168 BULLETIN 121, UNITED STATES NATIONAL MUSEUM. 



we caught the sound of twittering, and traced it to a kind of mouse hole. This 

 by dint of long and tedious picking with a sheath knife we enlarged till it ad- 

 mitted an arm up to the shoulder. The work was laborious, as the floor of the 

 burrow was hard black ice and grit ; but eventually we reached the nest. At 

 the end of the little tunnel was a chamber containing a very comfortable nest 

 thickly lined with Adelie penguin's feathers, and in it a somewhat remarkable 

 collection. First we brought out an adult male alive, then an adult female, then 

 two eggs, one clean and newly laid, the other old and rotten, and under all 

 another dead and flattened Oceanites. Outside as we worked a fourth bird was 

 hovering, which when shot proved to be an adult male. 



Similar conditions were observed at the South Orknej's. Mr. Wm. 

 Eagle Clarke (1906) says: 



They appear to return year after year to the same nesting places, for both 

 eggs and dead young birds of previous seasons were numerous in the tenanted 

 holes containing fresh eggs. 



He infers that an iinnsiially cold summer may delay the nesting 

 season so that the young are not sufficiently grown in the fall to with- 

 stand the cold, and great mortality results. 



Eggs. — Only one set consisting of one ^gg is laid. Clarke (1906) 

 thus describes the eggs: "An elongated oval, dull white peppered 

 with tiny dots of reddish brown and underlying lilac, mostly accu- 

 mulated round one end of the Qgg, but occasionally sprinkled all 

 over the surface." Hall (1900) says the egg has "an almost true 

 oval form, slightly wider toward one end, around which is a circle 

 of pale pink spots." The mensurenients of 15 eggs, in various col- 

 lections, average 32.2 by 23.2 millimeters : the eggs showing the four 

 extremes measure 33.5 by 23.5, 33 by 24, 28 by 23, and 32.5 by 

 22.5 millimeters. 



Young. — The period of incubation is not known. Both sexes incu- 

 bate and, as already stated, both sexes have been found in the same 

 hole at the same time, but it is probable, as in the case of the better 

 Iniown petrels, that one sex often remains on the egg in the day and 

 the other in the night. The nestlings are thus described by Hall 

 (1900): "The nestling was covered with a uniform greyish-black 

 down. Bill black, legs bluish, tinged with faint yellow, toes faint 

 black, nails black." 



Food. — The food of the Wilson petrel consists by preference of the 

 oily substances inseparable from the profession of the deep-sea fish- 

 erman. Fish " gurry " of all sorts seem to be relished by these birds, 

 but the,y manifest the greatest eagerness when pieces of oily fish livers 

 are thrown overboard. Thej^ will, however, seize upon any morsel 

 that is cast from the ship's galley. Mr. Wm. Eagle Clarke (1906) 

 says that " Great numbers were observed around a dead whale, pick- 

 ing up morsels of fat that fell from the bills of a host of giant and 

 Cape petrels." Doctor Wilson (1907) says the food consists of minute 



