468 FIELD STUDY IN ORNITHOLOGY. 



wbich emulate the Geoftpisa of the Galapagos. Prof. Newton has shown 

 that while the greater number of those are probably of Anierican origin, 

 yet the South Pucitic has contributed its (juota to this museum oforni- 

 tholOj;ieal rarities, which JNfr. Clarke very justly proposes to make a 

 distincjt biological subregioii. 



That each of the islands of tliis group, how<'ver small, should i)(>s- 

 sess a tlora specifically distinct suggests thoughts of the vast X)eriods 

 occuj>ied in their difterentiation. 



In the Canary Islands, either because they are geologically more 

 recent or because of their proximity to the African coast, which has 

 focilitated frequent immigrations from the continent, the process of 

 ditt'erentiation is only partially accomplished. Yet there is scarcely a 

 resident s[»ecies which is not more or less modified, and this modifica- 

 tion is yet further advanced in the westernmost islands than in those 

 nearest to Africa. In Fuertaventura and Lanzarote, waterless and 

 treeless, there is little change, and the fauna is almost identical with 

 that of the neighbouring Sahara. There is a whinchat, Pratincola 

 dacoiUv^ discovered by my companion, Mr. Meade- Waldo, peculiar to 

 Fuertaventura, which may i>ossibly be fouiul on the opposite coast, 

 though it has not yet been met with by any collectors there. Now, our 

 whinchat is a common winter visitant all down the West African coast, 

 and it seems probable that isolation has i)roduced the very marked 

 characters of the Canaries form, while the continental individuals have 

 been restrained from variation by their frequent association with their 

 migratory relations. A similar cause may explain why the blackbird, 

 an extremely common resident in all the Canary Islands, has not been 

 modified in the least, since many migratory individuals of the same 

 si)ecies sojourn every winter in the islands. Or take the blue titmouse. 

 Our familiar resident is replaced along the coast of North Africa by a 

 representative species. Partis vltra-niarinns^ differentiated chiefiy l)y a 

 black instead of a blue cap and a slate-colored instead of a green back. 

 The titmouse of Lanzarote and Fuertaventura is barely separable from 

 that of Algeria, but is much smaller and paler, probably owing to 

 scarcity of food and a> dry desert climate. Passing 100 miles farther 

 to sea, to Grand Canary, we find in the woods and forests a bird in all 

 respects similar to the Algerian in color and dimensions, with one 

 exception: the greater wing coverts of the Algerian are tipped with 

 white, forming a broad bar when the wing is closed. This, present in 

 the Fuertaventura form, is represented in the Canarian by the faintest 

 white tips, and in the birds from the next islands, Tenerifte and Gomera, 

 this is altogether absent. This form has been recognized as Parns 

 tencriffa\ Proceeding to the northwest outermost island, Palnia, we 

 find a very distinct species, with different proportions, a longer tail, 

 and white abdomen instead of yellow. In the ultinui Thule, Ilierro, 

 we find a second very distinct species, resembling that of Tenerifte in 

 the absence of the wing bar, and in all other respects, except that the 



