INTRODUCTORY. XI 



word. They are characterized by a paUor of plumage, the direct result 

 of the low annual rain -fall, in accordance with now generally recognized 

 laws which have been ably elucidated by Allen, Baird, and others. 



There only remains the grateful duty of recording here an acknowl- 

 edgment of favors received in the preparation of this work. My 

 pleasure might have been increased by mention of various other names, 

 had not the circumstances under which the book has been written de- 

 prived me in great measure of the desired and freely offered cooperation 

 of several kind friends. I am particularly indebted to Mr. T. M. Trippe, 

 of Colorado, for a valuable paper on the birds of that Territory, which 

 I have incorporated with my pages. My thanks are likewise due to Mr. 

 J. A. Allen for various interesting communications based upon his 

 original observations in different parts of the West ; to Mr. J. Steven- 

 sou, to whose collections I have frequent occasion to allude ; and to Mr. 

 T. G. Gentry and Dr. J. M. Wheaton. In the labor of compiling syn- 

 onymy I have been materially assisted by some manuscript records of 

 (juotations which Professor Baird very kindly placed at my service. 



1 cannot close this communication without an expression of the obli- 

 gation under which other ornithologists beside myself rest to you for 

 the very material services you have rendered to Ornithology — both by 

 your successful personal labors and by your able direction of other means 

 at vour command — services the more commendable in the fact that thev 

 have been gratuitously rendered apart from your own special lines of 

 scientific inquiry. I do not hesitate to say that no one, not an ornithol- 

 ogist, has contributed more to the advance of our knowledge of the 

 birds of the West. 



I am, Sir, &c., 



ELLIOTT COUES. 



Dr. F. V. Hayden, 



U. 8. Geologist, <jDc., etc., ttc, 



In charge Geological Survey of the Territories, 



Washington, D. G. 



