MIGRATION AND NESTING OF THE SAGE THRASHER
THIS bird, Oroscoptes montanus, was a favorite of mine from boyhood, tho I saw little of him, merely a passing acquaintance, as it were. He seemed to attend strictly to his own business, that of migrating, but was never nervous or flurried. He apparently never had time for frivolities or any side trips, tho I can't say that he hurried on his way. He would run to a bush, halt an instant, and then on to another. If bushes were far apart he would sometimes fly from one cover to another, halt, and then forward again. A worm in the interval, did not turn him aside; he would swallow it and move on. He knew just where he was going, and while in no haste to arrive, was not to be diverted from the straight and narrow path. He seemed to be aware that a straight line was the shortest distance between two points, and even if pursued could not be forced many points off his course.
These were my earlier impressions of his character and caused much interest and some observation of his migrating. These few notes on the travels of the sage thrasher were made in southern California and include territory about thirty-five miles long and three or four wide, San Gorgonio Pass, extending from Palm Springs on the Colorado desert, 500 feet elevation, to the summit of the Pass, 2500 feet elevation.
At Palm Springs the thrashers usually appeared about the middle of January, tho I have seen them there during the latter part of December. They came in from a southeasterly direction, across the desert, moving from bush to bush as I have described. Their rate of travel seems very slow in view of the fact that they always appear to be moving forward. Some seasons they would be a month in traversing the thirty or thirty-five miles, a speed of about a mile per day. I am satisfied that this is their average speed across the country I have mentioned, as I have observed it on short distances as well. I have seen the birds at all points between the two localities named, and the dates of observance practically coincide with the estimated speed of travel. I have noticed the birds five or six miles east of town and a week later they would appear a mile or two west of town. I walked a mile and a half to school, to the east of my home, and would see the first birds in the morning at the school end of the line. On my way home in the evening I would overtake them about a mile from where I had seen them earlier in the day.
Now I do not pretend to give these figures as an estimate of their rate of travel during the entire migration. To do so would be absurd, as their destination is so far from where I observed them. At a mile per day they could never reach their nesting place, raise a family, and get back to winter quarters. I do not know the nearest point where their nests may be found; but from some experience in their nesting haunts in southwestern Colorado, I believe some parts of the Mojave Desert would be promising.
In forming any theory of migration so much data is necessary that I hesitate. Any one, however, has some right to an opinion, and mine is that the sage thrasher migration is local rather than general. I have never seen them on their return trips in the autumn and some seasons they have failed to materialize in the spring movement. I saw them in their nesting places in Colorado as late as October 30, and judging from movements of some of our California birds in perpendicular migrations, these thrashers would not go to the Mexican line to spend the winter.
