478 FIELD STUDY IN ORNITHOLOGY. 



of Midch'ii<l(»rff among- the Saniojeds, who know how to reach their 

 goal by the shortest way tlirou.uli phices wholly strange to them. 

 He had known it among dogs and horses (as we may constantly per- 

 ceive), but was surprised to find the same incomprehensible animal 

 faculty unweakened among uncivilized men. Nor could the Samojeds 

 understand his inquiry how they did it. They disarmed him by the 

 question, How now does the Arctic fox find its way aright on the tun- 

 dra, and never go astray? And Middendorft' adds, "I was thrown 

 back on the unconscious performance of an inherited animal faculty;" 

 and so are we! 



There is one more kind of migration, of which we know nothing, and 

 where the held naturalist has still abundant scope for the exercise of 

 observation. I mean what is called exceptional migration — not the 

 mere wanderings of waifs and strays, nor yet the uncertain travels of 

 some species, as the crossbill in search of food, but the colonizing 

 parties of many gregarious species, which generally, so far as we know 

 in our own hemisi)here, tra\'el from east to west, or from southeast to 

 northwest. Such are the waxwing {Ampelis garrnld), the pastor star- 

 ling {Pastor 'rosciis), and Pallas's sand grouse, after intervals sometimes 

 of many years, or sometimes for two or three years in succession. The 

 waxwing will overspread western Europe in winter for a short time. 

 It appears to be equally inconstant in its choice of summer quarters, 

 as was shown by J. Wolley in Lapland. The rose ])astor regularly 

 winters in India, but never remains to breed. For this piu-pose the 

 whole race seems to collect and travel northwest, but rarely, or after 

 intervals of many yciirs, returns to the same quarters. Yerona, 

 Broussa, Smyrna, Odessa, the Dobrudscha have all during the last 

 half century been visited for one sunuuer by tens of thousands, who 

 are attracted by the visitations of locusts, on which they feed, rear 

 their young, and go. These irruptions, however, can not be classed 

 under the laws of ordinary migration. I^ot less inexplicable are such 

 migrations as those of the African darter, which, though never yet 

 observed to the north of the African lakes, contrives to pass, every 

 spring, unobserved to the lake of Antiocli in North Syria, where I 

 found a large colony rearing their young, which, so soon as their 

 ])rogeny was able to tly, disappeared to the southeast as suddenly as 

 they had arrived. 



There is one possible explanation of the sense of direction uncon- 

 sciously exercised, which I submit as a working hypothesis. We are 

 all aware of the instinct, strong both in mammals and birds without 

 exception, which attracts them to the place of their nativity. When 

 the increasing cold of the northern regions, in which they all had their 

 origin, drove the mammals southward, they could not retrace their 

 steps, because the increasing polar sea, as the Arctic continent sank, 

 barred their way. The birds reluctantly left their homes as winter 

 came on, and followed the supply of food. But as the season in their 



