VIII INTRODUCTION. 
. The following have contributed photographs: American Museum . 
of Natural History, R. M. Anderson, Bird-Lore, W. 8. Brooks, E. S. 
Cameron, The Condor, W. L, Dawson, D. R. Dickey, W. E. Ekblaw, — 
W. L. Finley, Francis Harper, H. K. Job, Lynds Jones, F. E. Klein- r 
schmidt, D. B. MacMillan, C. F. Stone, J. E. Thayer, C. H. Towns- 
end, 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 Bio- 
logical Survey, the California Academy of Sciences, the Museum of 
Comparative Zoology, the United States National Museum, the Uni- 
versity of California, and the private collections of Louis B. Bishop, 
William Brewster, Jonathan Dwight, and John E, Thayer. Speci- | 
mens 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 lament- 
ably insufficient in many cases to arrive at entirely satisfactory con- 
clusions. di 
Mr. Charles E. Doe has kindly loaned us an egg of the whiskered 
auklet, and Col. John E. Thayer an egg of the Kittlitz’s murrelet for _ 
use in making the illustrations. . 
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 distriby- 
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