18 EXPEDITION TO LAYSAN ISLAND IN 1911. 



iEstrelata hypoleuca Salvin. White-breasted Petrel, or Bonin Island 



Petrel. 



Owing to its nocturnal habits the white-breasted petrel is not so 

 conspicuous as some of the other species of its family, but it was 

 abundant in the evening. It is a fearless, dove-like creature, quite 

 amenable to petting and stroking. 



The young of this species were nearly fledged. They were to be 

 seen in the mouths of the deep burrows which completely honey- 

 comb the higher ground of the island. Tins species bids fair to 

 hold its own for some time to come, numbering 160,000. 



Bulweria bulweri (J. & S.). Bulwer's Petrel. 



In Dr. W. K. Fisher's report of the Birds of Laysan Island, 1902, 

 he states that he did not detect any Bulwer's petrels on Laysan. We 

 were, therefore, somewhat surprised to find tins species rather abun- 

 dant, and at the same time of year that Dr. Fisher was there. 



In the cracks and crannies of the rocks on the south end of the 

 island one was sure of finding these birds, and in almost every case a 

 pair of birds would* be in the same opening. We found them also on 

 other parts of the island, wherever there were pieces of phosphate 

 rock or coral under which to crawl. 



While we were after some specimens of coral rock, we were much 

 surprised to find one of these quiet little birds sitting in the debris 

 that had fallen from the under side as we applied the sledge hammer 

 from above. The pieces had dropped in such a manner that, not- 

 withstanding the falling of a piece weighing 75 pounds or more, the 

 bird was unharmed and apparently not alarmed. Under the bird 

 we found a fresh egg. This incident occurred on the 2d day of 

 June, and although we had previously seen many of these birds, we 

 had not found any eggs. Upon further investigation we found 

 that the birds on the south end of the island had eggs, all of which 

 were fresh. In some nests we found both birds sitting side by side. 

 We estimated the number of this species to be 1,000. 



Oceanodroma tristrami Salvin. Sooty Petrel. 



The sooty petrel is not a common bird on Laysan. Near the 

 south end of the lagoon a number of young birds were found, all 

 dead or in a dying condition. They were fully fledged, retaining 

 only traces of down. A diligent search procured but two adult 

 birds. These birds were so much smaller than the measurements 

 given by Mr. Ridgway for this species that there was at first some 

 question as to their identity. 



The following table gives Mr. Ridgway's measurements, also those 

 of the specimens referred to above: 



