MONOGRAPH OF THE PETRELS. 



" Erebus " and " Terror " Expedition procured this Petrel off Mt. Erebus, in February, 

 1841, and on the following day at the nearest point they reached to the Magnetic 

 Pole (Salvin, Cat. Birds Brit. Mus., XXV., p. 420). 



The nest, consisting of a few small stones and a little earth, is placed under rocks, 

 in caves, or the crevices of steep cliffs facing the sea, at altitudes varying from a few 

 feet to several hundred feet above the sea level. 



The single white egg is laid in December, and young birds have been taken at the 

 end of January. The parents, when approached, do not fly away, but retreat a short 

 distance and defend themselves by ejecting at the intruder, to a distance of from six 

 to eight feet, the oily contents of their stomach. The smell is most offensive, and clings 

 for days to any material with which it comes in contact. Eggs measure : Axis, 

 2.01-2.38, diam., 1.35-1.67. 



Both sexes. Snowy-white : " bill black ; feet and webs grey ; iris dark brown " 

 (Hanson). 



Male. Total length, 14-16 inches ; culmen, .8-1.05 ; wing, 10.1-12 ; tail, 4.3-5.1 ; 

 tarsus, 1.3-1.5. 



Female. Total length, 14 inches ; culmen, .7-.95 ; wing, 9.8-11.8 ; tail, 5.2 ; 

 tarsus, 1.5. 



Dr. Bowdler Sharpe, in his report on the collections of the " Southern Cross " 

 Expedition (p. 149), points out that the extraordinary variation in size exhibited by a 

 series of the Snowy Petrels is not due to a difference of sex, the males measured 

 by him having a wing of 10.1 to 11.8 inches, and the females 9.8 to 11.8 inches. 

 The variation in size of bill, too, is also very marked, and is not a sexual distinction. 



Several specimens in the British Museum series have the outer web of the first 

 primaries somewhat dusky, especially towards the end of the quill ; these are probably 

 young birds. 



The male and female described were captured in the Pack Ice during the voyage 

 of the " Southern Cross." The specimen figured is from the Ice Barrier, and was 

 procured by the " Challenger " Expedition. 



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