THE THROSTLE-BUSHES 199 



question of wind and weather. Aeuckens, the bird-stuffer 

 on Heligoland, told me that birds migrate north-east in 

 spring, and south-west in autumn. Gatke, on the other 

 hand, maintains that the directions are due east and west. 

 Both agree that birds dislike an absolutely favourable 

 or absolutely contrary wind. The former ruffles their 

 feathers and chills them ; the latter, if too strong, impedes 

 their progress. They prefer a side wind, and probably 

 alter their course slightly to accommodate themselves 

 to it. It is even said that they will sometimes tack. 

 Weather is perhaps as important as wind. Under or- 

 dinary circumstances a bird does not require to rest on 

 Heligoland, and the arrivals for the most part are said 

 not to be from any point of the compass, but perpendicu- 

 larly from the sky. The islanders describe with great 

 gusto the sudden arrival of thrushes in this manner. 

 There are scarcely any trees on the island, so the 

 peasants make artificial bushes with a net on one side 

 into which the poor thrushes are driven with sticks and 

 lanterns as soon as they alight. Some hundreds are thus 

 frequently caught in one night. By long experience the 

 Heligolanders know when to expect an arrival of birds. 

 Aeuckens related to me how they would watch on favour- 

 able nights by the throstle-bushes, when on a sudden, 

 without a moment's warning, a rush and whirl of wings 

 would be heard, and the throstle-bush would swarm with 

 thrushes, not dropped, but apparently shot like an arrow 

 from a bow, perpendicularly down from the invisible 

 heights of mid air. It is supposed that migration takes 

 place for the most part at a high elevation, beyond the 

 range of our vision ; that the birds migrate by sight, and 

 not, as has been assumed, by blind instinct ; that they 

 are guided by prominent landmarks with which they have 

 gradually become familiar ; and that many birds which 



