MILL CREEK. 205 



cupied, and I believe the full number of individuals oc- 

 cupying them was ascertained. In most cases I captured 

 every individual and released them. 



Of the series, thirty-one nests were placed in a dense 

 tangle of smilax or green -brier. None was near the 

 surface of the thicket, but usually about one-third the 

 distance from its uppermost surface ; for instance, if the 

 thicket was six feet high, the nest would be at an eleva- 

 tion of four feet, or very near it. This was a very uni- 

 form feature of the nests examined, and if the mice 

 merely occupy old nests of birds where they find them, 

 indicates a uniformity in the matter of nest-building of 

 which I was not aware. 



Again, the smilax was so very dense, or closely inter- 

 woven, that it seemed to me impossible that a bird as 

 large as a robin or cat-bird could have penetrated it. 

 Perhaps the continuous growth of the vine, after the 

 birds abandoned the nest, made it inaccessible to them 

 by early autumn. I did determine one interesting fact 

 about the impenetrability of these growths of green- 

 brier that the small hawks found sparrows and the 

 mice quite inaccessible when they took refuge therein. 

 In one case, a sharp - shinned hawk, a little more rash 

 than usual, struck at a snow-bird as it dived into the 

 smilax, and instead of capturing it, was himself hope- 

 lessly entangled. At least, before he could extricate him- 

 self, I was able to secure his hawkship. 



Four of the forty-two nests were among blackberry 

 canes, and this growth also was exceedingly dense and 

 difficult to penetrate. The remaining seven nests were 

 in a mixed tangle of Virginia creeper and grape. These 



