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Show 310 MR. W. H. HUDSON ON THE BURROWING OWL. [May 19, though old and dried up as a bit of parchment. This I have often seen them do. Though the Owls are always on familiar terms with the Vizcachas, and occasionally breed in one of their neglected burrows, they generally excavate their own burrows. The kennel is crooked, and varies greatly in length, from 4 to 12 feet. The nest is at the extremity, composed of wool and dry grass, often exclusively of horse-dung. The eggs are five, white, and nearly spherical. After the female has begun laying, the birds continue to carry in dry horse-dung, until the floor of the burrow and a space before it is thickly carpeted with this material. The following spring the loose earth and rubbish is cleared out; for the same burrow may serve them two or more years. It is always untidy, but mostly so during the breeding-season and when prey is very abundant, the floor and ground about the entrance being often littered with excrements and pellets of hair and bones, wing-cases of beetles, and feathers, hind quarters of frogs in all stages of decay, the great hairy black spiders of the pampas, and remains of half-eaten snakes and other unpleasant creatures they subsist on. But all this carrion about the Owl's disordered house reminds one forcibly of the important part assigned to it in the natural economy. The young birds ascend to the entrance of the burrow to bask in the sun and receive the food their parents bring: when approached they become irritated, snapping with their beaks, and appearing reluctant to enter the burrow; but for some weeks after learning to fly they make it their refuge from danger. Old and young birds often live four or five months together. I believe nine tenths of the Owls in this country make their own burrows ; but as thay occasionally prefer breeding in the forsaken burrows of mammals to mining themselves, it is probable they would almost always observe this last habit did suitable burrows abound. I have never seen any complete account of the North-American form of this Owl, but presume its habits are now well known, as all matters connected with science receive so much attention in that country. From such stray notices of the bird as I have met, I learn that it inhabits and invariably breeds in the kennels of the Prairie- Marmot. The small, neat burrows of that mammal must be far better suited to its requirements than the vast ones excavated by the Vizcacha. Probably the Burrowing Owl originally acquired the habit of breeding in the earth in open level bare regions; and when this habit (favourable as it could not but be in such shelterless places) had become ineradicable, a want of suitable burrows would lead it to clean out such old ones as had become half filled with rubbish, to deepen such as were too shallow, and ultimately to excavate new ones. In Buenos Ayres the mining instinct varies greatly in individuals. In the birds that breed in Vizcachas' burrows the instinct is doubtless weak ; they can hardly be said to possess it. Some pairs, long mated, only begin their burrows when the breeding-season is already on them ; others make their burrows as early as April-that is, six months before the breeding-season. Gene- |