182 THE BIRDS OF HELIGOLAND 



fail to make its appearance, often in great numbers, directly after 

 its commencement. 



As early as the middle of August, simultaneously with the 

 arrival of the young Chats, the first young Sparrow-Hawks make 

 their appearance. These young birds continue to arrive through- 

 out the whole of September and October, the first old examples 

 not reaching here before the beginning of the latter month ; these 

 old birds, as well as scattered young birds, may still be met with 

 during the whole of November. 



Like all diurnal birds of prey, this species performs its migration 

 journeys during daylight, the birds arriving suddenly as though 

 they had dropped from the clouds, and mostly in large flights, 

 but not until late in the afternoon ; they seem to have travelled a 

 very long distance, for their crops are perfectly empty, while they 

 must be considerably troubled by hunger, if one may judge from 

 the eager manner in which until, and even after, sunset they 

 pursue every small bird which comes within their reach. 



Like most other birds, the Sparrow-Hawk flies during its 

 migration at a very great height, at all events out of the range of 

 vision of the human eye, which may be estimated at least at 6000 

 feet. On one occasion, during an October afternoon, I saw this 

 Hawk arriving in exceptionally large numbers. The sky was covered 

 uniformly with high and somewhat striped white clouds, or rather 

 cirri, which form the most favourable background for perceiving 

 an object at a very great height, when viewed vertically overhead. 

 My attention was attracted upwards by some descending Hawks. 

 Both I and ' Old Oelk,' who was in my company, saw at various 

 heights above us many of these birds descending together in small 

 circles of twos and threes. As their number kept continually in- 

 creasing, we directed our attention to portions of the sky where no 

 birds were to be seen, and observed, after a short and strained look 

 upwards, some scarcely discernible small dark points which, after 

 a short time, we recognised to be Hawks. According to my 

 experience, and that of my companion, the distance at which 

 a bird of the size of a Hawk is still visible as a distinctly per- 

 ceptible point, amounts to about the length of Heligoland i.e. 

 5700 feet; but it is impossible to say how far above this limit 

 the height of the migratory flight of this bird may not have 

 extended. This question of the height at which birds fly during 

 their migration has been discussed more fully in the section on 

 Migration generally. 



Since many of the smaller birds, when pursued by the Sparrow- 

 Hawk, take refuge in the throstle-bush, this bird is also frequently 

 caught in the net, greatly to the joy of the Heligolanders, who 



