THE BIRDS OF HELIGOLAND 239 



The migration of the Song Thrush commences in the spring, 

 according to the state of the weather. As early as the beginning 

 of Marcli, or even earlier — I find it noted at odd places in my 

 journal as early as the third week in February — this migration 

 contiimes incessantly until the middle of May. The return migra- 

 tion begins in the middle of September and lasts until the end of 

 October or middle of November. A light south-east and south- 

 south-east is the most favourable wind for both migi-ation periods, 

 especially if it be accompanied by tine warm weather. Besides 

 these regular flocks of migrants, there appear here almost annually, 

 during the first days of July, small comjjanies of from five to six 

 j-oung birds. These often have theii' upper parts still marked with 

 light spots. They frequent chiefly dense bushes and shrubberies 

 in gardens. 



The only conclusion to be drawn from the early appearance of 

 birds like these is that they must have been bred on Heligoland. 

 If so, it remains to be explained where their nest could have been 

 situated, unless, perhaps, in some dark cleft of the rocks, since 

 bushes dense enough to serve as the nesting place of a Thrush are 

 not to be found on the island. 



The arrival of the Thrushes in the quiet dawn of morning is 

 marked by a peculiar buzzing sound, the birds shooting down from 

 a great height with a rapidity much greater than that of a sky- 

 rocket, and mostly in one steep, perpendicular line of descent ; 

 sometimes, however, they describe a two- or three-fold zigzag, as 

 one may recognise from the changing tone of the noise. The 

 downrush of a Thrush, Pigeon, or Snijje, is far too rapid to be 

 capable of observation by the eye ; one is only able to see it at the 

 last moment, in which the bird suddenly approaches the ground 

 and forthwith settles thereon. This takes place sometimes in a 

 slightly inclined direction, sometimes almost perpendicularly. 



Such a sudden and steep descent, however, takes place only in 

 calm, clear weather ; if the atmosphere is damp, dull, and heavy, 

 the birds arrive flying at a lower elevation. 



During a strong migration the Thrushes buzz about at early 

 dawn with the speed of an arrow through the streets, among 

 scattered houses and gardens, and, in this way, precipitate them- 

 selves into the throstle-bush or other shrubs. The greatest speed 

 at which the birds fly during the day is not to be compared with 

 that of their flight during these early hours. The latter probably 

 represents the last spurt at the close of the migratory journey, and, 

 in the case of the spring migration of the Red-spotted Bluethroat, 

 reaches the astonishing result of one hundred and eighty miles per 

 hour. 



