136 BRITISH BIRDS. 



In the preceding table will be found a list of the species 

 that occurred at sea in the Mediterranean during the 

 two and-a-half years ; either flying by, flying around, or 

 settling on board the ship. 



It seems that there are three broad routes or zones 

 normally traversed by migrants crossing the Mediter- 

 ranean, somewhat on the lines indicated in Figure VI. 



I. The Gibraltar zone (in which possibly the Balearic 

 Islands may be included, but I have no information 

 about this group). 



III. The Italy-Sicily, Corsica-Sardinia, Malta-Tunis 

 zone. 



V. The Levant zone. 

 This leaves the two large sea-areas (II. and IV.) between 

 the three zones normally untraversed except near the 

 coast-lines, and our " Venus " observations agree with 

 these divisions. 



In II. and IV., abnormal conditions of weather, which, 

 as will be seen, produced such large bird visitations in 

 the other zones, never brought any but a chance bird or 

 two to the ship, indicating clearly that the sea-areas 

 are not normally traversed by, at any rate, those species 

 whose presence in such circumstances may be expected 

 in the other zones, I., III., and V. 



But it is not at all my intention to give the reader the 

 impression that we always fell in with the birds mentioned 

 in the list during the migration seasons, wherever and 

 whenever the ship happened to be cruising in areas I., 

 III. and V. On the contrary, except within a very few 

 miles of the land, no migrating birds of any species 

 (excepting, perhaps, the Pelicans mentioned later on) 

 were ever seen at sea whose presence could not be clearly 

 ascribed to abnormal causes, and even so, their numbers 

 varied inversely as (perhaps the square of) their distance 

 from the land. 



Considering the Port Said district alone, at fifteen 

 miles north of the place, if all the birds that arrived in 

 daylight had travelled across the sea sufficiently low 



