﻿ON A NESTING PLACE OF SULA SULA (L1NN/EUS) AND 

 STERNA AN/ESTHETA SCOPOLI. 



By Dean C. Worcester. 



On Saturday, June 15, 1907, when on a trip of inspection to the 

 Babuyanes and Batanes Islands in company with the Governor-General, 

 our party sailed from Port San Pio on the Island of Camiguin in a 

 general northwesterly direction in order to observe a volcano said to 

 exist in the immediate vicinity of the Didikas rocks. 



We found that this volcano, which rose from the sea in 1859 and 

 gradually increased in size until it attained a height of 700 feet, had 

 completely disappeared. 



The Didikas rocks consist of three separate masses, two of which rise 

 to a height of about 150 feet each and are quite sharply pointed, while 

 the third mass is longer, lower, and runs up to a narrow crest (PI. I). 

 There were signs of recent volcanic activity on the western side of this 

 lower mass of rock ; and as the sea was perfectly calm at the time, we at- 

 tempted to land in order to make a closer examination. As our boat 

 approached the rocks large numbers of boobies [Sula sula (Linn.)] and 

 terns (Sterna ancestheta Scop.) flew out to meet us and hovered about 

 our boat in evident curiosity. They were little disturbed by the shots 

 that ended the earthly careers of several of their number, and continued 

 to follow us about as long as we remained in the immediate vicinity of 

 the rocks. 



The two higher pointed rocks were covered with the excrement of the 

 boobies, and as a number of terns were seen issuing from holes in the 

 volcanic conglomerate which made up a part of the third rock, it seems 

 probable that both species use these rocks as a nesting place. 



The Didikas rocks lie fairly in the main typhoon track and are swept 

 by fierce winds and strong currents. There is no more isolated and inac- 

 cessible breeding ground for water-birds in the Philippine Islands. Even 

 with the sea apparently perfectly calm, it proved impossible to land, as 

 the almost imperceptible swell was breaking so heavily at the base of the 

 rocks that there would have been serious clanger of destroying our boat 

 had we attempted to do so. 



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