THE MISSISSIPPI RESERVES 309 



minority, of adult birds and mammals; how 

 much and what part it plays, and in what 

 percentage of cases, in producing the colora 

 tion of eggs, is a subject which is well worth 

 serious study. As regards most of these sea- 

 birds which nest gregariously, their one instinct 

 for safety at nesting time seems to be to choose 

 a lonely island. This is their only, and suf 

 ficient, method of outwitting their foes at the 

 crucial period of their lives. 



We found only eggs in the nurseries, not 

 young birds. In each nursery there were al 

 ways a number of terns brooding their eggs, 

 and the air above was filled with a ceaseless 

 flutter and flashing of birds leaving their nests 

 and returning to them or eggs, rather, for, 

 speaking accurately, there were no nests. The 

 sky above was alive with the graceful, long- 

 winged things. As we approached the nurseries 

 the birds would begin to leave. If we halted 

 before the alarm became universal, those that 

 stayed always served as lures to bring back 

 those that had left. If we came too near, the 

 whole party rose in a tumult of flapping wings; 

 and when all had thus left it was some time be 

 fore any returned. With patience it was quite 

 possible to get close to the sitting birds; I 

 noticed that in the heat many had their bills 



