148 BRITISH BIRDS. 



flies (locally called typhoon flies), and the sea is sometimes 

 strewn with their corpses. The upper strata of the 

 atmosphere, judging from the actions of Swifts, Black- 

 headed Gulls and many other species of birds, must 

 frequently be full of insects. Diptera and other insects 

 often appear on board a ship at sea, and I hazard the 

 suggestion that insectivorous birds, especially those 

 species that habitually take their food on the wing, may 

 perhaps be able to obtain sufficient fuel for their loco- 

 motion to enable them to make considerably longer 

 migratory flights than are generally attributed to them. 



Rather opposed to this suggestion is the fact that it is 

 the exception to find anything contained in the stomachs 

 of birds taken on passage, but it must be remembered 

 that digestion is very rapid. 



Another occurrence of some interest, which may be 

 put down to the influence of rain on migration, was as 

 follows : — 



On September 8th, 1907, the "Venus" was about 

 fifteen miles to the south-westward of the Dardanelles. 

 During the previous night it had been blowing hard from 

 north-east to north-north-east in the Sea of Marmora 

 and iEgean Sea, accompanied by heavy showers. The 

 wind was still very fresh from the same direction, when, 

 at 11 a.m., a party of migrants, amongst which were 

 recognised House-Martins, Swallows and a Nightingale, 

 flew by the ship, hugging the surface of the water, going 

 about north, that is with the wind two points on the bow, 

 progressing, of course, very slowly. 



Later in the day another Hirundo, doing the same, 

 was seen in the distance. 



The points about this that seemed remarkable were : — 



(1) The birds were flying north instead of south. 



(2) They were not flying in the best direction to make 

 the land, which they were presumably trying to do. 



The latter points to the fact that they had quite lost 

 their bearings ; their position, coupled with the time of 

 day, which does not fit in with the time of departure as 



