22 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Mr. Bryant says that Heermann’s Gull was “the most common species of 
Laride met with at Magdalena 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: —? 
“Tsla 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 half 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 there 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 these 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 Liyy. 
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 plumage at 
San José 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 western 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 (Orp). 
BoNAPARTE’S GULL. 
Larus philadelphiae Beipine, Proc. U. S. Nat. Mus., V. 1883, 545 (Cape Region). 
Larus philadelphia Bryant, Proc. Calif. Acad. Sci., 2d ser., II. 1889, 251 (Cape Re- 
gion). TcwnsEnp, Proc. U. S. Nat. Mus., XIII. 1890, 187 (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 Region between December 15, 1881, and May 17, 
1 Bull. U. S. Nat. Mus., no. 7, 1877, 26. 
2 Baird, Brewer, and Ridgway, Water Birds N. Amer., II. 1884, 257. 
