ORNITHOLOGICAL EXPLORATIONS 351 



tern along the coast. Between these and in the same direction runs 

 the river, notably the tributary Orlovka. A route following the latter 

 points directly towards Penschinsk at the innermost northeastern cor- 

 ner of the Okotsk Sea. The Stanovoj Mountains, here approaching 

 the coast, bend westward and run parallel with the coast, but at some 

 distance from the sea, as far as Okotsk ; but at the latter place, whence 

 the coast bends southwest again, that lofty mountain chain moves out 

 close to the shore. At about 55° north latitude, the mountains again 

 turn westward, the valley of Uda leaning on their southern slope. 

 Since we know that the birds alluded to do not move southward from 

 Penschinsk, through Kamtschatka, and since their escape westward is 

 effectually prevented by the snow-clad Stanovoj Mountains, the route 

 between the mountains and the coast becomes the only available road 

 to the south. Arriving at Udskij, they have the choice of at least two 

 routes. 



We shall now take one of the above species as an illustration of the 

 hypothesis here mapped out, selecting for that purpose Motacilla ocu- 

 laris, the Wagtail, with gray back in both sexes and at all seasons. We 

 remark at the outset that one specimen of this species has been taken 

 in Kamtschatka* and another one on Bering Island ; but these were evi- 

 dently stragglers, as was the specimen which was collected by Mr, 

 Belding at La Paz in Lower California. This species is a regular breed- 

 ing bird on the Tschuktschi Peninsula, and all the various parties 

 which have collected at Plover Bay obtained or observed it. It is true 

 that we know of no authentic record of this species, as distinguished 

 from the other eastern white Wagtails, having been collected at any in- 

 termediate point, but from v. Schrenck's description of the specimens 

 which Middendorfif collected at Udskij Ostrog it is clear that the latter 

 are true ocularis. But there seems to be no other possible way than 

 that indicated above, when the birds do not migrate over Kamtschatka 

 and Japan. From Udskij Ostrog they must follow the same route to 

 Dauria and Baikal which we have indicated on a i)revious page when 

 discussing the migration of Chelidon tytleri. The evidence is that the 

 species is common in the districts just mentioned, while it is missing 

 in the Amur Valley and farther east, it being undoubtedly a black- 

 backed form that occupies the Amur district. This close analogy with 



* Mr. Taczanowski now considers his previous identification erroneous, referring 

 the specimen in question to M. liigens, with which he wrongly identifies M. japovica. 

 €f. Dyb. and Tacz., B. S. Z. F. 1884, Extr., p. 11. 



