A number of young magpies were seen in the bushes about the river; also the nests and young of the mockingbird, (turdus orpheus, Vieil.)
The prairie-dog villages we had observed to become more frequent and more extensive as we approached the mountains; and we had now constant opportunities of contrasting the stupendous elevations of the Andes with the humble mounds cast up by this interesting little animal. We observed in the { 183} numerous burrows an appearance of greater antiquity than in those more remote from the mountains. Many of the mounds occupy an extent of several yards in diameter, though of but inconsiderable elevation, and with the exception of the present entrance, overgrown with a scanty herbage, which always marks the area of the prairie-dog villages. Indeed we have observed several large villages, with scarce a trace of vegetation about them. The food of the marmot consisting of grasses and herbaceous plants, it is not perhaps easy to assign a reason for the preference which, in selecting the site of his habitation, he always shows for the most barren places, unless it be that he may enjoy an unobstructed view of the surrounding country, in order to be seasonably warned of the approach of wolves, or other enemies.
Rattle-snakes of a particular species[133] are sometimes seen in these villages. They are found between the Mississippi and the Rocky Mountains, and appear to prefer an unproductive soil, where their sluggish gait may not be retarded by the opposing obstacles of grass and weeds. Whilst exploring Bowyer creek of the Missouri, in the spring of 1820, our party met with six or eight of them during one day's march on the prairie; and on our subsequent journey to the Rocky Mountains, we several times encountered equal, or even greater numbers, in the same space of time. This is the species of serpent which travellers have observed to frequent the villages of the prairie dogs, and to which they have attributed the unnatural habit of voluntary domiciliation with that interesting animal. It is true that the tergeminus, like many other serpents, will secure a refuge from danger in any hole of the earth, rock, or fallen tree that may present itself, regardless of the rightful occupant; but we witnessed no facts which could be received as a proof that it was an acceptable inmate of the dwelling of the arctomys.