324 THE POPULAR SCIENCE MONTHLY. 



The remaining seven nests were in a mixed tangle of Virginia 

 creeper and grape-vine. These seven nests were all at a greater eleva- 

 tion than any I found in smilax or other thorn-bearing growths ; one 

 nest being thirteen feet from the ground. 



These bush-retreats of the mice were all distinctly globular, or glo- 

 boid, with the entrance usually near the rim of the original structure, 

 and looking downward. These original structures were not merely 

 covered at the top, but distinctly arched over ; and the exterior often 

 had a " pulled-to-pieces " appearance that suggested a chance accumu- 

 lation of twigs and dead leaves, rather than designed. 



A careful examination convinced me that twenty-nine were nests 

 of cat-birds, cardinal-grosbeaks, or song-thrushes, and two were nests 

 of the robin ; all of which had been built by these birds in May or 

 June of the same year — five or six months previously. The nests of 

 the robin are apparently less popular, on account of the partial or 

 complete mud-lining. 



In this series of twenty-nine nests I determined that the founda- 

 tions and lower portion of the sides, for about one half their extent, 

 were unaltered to any significant extent; and many appeared as if a 

 smaller bird's nest had been bodily removed, inverted, and so used as 

 a roof to the lower structure. Whether the rougher exterior, to which 

 I have alluded, was due to exposure since early summer, to unskill- 

 ful work on the part of the mice, or a design of these mammals to 

 render the nests less conspicuous, could, of course, not be determined. 



Eight of the series were to me quite unlike birds' nests in their con- 

 struction. The interlacing of the twigs was not like the ordinary 

 work of birds ; and the internal capacity of each one of this series 

 was much smaller than that of an ordinary cat-bird's nest ; while the 

 exterior measurements were the same or nearly so — thus showing great 

 difference in the thickness of the walls of the structure. 



Three of these eight nests I picked to pieces, and the lining proved 

 to be a mass of downy feathers — how they got them is a mystery — and 

 an abundance of the " silk " of the milkweed ; this being a material 

 not used by any of the birds I have named, and indeed not ready for 

 use until after bird-nesting is over. 



Still, I am not yet prepared to make an ex-cathedra statement that 

 these mice do build bird-nest-like structures in smilax and other dense 

 growths, without having at least the base of a bird's nest as a starting- 

 point ; yet, why they should not, does not readily appear, when we 

 remember that they build beautifully designed nests in hollow logs, 

 (ufts of grass, and under flat stones. Such nests are their ordinary 

 summer homes. 



It is certain that the materials for these summer nests, which, as a 

 rule, are on or very near the ground, are often carried from quite dis- 

 tant points ; so, why should they not carry them up a few feet into 

 tangled growths, offering almost as sure a footing as the ground itself ? 



