14 MIGRATION. 
at Gibraltar, myself and others distinctly heard Bee-eaters 
passing south at night, and so conclude other birds may do 
the same. 
We have (?;ic?e Andersson's 'Birds of Damara Land/ pp. 18- 
21) an account of the swarms of Hawks which appear there 
at the time they are absent from Europe and North Africa; so it 
may be reasonably inferred with regard to one species, Milvus 
korschun (the Black Kite), that some of the vast numbers 
which pass the Straits of Gibraltar retire in autumn through 
the tropics to South Africa. 
The best site for watching the departure of the vernal mi- 
gration is at Tangier, where just outside the town the well- 
known plain called the Marshan, a high piece of ground that 
in England would be called a common seems to be the 
starting-point of half the small birds that visit Europe. 
Both the vernal and autumnal migrations are generally 
executed during an easterly wind, or Levanter : at one time I 
thought that this was essential to the passage ; but it appears 
not to be the case, as whether it be an east or west wind, if it 
be the time for migration, birds will pass, though they linger 
longer on the African coast before starting if the wind be 
westerly; and all the very large flights of Raptores (Kites, 
Neophrons, Honey-Buzzards, &c.) which I have seen passed 
with a Levanter. After observing the passage for five springs 
I am unable to come to any decided opinion, the truth being 
that as an east wind is the prevalent one, the idea has been 
started that migration always takes place during that wind. 
Nevertheless it is an undoubted fact that during the autumnal 
or southern migration of the Quail in September, they collect 
in vast numbers on the European side, if there be a west 
wind, and seem not to be able to pass until it changes to the 
east ; this is so much the case that, if the wind keeps in that 
quarter during the migration, none hardly are to be seen. 
On some occasions the passage of the larger birds of prey 
is a most wonderful sight ; but of all the remarkable flights 
of any single species, that of the common Crane has been the 
most noteworthy that has come under my own observation. 
On the Andalucian side the number of birds seen even bv 
