6000 species are already ascertained," and many new species
are added every'year to the catalogue. The whole number
in existence müst be very much greater than this aggregate,
since 500 species havé been ascertained in the'colony ó f thé
Cape,* while the ornithology of most intertropical countries)
which abound in tribes of birds* has been, in comparison)
little explored. Europe and the United States are, perhaps)
the only regions the winged tribes of which have been adequately
compared. The known birds of the new world were
reckoned by Charles Lucian Bonaparte, in 1827, to be three
hundred and ninety-six'species, of which three hundred and
èighty-two belong to the United States. The number of species
ascertained in Europe in 1832, was stated by the author
of an excellent paper in the Quarterly Review, to three
hundred and ninety-five, of which two hundred and seventy-
seven species are natives of Britain and Ireland. The speciés
of Europe and of North America have beén» classed under
one hundred and seven genera, of which sixty-four are common
to both continents.
Of all existing tribes of animals, birds and thè'Cetacea
are, partly owing to their structure, and in part by the nature
of the media they inhabit, best fitted for extensive migration.
Accordingly in these tribes, and scarcèly in arfy others,itKÉ-ë’
are individual species which appear to be almost universally
spread. The locomotive powers of some birds are so great,
that scarcely any natural barriers are capable p f setting
limits to their migration. The only boundaries which confine
them are uncongenial climates, or physical circumstances incompatible
with their existence. Some of the largest birdf
of prey are found in many distant countries. It has been
observed, that even those tribes which are nearly or wholly
destitute of the power of flight, are more extensively spread
than the wingless animals: that the ostrich, for example, is
to be found over all Africa, from the Cape of Good Hope to
the-Cyrenaik, and from Cape Verde to Babel-mandeb ; that
the same osprey, or Fishing Eagle, wanders along, the shores
• South African Quarterly Journal, No. 1. p. 10.—Quarterly-Review, vol. 47,
p. 853.
of Scotland, and on those of the south of Europe and of New
Holland. The Chinese goshawk is said to reach from the
south-eastern tracts, of Asia to. the western coast of Europe,
inhabiting many intermediate stations and extending across
the broad expanse of the American continent: the Lammer-
geyer haunts the heights of the Pyrenean, the mountains of
Abyssinia, and the Mongolian steppes. The Penguin Falcon
occurs in Greenland, Europe, America,^and New Holland.*
The structure, of these tribes, or the local circumstances of
the countries where they were placed, affords a full and adequate
explanation of the fact that their wanderings have been
so extensive. On the other hand it appears as a general observation,
that tribes in respect to which these conditions are
found to be reversed, are confined to a very limited range.
This is the case especially with birds inhabiting islands and
endowed with but weak powers of flight. An example may
be found in the species befon^iirg to the parrot tribe, ©f which
the number knowmsome years ago amounted-to two hundred
and thirty-nine. These are divided .into groupes, which are
distributed separately to different parts of the world, to India,
to Afriea, and to America. The Lories inhabit New Guinea,
Moluccas, and other eastern islands, but are unknown to the
new world. Owing to the weakness of their flight, one island
of an. archipelago often contains a peculiar species which %
wanting-in otherislands of the same groupe.f Another ik
lustration off the same remark is furnished, as Mr. Lyell has
observed, by the humming-birds. They are peculiar to the
New World, where a few have a wide ran g e; Trochilus Flam-
mifrons is,;common to Lima, Juan Fernandez and the Magel-
lanik, but other species are peculiar to one of the West
India islands.!. The common grouse peculiar to Britain is a
similar instance of siqglé collocation.
It maybe remarked, that the distribution of genera among
birds to different countries) displays the same method of ar-
* Quarterly Review, vol. xlvii. p. 357r
+ Remarks on the History and’Distribution' of the Genus Psittacus, or Parrot.__.
Edin. Philo. Magazine, May, 1832.
$ Principles of Geology, vol. ii.