22 BULLETIN : MUSEUM OF COMPAKATIVE ZOOLOGY. 



Mr. Bryant says that Heermann's Gull was " the most common species of 

 Laridce met with at Mag<lalena Bay, nearly all being in immature plumage. 

 They attend in large numbers the flocks of pelicans and cormorants when 

 fishing. They occur commonly along both coasts [of the Peninsula], breeding 

 on the islands." 



According to Dr. Streets : — ^ 



" Isla Raza is the particular breeding-place of these gulls in the gulf. It is a 

 small, low island, about three-quarters of a mile long and lialf a mile wide. At the 

 time of our visit (April), immense numbers of the birds were congregated there, 

 preparatory to laying their eggs, which, however, they had not begun to deposit. 

 We may safely say, without exaggeration, that tiiere was a bird on every square 

 foot of the ground, and others were continually hovering about overhead. Their 

 incessant noise deadened all other sounds, and so intent were they in their all-absorb- 

 ing duties of reproduction, that they seemed entirely unconscious of our presence 

 amongst them. The formation of the island is a black volcanic rock, entirely 

 destitute of vegetation. Through the long series of years during which tliese birds 

 have made it a breeding-place, there has been going on a chemical reaction between 

 the acids of their excrement and the bases of the rock, which has resulted in the 

 formation of a new substance, composed largely of a tri-basic phosphate. . . . The 

 altered rock being a softer material than the original is easily pulverized and worn 

 off by the constant attrition of the birds' feet during their breeding-season." 



Larus atricilla Linn. 

 Laughing Gull. 



Mr. Frazar appears to be the only collector who has found the Laughing 

 Gull in Lower California. He took a young female in autumnal pluuuige at 

 San Jos6 del Cabo on September 6, and on November 9, at the same place, 

 saw another bird which he thought belonged to the same species. 



L. atricilla is said to inhabit the Pacific coast of Central America, and it has 

 occurred near Mazatlan on the we.^tern coast of Mexico,* but it is not known 

 to visit California. It seems probable, therefore, that Mr. Frazar's birds were 

 stragglers from Mexico, rather than migrants from the north. 



Larus Philadelphia (Ord). 



Boxaparte's Gull. 



Larus philadelphiae Belding, Proc. U. S. Nat. Mus., V. 1883, 545 (Cape Region). 

 Larus Philadelphia Bryant, Proc. Calif. Acad. Sci., 2d ser., II. 1889, 'J51 (Cape Re- 

 gion). TowNSEND, Proc. U. S. Nat. Mus., XIIL 1890, 137 (La Paz). 



Mr. Frazar did not meet with this Gull, but it is included in Mr. Belding's list 

 of birds observed in the Cape Eegion between December 15, 1881, and May 17, 



1 Bull. U. S. Nat. Mus., no. 7, 1877, 26. 



2 Baird, Brewer, and Hidgway, Water Birds N. Amer., II. 1884, 257. 



