546 
GEOGRAPHICAL ZOOLOGY. 
[part IV. 
always to a great extent limited their range. Yet these harriers 
have not been absolute ; and in the course of ages birds have 
been able to reach almost every habitable land upon the globe. 
Hence have arisen some of the most curious and interesting 
phenomena of distribution ; and many islands, which are entirely 
destitute of mammalia, or possess a very few species, abound in 
birds, often of peculiar types and remarkable for some unusual 
character or habit. Striking examples of such interesting bird- 
faunas are those of Hew Zealand, the Sandwich Islands, the 
Galapagos, the Mascarene Islands, the Moluccas, and the An- 
tilles; while even small and remote islets, — such as Juan Fer- 
nandez and Norfolk Island, have more light thrown upon their 
past history by means of their birds, than by any other portion 
of their scanty fauna. 
Another peculiar feature in the distribution of this class is 
the extraordinary manner in which certain groups and certain 
external characteristics, have become developed in islands, 
where the smaller and less powerful birds have been pro- 
tected from the incursions of mammalian enemies, and where 
rapacious birds — which seem to some degree dependent on the 
abundance of mammalia — are also scarce. Thus, we have the 
Pigeons and the Parrots most wonderfully developed in the 
Australian region, which is pre-eminently insular; and both 
these groups here acquire conspicuous colours very unusual, or 
altogether absent, elsewdiere. Similar colours (black and red) 
appear, in the same two groups, in the distant Mascarene islands ; 
while in the Antilles the parrots have often white heads, a 
character not found in the allied species on the South American 
continent. Crests, too, are largely developed, in both these 
groups, in the Australian region only ; and a crested parrot for- 
merly lived in Mauritius, — a coincidence too much like that of 
the colours as above noted, to be considered accidental.' 
Again, birds exhibit to us a remarkable contrast as regards 
the oceanic islands of tropical and temperate latitudes; for 
while most of the former present hardly any cases of specific 
identity with the birds of adjacent continents, the latter often 
show hardly any differences. The Galapagos and Madagascar 
