July, 1922 ACTIVITIES OF THE CALIFORNIA WOODPECKER 117 
ter of holes at the upper, or black oak elevation is not less than 20 mm. 
The following table gives the diameters of ‘‘random sample’’ holes on three 
trees at the lower elevation where live oaks largely prevail: 
13 mm. 16 mm. 20 mm. 22 mm. 
ist tree 35 holes 11 holes 14 holes 1 hole 
2nd tree 46 holes 16 holes 14 holes 1 hole 
3rd tree 53 holes 8 holes 1 hole 1 hole 
These measurements make it in the highest degree probable that, in general, 
smaller holes are made for the slimmer live oak nuts. The quantitative data 
were obtained on my visit of August 27-28, 1921, which was before the year’s 
harvest began; so very few indeed of the holes on the trees examined contained 
nuts or even remains of nuts. 
But the visit of November 19-20, shortly after the harvest was completed, 
furnished the clinching information, for one storage at least. This tree was well 
down to the edge of the pine zone, consequently where live oaks largely predom- 
inate. I copy from my notes almost verbatim: ‘‘An enormous number of nuts, 
apparently all of live oak, many of them in brand new holes. Vast majority of 
the holes small, just large enough to admit the slim nuts. A few larger holes 
scattered among the small ones, but none of them so far as I can see containing 
nuts. This distribution of size of nuts relative to size of holes is very striking. 
Not infrequently the long slim nuts put side-wise into chinks in the bark; but 
seemingly never into the large holes.’’ 
That there are real advantages in this fitting of hole size to acorn size there 
ean be little doubt. For one thing acorns which fit snugly into clean-cut holes as 
was especially the case in this tree, would be better protected against both rain 
and marauding mammals than would those merely thrown, so to speak, into 
over-sized, ragged holes. 
Again, there would be a saving of labor in the making of holes no larger 
than the actual necessities call for. It must be confessed, however, that in view 
of the abundant evidence of fruitless work by these birds, one may well question 
the potency of this advantage. It does seem, though, that it may count for some- 
thing when the hole drilling has to be done in the bark of the live oak, which is 
much harder and rougher than is the pine bark. And there is no question that 
in the field of these observations, the live oak holes made for acorns of the same 
species, present this size adaptation. 
The question of how such an adaptation is brought about is important but 
impossible to answer because of the meager information. Two possible approxi- 
mate explanations suggest themselves. First: One and the same bird may pass 
back and forth between the black oak and the live oak regions and drill large 
holes while in the former and small holes while in the latter. Second: One set 
of birds may become localized in a black oak region and another set in a live oak 
region, so that holes of different sizes as noted would be the work of different 
birds. On the basis of what we know in general about the intelligence of these 
birds, the latter explanation would seem most probable; but it is at this point 
that information fails us. 
The birds surely do not restrict their acorn-gathering to oaks in the immedi- 
ate vicinity of the storage trees. There is evidence of several sorts to this effect, 
the most conclusive of which is the fact that I have seen them in the act of carry- 
ing nuts for a distance of half or three-quarters of a mile. But this distance is 
