116 
THE CONDOR 
Vol. XVIII 
length, and finally joined in two graceful curves, leaving a small pool in the 
V-shaped depression between them. The sand along the beach and spit is 
almost entirely oolitic in structure and hence lends itself exceptionally well to 
the rolling action of the waves. The crown part of Hat Island is composed of 
a hard, almost black, conglomerate. 
There was little vegetation to be found on the island and this composed 
of very few species. The only plants observed were one species of allium or 
wild leek, one cruciferous species resembling the shepherd’s purse, one species 
of the borage family, one chenopodium, one species of cactus, alfileria, and one 
of the greasewoods. The last was somewhat plentiful while the others were 
merely sporadic. 
The fauna on this island was likewise extremely limited in number of 
species. In addition to a few insects, we found only one species of 
lizard and six species of birds. The latter, in the order of their relative 
Fig. 36. California and Ring-billed Gulls on Hat Island. There are 754 birds in- 
cluded IN THE PICTURE. 
abundance, were: the California Gidl ( Larus calif ornicus), the Ring-billed 
Gull ( Larus delawarensis) , the White Pelican (Pelecanus erythrorhynchos) , 
the Great Blue Heron ( Ardea herodias treganzai), the Caspian Tern ( Sterna 
caspia), and Killdeer ( Oxyechus vociferus). Of the last we saw but one indi- 
vidual, and that was probably there as a mere visitor. The other five species 
were all found nesting on the island. 
It is impossible to give an accurate estimate of the bird population of the 
rookery on Hat Island, hence the following is intended to be merely approxi- 
mately correct. It is possibly correct within a ten per cent error. The Califor- 
nia and the Ring-billed gulls comprised a majority of the population. It is 
impossible to state with any degree of definiteness which of these two was the 
most numerous. However, from the examination of a large number of indi- 
viduals, it seemed that the California Gull was in the majority. An idea of 
the gull contingent will be had from figure 36. This picture was taken on the 
