KHTOKT ON rilK .MKJKATlUX oF r.lKl)S. ,'V.>.') 



writer will by ii<» iiicaiis pass oW liis oljjcctioiis as critically \vei,i;lie(l 

 refutations. 



These coiitiiieutsil ways appear to iiic in a i^reat part very (loubtfiil. 

 The routes from west to east esjx'cially aie of an enormous length, 

 like that from the Dwiua to South China, lead entirely through the 

 interior of a continent, without the guichMicc of a homogeneous well 

 characterized conformation of soil, and touch alternately great forest, 

 desert, and mountain regions. It is ditticult to conceive how birds of 

 passage could liiul their way (ui this route. It seems much more prob- 

 al)le that we know too little Just now about the occurrence of the species 

 examined, some of which are difficult to distinguish, and that their 

 winter stations are eventually to be sought nnu-h nearer, at the most 

 in the regions whither Severtzow's routes lead. In the meantime, I 

 will not venture upon a scientific Judgment in this respect until the 

 author submits the facts on which his opinions are based. 



After this short statement of the developiueut of the question of the 

 migration of birds, the writer takes the liberty to cast a retrospective 

 view upon it. Tn the study of the migration of birds, two kinds of 

 material for investigation present themselves — the avi ])hen<)logical and 

 the avi-faunal observations. Since the hrst-named were collected for 

 this very purpose, it was at hrst thought that the investigation should 

 be commenced on this side. The avi-phenoh»gical material explains 

 the times of migration, and from these results an attempt was made to 

 infer the directions of the migration. Nevertheless these results a]t- 

 peared too inexact to serve as a starting point for further investiga- 

 tions. An attem])t was therefore made to take the op])osite course, 

 first to fix the migration routes from the avi-faunal material, and after- 

 ward to emi)loy the method Just mentioned with reganl to the times of 

 migration. 



An attem])t to fix geographically the routes (►f souu' spe<*ies of birds 

 l»roved that the (luestion could be advanced in this way. Tlie need 

 for more abundant material now made itself felt, and new observations 

 were zealously collected year after year in difiereut countries. 



It must be coiuicded that at present very considerable energy is 

 devoted to the investigation of the distribution of birds and of the 

 secrets of their migration. The annual reports, which contain obser- 

 vations from numerous stations, are nudtii)]ying. This gratifying 

 increase in the material of facts which are to extend and deepen our 

 knowledge of migration, is characteristic of the ornithological in(piiry 

 of the past years. It is to be desired that these efibrts may continue 

 and may be further completed, and that in conse(|uence the (piantity 

 of material shall go on increasing. Nevertheless the coiulitiou of af- 

 fairs may also examined and judged from another side. 



In such investigations the quantity of observations will certainly 

 not aloiu' decide the (piestion. The material is also to be treated 

 scientifically. The inner coniu'ction of the facts and their litness to 



