Vlll INTRODUCTION 



F. E. Kleinschmidt, D. B. MacMillan, C. F. Stone, J. E. Thayer, 

 C. H. Townsend, and Alex. Walker. All such photographs which 

 have been used have been marked with the name of the photographer. 



In the study of molts and plumages free access has been given to 

 the collections of the American Museum of Natural History, the 

 Biological Survey, the California Academy of Sciences, the Museum 

 of Comparative Zoology, the United States National Museum, the 

 University of California, and the private collections of Louis B. 

 Bishop, William Brewster, Jonathan Dwight, and John E. Thayer. 

 Specimens for study have also been loaned by Louis B. Bishop, 

 William L. Finley, the Geological Survey of Canada, F. Seymour 

 Hersey, Lawrence M. Huey, and P. A. Taverner. The conclusions 

 arrived at regarding molts and plumages are based on a careful study 

 of all this material, but even that great mass of material proved 

 lamentably insufficient in many cases to arrive at entirely satisfac- 

 tory conclusions. 



We are also indebted to the officials of the following institutions 

 for a mass of data, taken from specimens in their collections, which 

 has been useful in working out distributions and migrations: Bio- 

 logical Survey, California Academy of Sciences, Carnegie Museum, 

 Colorado Museum of Natural History, Geological Survey of Canada, 

 United States National Museum, and University of California. 



With the consent of the American Museum of Natural History and 

 Mr. Donald B. MacMillan, Mr. W. Elmer Ekblaw has sent us a full 

 report of the ornithological results of the Crocker Land expedition. 

 This generous contribution has enabled us to publish much new and 

 interesting information regarding arctic bird life in advance of their 

 own plans for future publication. For this exceptional courtesy my 

 readers and I are very grateful. Furthermore, the American Mu- 

 seum of Natural History has kindly placed at our disposal the entire 

 collection of bird photographs made by members of this expedition, 

 from which we have selected what we wanted to use. I am therefore 

 indebted to them for the use of all photographs taken by Mr. Mac- 

 Millan and Mr. Ekblaw. 



Much of the merit in the work is due to the untiring efforts of 

 the author's valued assistant, Mr. F. Seymour Hersey, who has spent 

 many months in the field, often in remote localities, gathering speci- 

 mens, photographs, and notes for use in this work. The distribu- 

 tional part of the work was practically all done by him, with what 

 assistance Doctor Bishop and the author could give him. No one 

 who has not done work of this kind can appreciate the mass of detail 

 to be handled and the expert knowledge necessary to handle it 

 properly. 



Finally, thanks are due to the author's devoted wife, Madeleine 

 V. Bent, for many weary hours of painstaking work in typewriting, 



