252 SIBERIA IN EUROPE. CHAP. xx. 



for that length of time, the wonder is not that so many 

 species of birds have occurred on Heligoland, but that so 

 many have hitherto escaped detection. This must be 

 accounted for on the theory that, after all, the appearance 

 of birds on Heligoland is only accidental. Comparatively 

 little migration is observed by the casual visitor who frequents 

 the Eestaurant to enjoy the oysters and the lobsters, or rows 

 across to Sandy Island to bathe on the shore, and take a 

 constitutional on the " dunes." Now and then a flock of 

 waders may be detected hurrying past ; flocks of pipits occa- 

 sionally land on the island, feed for an hour or two, and then 

 pass on ; and sometimes a scattered and straggling stream, of 

 hooded crows, of heavy and laborious flight, will continue all 

 day long. But by far the most important migration will be 

 found to have taken place " while men slept." Every flock 

 which passes over probably drops a few tired or hungry 

 birds, and a walk through the potato-fields in the morning 

 after a migration night, sometimes turns up the most curious 

 and interesting variety of species which have sought the 

 only cover on the island to feed, or rest, or hide. Perhaps 

 the first bird you flush is a skylark ; the report of your gun 

 starts a golden plover, or a jack snipe ; then you observe 

 some small birds skulking in the potatoes, and you presently 

 secure a little bunting, an aquatic warbler, and a shore-lark. 

 Your next shot may be a corncrake, followed by a ring ousel 

 or a Kichard's pipit. Every night, however, is not a migra- 

 tion night. Sometimes for a week together you may dili- 

 gently tramp the potatoes without finding a bird. Migra- 

 tion is a question of wind and weather. Aeuckens, the 



