42 



MIGEATION. 



enjoying the summer sun on the mud-flats of Durban Bay, probably migrate to breed on 

 the tundras around Archangel. 



Migration of 



Passerine 



birds. 



It must not be supposed that the greater proportion of birds migrating across Heli- 

 goland are water-birds ; on the contrary, the species which appear in the greatest numbers 

 are small Passerine birds who, presumably possessing weaker powers of flight, are most 

 anxious to find a temporary rest on such adventurous journeys. The following notes from 

 Gatke's diary are most interesting : — 



