OF ISLAND FAUNAS 147 
obtained in the islands, and of these forty-one, or con- 
siderably more than half, are peculiar to the islands, 
not being found elsewhere. Most of those which are 
not peculiar are birds with considerable powers of 
flight, capable of travelling great distances. Of the 
true land birds all but one are peculiar, and this one 
is the common rice-bird (Dolichonyx oryzivorus), which 
occurs throughout the whole of the American continent. 
This bird is markedly migratory, spending its winters 
in the West Indies and Central America, and travelling 
northwards in vast numbers to breed and spend the 
summer in the northern United States and Canada. 
There is, therefore, nothing improbable in the supposi- 
tion that stragglers from the migrating flocks reach 
the Galapagos Islands from time to time, and so pre- 
vent an island type from establishing itself. The other 
land birds of the islands show, as Wallace points out, 
all gradations from close resemblance to forms occurring 
elsewhere to generic difference. Thus the archipelago 
contains a special owl—Asio galapagensis—but this is 
very nearly related to the widely distributed short- 
eared owl (Asio brachyotus). On the other hand, among 
the finches peculiar genera occur, e.g. Geospiza, related 
to genera of restricted range found on the continent 
of South America. Again, though the islands are 
relatively so near together, a peculiar genus may be 
represented by three different species on as many 
different islands. ‘This is well exemplified in the case 
of the honey-creepers of the genus Certhidea, the three 
species of which occur on different islands. 
The reptiles of the islands are especially remarkable. 
The giant tortoises have long been famous, and give 
the islands their Spanish name. Such giant tortoises 
occur only on islands, being found in certain islands in 
K 2 
