14 THE CONDOR Vol. XXIII 
nuts are mostly eaten after no more wormy acorns remain in the stores. But 
the observations pointing in this direction are too scanty to prove the sugges- 
tion. 
3. The acorn storing operation is seemingly confined to a rather brief 
period immediately following the ripening of the acorns each year. The nuts 
seem to be picked up mostly from the ground soon after they have fallen, 
though they may be taken from the trees to some extent. The acorns used in 
this locality are chiefly those of the black oak, Quercus kelloggu. 
4. Although the entire store, consisting of several thousand acorns on 
some storage trees, may be used up during a season, it may also happen that 
thousands of sound nuts in other trees are left unused and spoil from weath- 
ering and other destructive processes of nature. 
5. Suggestions as to the origin of the hole-drilling part of the habit are 
found in the way holes are sometimes still connected with cracks in the wood 
of old dead trees. Also there is some indication that hole-drilling in the bark 
of pine trees was originally done in pursuit of insects inhabiting the bark itselt. 
The fact that acorns are sometimes placed in cracks and decay cavities of dead 
_trees suggests that this sort of storage may have preceded and led to storage in 
holes made expressly for the reception of the nuts. 
6. But whatever may have been the origin of either the hole-drilling or 
the nut-storing habits, there can be no doubt that now the holes in the bark 
of living pine trees at least are mainly purposeless except as storage places for 
acorns, and that nearly all the storing is in holes made for no other purpose. 
7. The acorns stored by woodpeckers are subject to plunder by nut-eat- 
ing rodents, presumably squirrels and possibly brush rats. 
8. As to what light these observations throw on the general problem of 
the efficiency of instinctive activity, the following conclusions seem justified, 
ihe facts here presented being taken along with others made known by other 
observers. 
(a) As to hole drilling: While the holes are made expressly for the re- 
ception of acorns, many holes are probably made which are never used, holes 
are made at seasons of the year when there are no acorns to store, and large 
numbers of perfectly serviceable holes seem to be abandoned even in localities 
where both birds and acorns are abundant, and new holes are being made. 
(b) As to the storing business itself: While this is of distinet service to 
the food necessities of the woodpeckers, the instinct sometimes goes wrong 
to the extent of storing pebbles instead of acorns, thus defeating entirely the 
purpose of the instinct. Again, large numbers of acorns are sometimes stored, 
the use of which is so long delayed that the acorns become wholly or largely 
unfit for food, and this in places where the bird population seems normal. 
Finally, acorns are sometimes stored in such fashion as to make them easy 
prey for marauding rodents, when with some definite foresight and a little 
more work such exposure could easily be largely avoided. 
(c) From the facts, and the conclusions based immediately upon them, it 
Seems justifiable to conclude finally that the acorn-storing habit of this wood- 
pecker, though having much of specificness about it, is still at bottom a rather 
generalized one and perhaps on this account frequently exhibits serious mal- 
adaptations. 
ie Scripps Institution for Biological Research, La Jolla, California, November 
9, 1920. 
