206 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



lined with small broken bits of the same material. The birds seem 

 to be much tamer here than elsewhere. 



Eggs. — The Caspian tern raises but one brood in a season and lays 

 from two to four eggs; two seems to be the commonest number, 

 especially so in southern colonies ; three eggs are commoner in north- 

 ern colonies, where this number seems to prevail ; four eggs are very 

 rarel}^ found. The eggs are distinctive and are more like gulls' 

 eggs than other terns' eggs. In shape they are ovate or elliptical 

 ovate. The shell is lusterless and sometimes rather rough. The 

 ground color varies from " pinkish buff " or pale " warm buff " to 

 very " light buff " or " cartridge buff." They are usually rather 

 sparingly marked, sometimes evenly with small spots, sometimes with 

 scattering large spots or irregular blotches, and occasionally with a 

 few fantastic scrawls. The markings are in the darker shades of 

 brown, " raw umber," " auburn," " mummy brown," or dark " sepia." 

 The lighter types are often indistinctly spotted with " pale violet 

 gray," or " lilac gray." The difference between these eggs and those 

 of the roj^al tern is more easily seen than described. I think I could 

 pick them out every time. The measurements of 48 eggs, in the 

 United States National Museum and in the writer's collections, aver- 

 age 64.5 by 45 millimeters; the four extremes measure 73 by 44.5, 

 62.5 by 48, 58.5 by 45.5, and 64.5 by 42 millimeters. 



About 20 days is said to be the period of incubation. Probably 

 both sexes incubate, as is commonly the case with related species. 

 Perhaps under favorable conditions, when the sun is not too hot, 

 the eggs may safely be left for a time to be kept warm by the sun; 

 the birds are sufficiently sensitive to changes in temperature to 

 recognize such conditions. 



Young. — Mr. Arthur has sent me some very interesting notes on 

 the behavior of young Caspian terns in the colony referred to above, 

 from which I quote as follows : 



Before the motor boat reached the shore it was quite evident that there were 

 a number of young on tliis island, as the noisy approach of our boat caused 

 the little ones to take to the water and swim rapidly away. In their aquatic 

 journey the young terns were followed by their perturbed parents, who hov- 

 ered in the air uttering hoarse cries. I landed and discovered a few of the 

 smaller terns hiding in the grass and a number of eggs scattereil on the 

 rim of the shell. The Caspian terns who had eggs on the island were the first 

 to return, soon followed by those parent birds whose young had taken to the 

 grass for the purpose of concealment. While it is true that the majority of 

 the small Caspian terns had taken to the open gulf and the distracted parents 

 still hovered over them, I noted with my glasses that they were now guiding 

 their babies back to the oyster shells that the little ones called home. The 

 larger of the small terns showed in no little way their adaptitude for swinnuing, 

 for a number of them were from one-fourth to one-half mile away, and I 

 could see them being tossed up and down upon the salt waters, as there was 



