KF.roirr on iiii; .Mi(a;.\TiON of iuIx-ds. .H>!1) 



importance for the (Ictciiiiiuiition of tlu' nii.^iMlioii routes, l-'xteinal 

 circurastanccs forbid us to uotice all these works here, althouuh they 

 may be worth it, like those of Radde. I'leske, Olph-dalliard, Oustalet, 

 Uresser, aud others, aii<l notwithstan<liuj;- they coutaiu mauy sin}j;le re- 

 sults, many ^'aluabh' thou,i>lits on bird ]ni<>Tation. 



On the other hand, it seems proper to here call attention to some 

 special investigfations on bird migration in certain i-ejjions, founded on 

 avifauna! materiak 



Some i)laces have lon^' been known in the western portion of our 

 eontinent where miiirating- birds collect in crow^ds because obstacles 

 situated on the side, like seas, allow a passage here only; or, like 

 mountain regions, only here leave the door open. Such highways have 

 l)een examined farther eastward in regions which are impoitant for the 

 migration between great districts. 



From his comprehensive observations in the years lS.')7-79 in the 

 Aral-Thian-Shan region, X. Severtzow has given us (BnlL dcs Nat. Moh- 

 coir, 1.S80,) a very brief view of the highways where the greatest 

 numbers of birds of ])assage eongregate. lie designates cartograph- 

 ically three gTou])s of such routes: A, through the Kirgheez steppes, 

 from the river Tral to the Sir, characterized by the enormous number 

 of merely passing birds; B, along the western border of the Thian- 

 Shan mountains, distinguished l)y a tolerably large migration, and by 

 the circumstance that the nati\ e summer birds give way to winter 

 guests: and C, through the interior ])ortions of the range mentioned, 

 known chiefly by the annual change of species Just alluded to. The 

 wintering on the routes P> and (' is owing to the warm s])rings existing 

 there. 



Severtzow mentions fuithcr the coniie<'tion of the i-outes nami^l 

 with th(^ kiu)wu migration routes along the Irtish ami the Ol) on the 

 one side; on the other with their pi'esumptive continuations in T'ersia, 

 Afghanistan, IMiuJal). and in tlie region of the Indus, lie designates 

 tin- Altai as a region whence tlu' migration rcuitcs diverge: in the 

 southwest towaid llussian Turkestan: in the south towards the des- 

 ert; and in the southeast towards Ohhia. The movement of the birds 

 of ])ass;ige in a vertical direction from the highland of Thian-Shan 

 and i*ameer towar<ls the low grounds is :ilso suggested l)y him. 



Ivcferring to the details to be s])ecified later, Severtzow here com- 

 nuiincates sojue general jtoints of view (pp. 282-284). The course of 

 the stepi)e routes depends on the existence and situation of the waters 

 in them. On the other hand, the general extent of the lofty Thian- 

 Shan range compels the flocks moviDg: at a short <listance from it to 

 follow a general direction from <'ast northeast to west southwest; 

 therefore, great masses of birds of passage are |»ressed together on 

 the western border of the range (Tschemkeud-Tashkend), while these 

 juasses can si)read out again to the northward, as also to the south- 

 ward. 



