13 



nated, because each zone shows differences hypsometrically greater 

 or less, by which the uniformity of the data is influenced. 



A further development of this method is furnished by the 

 maps, the drawing of which was initiated by J. SCHENK on the basis 

 of the foresters' observations. Each of these maps (Tab. X. A and 1 5.) 

 shows the spreading of one species of birds during the colonisation 

 of a certain area in spring, at the same time characterising the 

 distribution of this species. The limits correspond with A. v. MIDDEN- 

 DORFF'S isepipteses, as schematised by this enquirer on his maps. 



The progression of the spreading in spring: 

 Tab. X. 1. of the Chimney Swallow: S. N. 

 2. of the Wagtail W. E. 

 3. of the Cuckoo S. E. N. W. 

 4. of the Stork S. E. N.W. 

 5. of the Woodcock S. W. N. E. 



As clearly proved in the course of this sketch of our method, 

 a progressive deepening of our knowledge of bird migration is 

 evident and puts Hungary certainly at the head of all countries 

 where such observations are made, furthermore, it is apparent, that 

 in such a way many a ,,puzzle" might be solved and many ,,marvels" 

 might be explained in a perfectly natural way; but, on the other 

 hand, it is equally manifest that the phenomenon of migration in 

 its progress can only be recognised on the basis of interzonally 

 organised cooperation. 



Without any knowledge of the wintering places of our birds 

 of migration, without sufficient knowledge of all the areas of the 

 palaearctic and arctic zone in their mutual relations, the result of 

 even the best-worked area will always remain a mere fragment, 

 at the best only a hint. 



If, however, we succeed in prevailing on at least the European 

 railway-stations to observe the migration of the chimney-swallow 

 as was done in Hungary in 1898, we shall be on the eve of solution. 



