1^6 Allen, Origin and Distribution of N. A. Birds. \ax, x 



Of the 400 essentially Warm Temperate forms only about 6 

 per cent, have a transcontinental range ; about 25 per cent, may 

 be considered as having a more or less general dispersion over the 

 Humid Province, to which they are restricted, and about 44 per 

 cent, range more or less at large over the Arid Province, to which 

 they are practically confined. The remaining 2^ per cent, are of 

 more or less local distribution, part being water birds confined to 

 certain portions of the Atlantic, Pacific or Gulf coasts ; part are 

 more or less maritime land birds, while a few are limited to par- 

 ticular areas of comparatively small extent in the interior, or to a 

 narrow belt along the Pacific coast. As will be noted later, some 

 28 species and 24 subspecies are confined to Lower California 

 and its outlying islands. 



The northern and southern differentiation of the Warm Tem- 

 perate noted above serves, however, as a basis for primary subdi- 

 visions (secondary divisions of the Warm Temperate) of both the 

 Humid and Arid provinces, each being separable into two Sub- 

 provinces (see PI. IV). Thus the Humid Province is divisible 

 into (1) an Appalachian Subprovincc, consisting of the long 

 recognized Alleghanian and Carolinian Faunas, and (2) an 

 Austroriparian Subprovince, consisting of the Louisianian 

 Fauna, as commonlv recognized. The Austroriparian Sub- 

 province is Dr. Merriam's 'Louisianian or Austroriparian sub- 

 region' of his 'Sonoran' region ; the Appalachian Subprovince is 

 the northeastern part of his 'Sonoran,' left by him as an unnamed 

 remainder after setting off and naming as 'subregions' all the 

 other parts of his 'Sonoran Region.' The line separating these 

 two subprovinces marks the southern limit of several northern 

 genera and many northern species, and the northern limit of a 

 still greater number of southern genera and species. 



The Humid Province comprises three fannce, as follows: (1) 

 Alleghanian, (2) Carolinian, (3) Louisianian. These faunae 

 have been so long recognized, and have recently been so well 

 mapped by Dr. Merriam, 1 that a detailed account of them maybe 

 here omitted. 



The Arid Province not only extends, as already stated, from 

 the eastern edge of the Great Plains to the Pacific coast, but also 

 northward over the Saskatchewan Plains, the Plains of the Colum- 



1 N. Am. Fauna, No. 3, map 5. 



