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4 THE CONDOR Vol. XXIII 
Although unusual animal performance like this is sufficient in itself to 
excite interest and elicit careful inquiry, the thoughtful naturalist is hkely 
to be more attracted to particular phenomena by their probable bearing on 
some general problem in which he is interested, than by their uniqueness. The 
broader problem which, in this instance, has been the leading motive of my 
observations, is that of the efficiency of instinctive activity. How thoroughly 
do such practices meet the needs of the animals which perform them? In 
other words, how near to perfection is their adaptiveness? 
Two early cursory observations raised the conjecture that the habit of 
the California Woodpecker might, if followed up, yield enlightening facts 
on this question. One of these was the very large number of holes I had seen 
in some trees. Thus, fifty feet of a prostrate pine tree which I saw in the San 
Jacinto Mountains several years ago, contained, according to an estimate 
made with considerable care, 31,800 holes. The query easily arises, Is every 
hole in such a ease actually used as the receptacle of a nut? The account which 
follows will bring out rather convincing testimony on this question. 
The other and much more striking fact bearing on the general problem of 
adaptiveness, was brought to my notice by Dr. Grinnell. It is that oceasion- 
ally the woodpeckers gather pebbles instead of acorns and place them in the 
holes. The first instance of this which came to my attention consisted of a 
considerable section of a barkless oak log now in the Museum of Vertebrate 
Zoology at Berkeley (Fig. 2), in which there is a large number of holes nearly 
all of which contain pebbles. This specimen, which came from Sonoma Coun- 
ty, California (where there are no pine trees) is conclusive proof to Dr. Grin- 
nell that the pebble-storing as well as the acorn-storing is the work of wood- 
peckers. Grinnell tells me that he looked into the matter at the time the 
specimen was received and found that the location of the tree and other con- 
ditions were such as to preclude any likelihood that the work was done by 
humans. Nor is there any other animal resident in that locality to which the 
performance could be attributed with any degree of probability. 
Nor does this case of pebble-storing stand alone. Mr. C. R. Orcutt, a 
naturalist of wide experience in the southwest, has recorded a similar instance 
observed by him in Lower California (‘‘Stones placed in pine-trees by birds’’. 
Science, March 14, 1884, p. 305). The trees (Jeffrey pines) were in this in- 
stance situated at an elevation of 6,000 feet and in an almost uninhabited re- 
gion, so there was practically no chance for the stones to have been put where 
they were by human hands. 
OBSERVATIONS 
During a holiday outing at Cuyamaca reservoir, San Diego County, Cali- 
fornia, July 3-5, 1919, I found numerous pines (Jeffreys) used by the wood- 
peckers as storage trees. Some of these contained a large number of holes, 
the great majority of which were filled with acorns of the black oak (Q. kel- 
loggw), the prevailing oaken neighbors of these pines. But while some of the 
trees were thus well stored, others had only a fraction of the holes acorn- 
filled; and two trees in particular, as thickly punctured as any I have ever 
seen, contained not a single acorn or any litter roundabout indicating that 
the birds had given the trees the least attention for many a month. 
One of these abandoned granaries struck me as specially interesting from 
the fact that many of the holes, though not new, were to all appearances in 
perfect condition for the reception of nuts; and the further fact was clear 
