MIGRATION. 181 



violence of their impact with the glass condensers 

 of these beacons. Hundreds of all species : 

 woodcocks, snipes, curlews, ducks, finches, crows, 

 owls and so on, hover around till daybreak then 

 make for the shore ; but hundreds remain, either 

 utterly exhausted with their exertions, or killed 

 by concussion. 



If the lighthouses have told us much, the 

 lonely island of Heligoland — an island which 

 is peculiarly well situated for work of this kind 

 — has told us more. The observations from this 

 quarter are by far the most numerous, and the 

 most valuable that have yet been made. These 

 we owe to the late Herr Gatke who spent the 

 greater part of a long and useful life on this 

 circumscribed spot. He studied the movements 

 of the birds as they passed and repassed, as the 

 seasons rolled, with the greatest care and minute- 

 ness. Sometimes they would come to the light- 

 house, as to the lighthouses in other places, in 

 enormous numbers. One night for instance in 

 October, "Goldcrests eddied as thick as flakes 

 in a heavy snowfall ... on the morrow literally 

 swarming on every square foot of the island ; 

 and twelve months later larks in myriads 

 thronged to the bright beams of this same 

 beacon four nights in succession, accompanied 

 by starlings in hardly fewer numbers." 



There is another form of migration, hinted at 

 in the beginning of this chapter, which might 

 almost be described as spasmodic. It is just 

 possible however that it is really periodic, or at 

 least occurs in cycles. 



This is the immigration of vast hordes of birds 



