May, 1904 I 
THE CONDOR 
69 
nests — they were made largely of small stones! Where the nests were in cracks 
or holes in the faces of boulders, the stones were usually merely mixed with the 
sticks and weeds of the nest itself, but in one case where the nest was in a crack 
of a slanting boulder over which four-footed egg hunters might make their way, 
the stones were piled up in front along the edge of the crack leaving little room 
for any but the owner to enter. This was also the case with a ne.st placed in the 
crack of a cut bank. 
The most curious feature about the use of the stones was that where the site 
admitted, there was generally a mass of stones leading away from the nest — like a 
gravel walk from a door. One of the two ground nests that we found — built so far 
back under a rock that the young could be seen only when they raised their 
heads for food — had a striking pavement. On counting the stones of walk and 
entrance, I was surprised to find that there were fift\’, and there were doubtless 
many more mixed in with the materials of the nest. The stones, like most used by 
the wrens were bits of sandstone, var3ung from half an inch to an inch and a half 
ROCK WREN NESTS IN FACE OF BOULDER 
in length. Those in figure 2 are quite characteristic, although they are not so 
flat as many that are used. One nest in a hole in a rock about three feet from the 
ground, had a wide entrance paved with them very much like that of figure 2. 
Eighty-three stones were counted here, and there were many more mi.xed in with 
the mass of the nest. The largest number that I counted belonged to the nest 
shown in figure 2. It had two hundred and sixty stones, none of them less than 
half an inch in length! In addition to the stones and the .soft gra.ssy nest lining 
there was a quart can full of coarse sticks, many of them four or five inches long 
and as large around as a lead pencil. This nest is now on record in the National 
Museum. 
Two possibilities suggest themselves in explanation of this astonishing work 
of the wrens. In a general way it is in line with the wrenish habit of making 
bulky nests — a matter of protection perhaps, like the great accumulations of the 
wood rats. In special cases where the entrance to the nest is partially" closed by 
the stones, the purpose can be easily understood. Protective reasons do not apply, 
however, to the masses of stones leading away from the nest, sometimes as far as 
