134 BRITISH BIRDS. 



migration passage across the Mediterranean, as are 

 accepted, more or less universally, as rules governing the 

 phenomenon of migration, because it seems to me that 

 not only do spring and autumn passages across the same 

 area differ inter se, but that in many important features 

 each migration area possesses characteristics peculiar 

 to itself. I think, for instance, that the passage across 

 the Mediterranean differs a great deal from that 

 across the North Sea at the same season, while the dis- 

 similarity of the spring and autumn migration in the 

 latter area makes itself sufficiently apparent in all our 

 records. For an explanation of the former we may, 

 perhaps, look to the physical geography, past and present, 

 of the areas under consideration — their climate and their 

 position with reference to the breeding and winter quarters 

 of the migrants themselves. 



During our two-and-a-half years in the Mediterranean, 

 July and February were actually the only months of 

 the year in which the ship never fell in with birds other 

 than regular sea-frequenting species, but for all practical 

 purposes one may say that from mid-December to mid- 

 March, and from mid- June to mid- August, migration 

 over these waters is apparently in abeyance. I say 

 apparently, because in August, if not in July, there must 

 surely be numbers of Limicolce crossing the Mediter- 

 ranean, although not a single representative of that 

 great order ever visited us at sea at any period of the 

 year, an interesting fact which coincides with records 

 from other sources, and doubtless has its own bearing 

 on the mode of passage of this particular group of birds. 



During the rest of the year it was seldom that a cruise, 

 however short, would pass by without our being able 

 to record some migrant visitors to the ship — birds whose 

 presence in such uncongenial surroundings would have 

 seemed strange indeed, had we failed to realise that they 

 were merely the strayed representatives of a feathered 

 concourse travelling between their winter and summer 

 quarters. 



