1 82 Field and Forest Rambles. 



sparrow of the island), so closely allied to the Italian spar- 

 row, which is found in Sicily and Calabria, as to lead to the 

 belief that there is here again a communication between these 

 very distinct" forms * Would space allow, we might multiply 

 examples similar to the above. Suffice it to say that, con- 

 sidering the close and intimate connection between many 

 species, and the influence of migrations in bringing about an 

 intercourse between closely allied forms, it may be readily 

 believed that there is no branch of natural history more likely 

 to aid our knowledge of the causes of variations in animals than 

 that which aims at establishing their geographical limits and 

 movements. 



Having briefly indicated the chief points in connection with 

 the migrations of the North American birds, I shall epitomize 

 a few facts regarding their distribution. The most important 

 of which is the effect of certain, influences on the size and 

 external appearance of species. It has been found, from vast 

 collections of specimens from remote localities, that there are 

 not only pronounced differences in size, but also in coloration, 

 between animals of the same species from high and low latitudes ; 

 morever, that these differences are apparent in individuals of 

 the same species, having a wide distribution in the same 

 latitude, and even as regards elevation above the sea level. 

 In birds these peculiarities are not so apparent as in man and 

 the quadrupeds ; however, several remarkable instances might 

 be adduced among migratory and non-migratory birds. With 

 reference to these it has been observed that migratory birds 

 remarkable for their great range show the leastvariation in size, 

 whereas such as have a wide distribution in latitude without any 

 special migration present very pronounced discrepancies in the 

 development of certain organs, such as the wings, bill, feet, 

 etc. ; indeed, so marked are these in individual species of 

 woodpeckers, that it has been the impression of some 

 naturalists that the extremes, from widely remote localities, 

 * Author, op. cit., p. 85. 



