MONOGRAPH OF THE PETRELS. 



to be inseparable from our examples of 0. socorroensis from the same locality. The 

 dimensions of 0. chapmani are as follows : — 



Wing. Tarsus. *g*£ Cuhnen. 



£ San Benito Isl. (A. W. Anthony) . . 5.9 . . 0.95 . . 0.85 . . 0.7 



? Do. do. .. 5.9 .. 0.85 .. 0.85 .. 0.6 



O. monorJiis was discovered by the late Consul Swinhoe at Amoy. The type- 

 specimen passed into the possession of Mr. Seebohm, and was by him bequeathed 

 to the British Museum. Mr. C. B. Rickett obtained two specimens near Foochow in 

 July, and the species ranges to Japan and Eastern Siberia. Mr. Rothschild's Museum 

 contains three examples from the Gulf of the Amur, procured by the brothers Doerries, 

 and Dr. Stejneger records the species from the province of Mutsu, in Japan (Pr. U. 8. 

 Nat. Mus., XVI., p. 622). He has included the species in his list of the birds of the 

 Liu Kiu Islands on the authority of Swinhoe (P. Z. 8., 1871, p. 422), who says that it 

 had been found breeding there. 



On the Pacific coast of America this Petrel was obtained by Dr. C. H. Townsend, 

 on Socorro Island in the Revillagigedo group (Pr. U. 8. Nat. Mus., XIII., p. 134), and 

 Messrs. Grinnell and Daggett found it breeding plentifully on North and Middle Islands 

 in the Coronado group (Auk, 1903, p. 31). Mr. Anthony records it as nesting on the San 

 Benito Islands (Auk, 1894, p. 321). He states that it is much less numerous on these 

 islands than O. melania, and that while the latter species had only eggs, 0. socorroensis 

 had young by the 5th of July, and were soon away in search of food, which, as far as 

 he could discern, consisted of the young of the Rock-Lobster. It sometimes extends as 

 far as the neighbourhood of San Diego, in California, where Mr. Anthony has recorded 

 the occurrence of several specimens in May, 1895 (Auk } 1895, p. 387). 



He also observes that the brown colour of the rump and upper tail-coverts, which 

 is one of the characteristics of the species, is not constant, for occasionally the lateral 

 upper tail-coverts are white, some examples having nearly as much white on the rump 

 as in O. leucorrhoa. In his experience, about three per cent, of the specimens procured 

 showed this white on the upper tail-coverts, and both white- and sooty-rumped birds 

 were found in the same burrow. Messrs. Grinnell and Daggett noticed the same 

 variation in the colour of the rump in specimens obtained on the Coronado Islands 

 (Auk, 1903, p. 32). 



According to the last-named observers, the situation of the nests varied consider- 

 ably. Sometimes the burrows would be found in small accumulations of peat round the 

 buckthorn bushes, at other times they lay between fragments of rock where the end 

 would be impossible to reach. The shortest burrows would not exceed twelve inches 

 in length, whilst the longest zigzagged to a distance of six feet. There was frequently 

 no real construction, and a sparse flooring of fine twigs and grass sufficed for the 

 purpose of nesting. Both male and female birds assisted at the incubation. 



Two eggs in the British Museum from San Benito Island, presented by Mr. 



34 



