What Some Animals Know About Topography 



John C. Branner 



Professor of Geology, Stanford University 



Credit is often claimed for the superior intelligence and scientific 

 attainments of engineers in overcoming problems in the building of 

 roads, railways, and aqueducts across mountainous regions. I 

 have often noticed, though, that animals other than man know a 

 thing or two about such matters. Anyone who has had to travel 

 much with pack-mules or donkeys in hilly or mountainous regions 

 must have noticed that such an animal, when left to himself to 

 climb a long steep hill, knows how to zig-zag so as to get as easy a 

 grade as possible, quite as well as an engineer. 



Birds are evidently so far above the surface irregularities of the 

 earth that they are supposed to be quite independent of topography. 

 That independence, however, probably belongs only to very high 

 flying birds. At least I was led to think so by watching the flight 

 of robins on their way south in the fall of 1882 in the South 

 Mountains of Pennsylvania. 



In the latter part of the month of October, 1882, I was working 

 on the topography of the mountains along the south side of the 

 Cumberland Valley and thirty or forty miles north of the town of 

 Gettysburg, Pennsylvania. The region was covered by heavy 

 forests, but the trees were already bare of leaves, and the woods 

 were just then full of robins on their way south. In surveying 

 lines several miles in length through the forests I was struck by the 

 fact that the robins were not all flying in the same direction, though 

 they all went in the same general direction at any one point. If I 

 stopped long at one place the robins were all seen to be moving, by 

 their usual short and dilatory flights, toward the south; at another 

 place they were moving toward the southwest ; and at still another 

 point they were moving toward the northeast. At first the flight 

 toward the northeast puzzled me, for they were clearly not the 

 accidents or individual variations in direction that one may see in 

 the general movements of robins. So at first I concluded that 

 birds sometimes made mistakes just like people. Later I found 

 that the birds knew more about their business than I did, for I 

 learned that where the birds were flying toward the northeast, the 

 gap was always near by, but when they were flying toward the 

 southwest the gap might be either near or far. At first I was much 

 puzzled by these differences, but on climbing to the tops of some of 



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