20 DISPERSAL AND MIGRATION. [PART 1. 
of April, however cold it may be, while its departure may take 
place from the end of September to late in October, and is said by 
Forster to occur on the first N. or N.E. wind after the 20th of 
September. | 
Almost all the migratory birds of Europe go southward to 
the Mediterranean, move along its coasts east or west, and cross 
over in three places only ; either from the south of Spain, in the 
neighbourhood of Gibraltar, from Sicily over Malta, or to the 
east by Greece and Cyprus. They are thus always in sight of 
land. The passage of most small birds (and many of the larger 
ones too) takes place at night; and they only cross the Mediter- 
ranean when the wind is steady from near the east or west, 
and when there is moonlight. 
It is a curious fact, but one that seems to be well authenti- 
cated, that the males often leave before the females, and both 
before the young birds, which in considerable numbers migrate 
later and alone. These latter, however, seldom go so far as the 
old ones; and numbers of young birds do not cross the Mediter- 
ranean, but stay in the south of Europe. The same rule applies 
to the northward migration; the young birds stopping short 
of the extreme arctic regions, to which the old birds migrate. 
When old and young go together, however, the old birds take 
the lead. In the south of Europe few of the migratory birds 
stay to breed, but pass on to more temperate zones; thus, in the 
south of France, out of 350 species only 60 breed there. The 
same species is often sedentary in one part of Europe and migra- 
tory in another; thus, the chaffinch is a constant resident in 
England, Germany, and the middle of France; but a migrant in 
the south of France and in Holland: the rook visits the south 
of France in winter only: the Falco tinnunculus is both a 
resident and a migrant in the south ot France, according to 
M. Marcel de Serres, there being two regular passages every 
year, while a certain number always remain. 
1 Marcel de Serres states this as a general fact for wading and swimming 
birds. He says that the old birds arrive in the extreme north almost alone, 
the young remaining on the shores of the Baltic, or on the Jakes of Austria, 
Hungary, and Russia. See his prize essay, Des Causes des Migrations, &c. 
2nd ed., Paris, 1845, p. 121. 
