BIRD BEHAVIOUR 



494 lilKU bLHAVlUUK XVII. 4- 



whereas older individuals return to their old nesting sites. Individual 

 memory therefore plays a part. The birds often migrate singly and 



Fig. 302. Direction of migration of the stork (Ciconia). The black spots represent points 



of recovery of birds ringed in Germany. The dotted areas show the pathways produced 



by ecological and geographical factors. (After Schulz and Stresemann.) 



experiments in a planetarium have shown that warblers turn accurately 

 in the appropriate direction as given by the stars. 



The available evidence therefore suggests (a) that for most species 

 at least there is a preferred direction for migration, which is indepen- 

 dent of experience. Hand-reared warblers will orient correctly by the 

 stars without previous experience; (b) that they may be deviated by 

 features of the environment such as coastlines or hills; (c) that after 



