PKOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 53 



a region be deprived of its spring birds " proves very strikingly tbe tact 

 that over a wide range of latitude each individual resorts for propaga- 

 tion to the latitude where it was hatched ; that birds quit their winter- 

 quarters in succession as their individually more northerly home becomes 

 habitable, — naturally the most northerly latest; and that, consequently, 

 Middendorf's calculation of the rate of migration-flight must be falla- 

 cious, because the individuals he observed earlier in spring at a lower 

 latitude were not the same he saw later not thirty degrees higher north, 

 but w^ere such as passed over the former, whilst they perhaps were be- 

 ginning to construct their nests; therefore, the period that lay Ijetween 

 observing the two could not be made use of as a measure Avhereby to 

 determine their pace of flight or advance during a day. 



That the direction of the course of wandering birds should be influ- 

 enced by river courses or mountain chains, is a point which I do not 

 agree to, at least so far as Europe comes under contemplation. Here 

 during the fall, the route of miscellaneous species is so varied that the 

 two i)rincipal hosts cross each other at right angles ; one great mass 

 progressing due west from the farthest east of Asia (e. g., Anthus rich- 

 ardi, Sylvia supercUiosa), and continue their course to Heligoland, Eng- 

 land, France, and Spain. Besides these, all the rare autumnal visitors 

 come here from the far east of Asia, which proves that there must be 

 with birds of these regions a strong inherent tendency to a western mi- 

 gration, even in species whose real winter-quarters are in the south of 

 India down to the Sunda Isles, as, for instance, the two named above. 

 This line of flight diverges abruptly to the north when approaching 

 the Atlantic in England, Western France, and Spain ; vide the immense 

 numbers crossing the Straits of Gibraltar. 



This westerly current is cut at right angles by another host coming 

 simultaneously down from the extreme north of Euroi^e and Asia, and 

 steering due south for their winter-quarters, viz : The Willow Warblers, 

 Phylloscopus trocMlus and riifus, which go from the North CJape of Scan- 

 dinavia to the Cape of Good Hope ; P. tristis and boreaUs, from Northern 

 European and Asiatic Eussia down to the south of India and China. 

 The latter, together ^vitl\ Falco rnfipes, MotaciUa citrcola, Anthus cervimts, 

 Emheriza aureola., and Limosa cinerea, all plentifully breeding so close to 

 Heligoland as the Onega Dvina, Megin, and Petchora districts, but still 

 never, or very rarely, turning up here during their autumnal flights, 

 proves in itself their southern course — without the least western incli- 

 nation — even if they were not observed down the Ural, the Black Sea, 

 Turkestan, &c. The most striking instance of such a move is seen in 

 Sylvia philomela, which breeds in the south of Sweden, and, neverthe- 

 less, has been observed here but once during the last forty years! 



A few can be pointed out as going from northeast to southwest, 

 namely, Sylvia suecica and fheAlanda alpcHtris. These, and all the oth- 

 ers enmnerated, joined by hosts of X\\<^. more common " million " which 

 aje spread far and wide over the entire northern Paheartic Pegion. 



