sooties, when left alone at the nest, remain on guard and brood the egg 



