UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 12, No. 4, pp. 51-294, pis. 3-13, 9 text figs. March 20, 1914 



AN ACCOUNT OF THE MAMMALS AND BIRDS 

 OF THE LOWER COLORADO VALLEY 



WITH ESPECIAL REFERENCE TO THE DISTRIBUTIONAL 

 PROBLEMS PRESENTED 



BY 



JOSEPH GRINNELL 

 (Contribution from the Museum of Vertebrate Zoology of the University of California) 



CONTENTS 



PAGE 



Introduction 51 



Itinerary 53 



Description of the Colorado River 57 



Zonal and faunal position of the region 62 



The associational areas of the region 66 



The Colorado River as a highway of dispersal and center of differentiation 



of species 97 



The Colorado River as a hindrance to the dispersal of species 100 



The problem of barriers with regard to birds and mammals 107 



Check-list of the birds 110 



General accounts of the birds: local distribution, migration, variation, molt. 



habits 113 



Check-list of the mammals 217 



General accounts of the mammals: local distribution, variation, habits 218 



Literature cited 269 



INTRODUCTION 



The southeastern frontier of California lies in the heart of a vast 

 desert region possessing a fauna and flora of notable variety and 

 peculiar specialization of forms. Cutting through the center of this 

 desert area flows the great Colorado River. Politically, this river 



