28 
THE CONDOR 
Vol. XV 
local breeding places at least may not be fixed from year to year. There is con- 
siderable shifting, this irregularity being concurrent with varying food supply. 
To illustrate: in case there has been in a certain mountain range an abun- 
dant acorn crop, sufhcient to last throughout the winter, any flock of pigeons 
foraging there would be likely to linger on until the advent of the usual season of 
nesting. These pigeons would thus be more likely to remain there and breed 
that particular season, zonal conditions being favorable, than to move off to an- 
other mountain range. Such an explanation would appear to account for the 
vacillating numbers of breeding birds in the various more or less isolated moun- 
tain ranges of southern California. 
Relative Numbers, Past and Present 
It has been found practically impossible to estimate relative numbers of pige- 
ons now as compared with any former period. This difficulty results from the 
variability from year to year in the degree of concentration of the birds in limited 
areas, and further from the sporadic distribution at any season. Reports of ob- 
servers, therefore, no matter how explicit they may appear, cannot be used fairlv 
in such inductions. 
In fact, no single statement previous to that of Chambers (1912, p. 108) 
would lead to the inference that pigeons were ever more numerous than last year. 
But taking the above considerations into account, no significance can be given to 
such isolated statements. The literature examined gives no exact data ; but we 
can, nevertheless, be morally certain that there has been a very great decrease in 
tbe numbers of pigeons since the early days of western settlement, when game of 
all sorts was so abundant as to arouse but little comment. 
Food of the Pigeon 
As already intimated, the amount of food available to the pigeon appears to 
be tbe main controlling factor in distribution, aside from zonal considerations. 
This is more particularly true in winter, though probably to some extent in sum- 
mer also. As will be observed from the following data, the food consists chiefly 
of berries and nuts, of intermittent productiveness. A large crop one year in a 
certain region is almost sure to be followed by a barren year. So that the pige- 
ons would fare poorlv if dependent closely on" any one single locality. Their pro- 
clivity for circulating over large areas makes available to them the abundant crops 
recurring at different places. The birds in great numbers are thus able to find 
support somewhere all the time. 
Out of twenty-two records, ten give acorns as the chief article of diet. Prob- 
ablv all the species of oaks are patronized by the pigeons. Those especially re- 
corded are: in west-central and southern California, the live oaks (Qnercns agri- 
folia and 0 . zvislhenii) , in the foothill regions, the golden oak (Ouercits cJiryso- 
lepis), and along the Sierra Nevada and on the San Bernardino and San Jacinto 
mountains, the black oak (Quercns kelloggii). The acorn season lasts well 
through the autumn months, and under favorable circumstances even until Feb- 
ruary. 
As with all other food, the acorns are swallowed whole in such numbers that 
the crop becomes at feeding time enormously distended. In this dilation of the 
gullet the food is acted upon by the powerful digestive juices, and both shell and 
kernel rapidly disintegrate and pass on to the stomach and gizzard. There is no 
disgorgement of hard parts of the food, as with some birds. Considering the ap- 
parent small size of a pigeon’s mouth, an amazing thing is its ability to swallow 
