68 NATURAL RESOURCES SURVEY 



(1) the mountains, (2) the plains and "mesas,' 1 an arid 

 steppe type and (3) the valleys; and the plant and animal life 

 follows this distinction very closely. Even the birds that 

 seemingly could so readily pass from one type to another, in 

 the main do not do so but remain quite distinct. In the 

 mountains for instance, are robins and other thrushes, crows, 

 chickadees, nuthatches, canon-towhees, pinonettas, etc. On 

 the steppes are shrikes, sparrowhawks, western quail but 

 especially and vastly outnumbering . all others combined, 

 prairie horned-larks. In the valleys are meadow- larks, 

 Mexican finches, wild geese and ducks, and at least three 

 species of blackbirds and more of sparrows. 



THE PLANT ASSOCIATIONS AND SOCIETIES l 



As the distribution of animals and especially insects is so 

 closely dependant upon that of plants, a study of physio- 

 graphic plant ecology forms a necessary foundation for the 

 study of physiographic animal ecology, but as the author has 

 treated the former in another place ( 2 ), a mere outline of the 

 chief associations and societies to serve as a means of naming 

 those of the animals will suffice here. The names of the 

 plant associations form a most satisfactory nomenclature 

 for animal habitats and one that can be recognized at a glance. 

 No animal, of course, occupies all of the places in its area of 

 distribution so that a mere statement of the latter gives but 

 an imperfect idea of where an animal may be found. You 

 say, for instance, that a certain beetle occurs in New Mexico 

 and Arizona. Yet there would be many places in that terri- 

 tory in which you would search in vain for it. If, however, 

 you stated that it occurs in the Pinus ponderosa formation 

 there, 3 T ou have really told one where to look for it, and- since 

 an animal nearly always occupies all suitable habitats within 

 its area of distribution, you could probably tind it in most 



(1) For the benefit of such of our readers who are not familiar with the terms 

 used in plant ecology it should be explained that an association includes a tract 

 of land dominated over most of its extent by some plant or group of plants that 

 are usually found growing together, as the Yellow Pine, White Oaks, and Wild 

 Gooseberries. An association should cover considerable territory. A society is a 

 subdivision of a formation where some other plant or one only of those composing 

 the formation is locally dominant, such as the Long-leaved Poplar or Red Cedar 

 Societies along streams in the Yellow Pine Formation. 



2) Soon to be published in the Botanical Gazette. 



