MIGRATION 163 



the same bird to the same breeding place in successive 

 years. A swallow marked in Aberdeenshire in 19 12 returned 

 to the same farmsteading the following year. A swift 

 " ringed " in Ayrshire in 19 14 was recaptured in the same 

 place in 19 18, having doubtless been to Africa four times 

 in the interval. The same regularity of return to the 

 original homestead has been proved in the case of some 

 other birds, such as the stork. 



§ 2. Problems in Process of Solution 



(a) Routes, — More facts must be collected before 

 much can be safely said in regard to the migratory routes. 

 The most useful data are those furnished by observers at 

 lighthouses, lightships, and strategic inland stations, and 

 by the " ringing " method. In " ringing " birds a very 

 light aluminium ring of appropriate size, bearing a stamped 

 number and address, is fastened to the instep region of the 

 foot. A small percentage of these birds are afterwards 

 heard of from distant parts, and if the rings are returned to 

 the marking station with information as to the date and 

 place of the bird's recapture, there is gradually built up a 

 knowledge of the paths that are followed in migration. 

 Thus rings put on storks in North Germany have been 

 returned from Damascus, Alexandria, the Blue Nile, 

 Rhodesia, the Kalahari desert, Basutoland, and elsewhere, 

 so that Dr. Thienemann was able to conclude definitely that 

 there is an autumnal migration of storks from the shores 

 of the Baltic to South Africa. 



"In the same way it has been made clear that there is 

 among hooded crows, for instance, a great westward move- 

 ment in autumn, e.g. from Finland along the shores of the 

 Baltic, and that there is a subsequent curve towards the 

 south. This westward and then southward curve seems to 

 be true of many birds in North Europe. Certain contingents 

 seem to swerve southwards by the valleys of the Rhine and 

 the Rhone, and then across the Mediterranean to North 

 Africa. Other contingents seem to go further westwards. 



