94 
INTRODUCTION. 
owl families, which prey upon the stragglers. Not 
is this similarity between the birds of the two con- 
tinents confined only to such as inhabit the land. 
It is a curious and unrecorded fact, that a migra- 
tion almost equally extensive takes place among the 
waders and swimmers. During many years resi- 
dence, for instance, in the island of Sicily, a spot 
peculiarly favourable for carrying on observations 
of this nature, we never met with the purple or the 
night herons, or the glossy ibis, except during the 
spring or autumnal migrations ; at such times the 
whole island may be considered like a vast preserve 
of quails, and numerous other migratory birds. In 
respect to the small soft-billed or fly-catching species, 
forming part of the fly-catcher and warbler families, 
little can be said beyond the fact that their route is 
southward, after leaving our hedges and woods in 
the autumn. They do not appear to take Italy or 
Sicily in their way, which, if they ventured on the 
shores of Northern Africa, it is more than probable 
they would do, seeing that the configuration of those 
countries renders them resting places, as it were, 
for such feeble winged birds before they ventured 
to cross the Mediterranean. Northern Africa is 
certainly the boundary of the African bush-shrikes 
(Mahconotus ) ; one species, the beautiful M. bar- 
barus, seems the most northern visitor, while its 
southern range extends to Senegal. There must 
he many birds peculiar to sandy deserts in the arid 
tracks of Barbary, Algiers, &c. which would find 
no congenial locality on the fertile shores of the 
