CHAPTER X 



SUGGESTIONS AND GUESSES 



SEVERAL important migration phenomena have 

 hardly been touched upon in the previous pages ; 

 a few words about these may not be out of place. 



There is no doubt that now and again American 

 species are met with in Europe, and European in 

 America, though there is no evidence of direct regular 

 trans-Atlantic passage, except from Greenland. The 

 appearance of these birds has been explained in 

 several ways, the general notion being that it is 

 impossible for a bird to fly unaided across the 

 Atlantic, say over 3000 statute miles, without rest. 

 In considering the question we are met with various 

 points on which we still lack knowledge. 



We know that strong-winged waders can ac- 

 complish 2500 miles, apparently without a rest, 

 and that if rest is necessary these birds can swim 

 and rise from the waves. We know, too, that there 

 is regular passage between Greenland and Europe. 

 We do not know how long a bird can, without rest 

 and food, sustain flight ; we do not know the speed 

 it can travel when aided by favourable winds, nor 

 to what extent even passerine birds may rest upon 



119 



