214 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



impelled by a common impulse, with a great roar of thousands of 

 wings, a dense cloud of screaming birds, and a bewildering moving 

 picture of flashing black and white. As the birds were shy my 

 attempts at photography resulted in only a few distant snapshots 

 of the colony as a whole ; so I set up my blind in the midst of the 

 colony and left it overnight for the birds to get accustomed to it. 



On my return the next morning I was delighted to find that the 

 terns had learned to regard my blind as harmless and had settled 

 down on their nests all around it. Walking up to the blind, with 

 two companions, I concealed myself inside of it with my cameras, 

 and the other two men walked away. The birds, thinking that all 

 of us had gone, immediately returned and assumed their regular 

 vocations. For two or three hours I sat there unobserved and 

 watched the activities of that populous colony. All around me the 

 flat sandy plain was dotted with eggs, a single egg in each little 

 hollow in the sand at regular distances, just far enough apart so that 

 the birds could not touch each other when sitting. It was a hot, 

 sunny day, probably too hot for the eggs to be left uncovered, so 

 the birds spent most of their time incubating; but there were many 

 birds standing beside their sitting mates. There was not sufficient 

 difference between the sexes for me to determine whether both sexes 

 incubate or not, but probably they relieve each other occasionally. 

 There were no young in the colony, so I could not study their 

 method of feeding them. Life is never dull in a large bird colony 

 and the birds are never still; some were coming and some were 

 going all the time ; there was a constant babel of voices and numerous 

 little squabbles occurred, if an incoming bird alighted too near its 

 neighbor. They were so close together that they could hardly spread 

 their wings without interfering. An air of nervous excitement 

 seemed to pervade the colony all the time, as in a crowd of women at 

 an afternoon tea, and at frequent intervals, without any apparent 

 cause, a large portion of the colony would rise suddenly and simul- 

 taneously, as if frightened, fly around for a minute or two, all 

 screaming excitedly, and then all would settle down again as if 

 nothing had happened. 



I counted the nests in a measured area and then roughly measured 

 the whole colony, from which I estimated that it contained, at least, 

 3,500 nests. There were a hundred nests in a space four yards 

 square; certainly this was a densely packed colony of a highly 

 gregarious species. 



The colony described above may be considered as typical of the 

 species, which almost always nests in similar situations in closely 

 populated colonies. The nest is nothing more than a slight hollow 

 in the sand, without any attempt at a lining. I believe that the 

 normal set consists of two eggs ; very rarely three are found and four 



