BTRODUCTION 



This is the sixth in a scries of bulletins of the United States 

 National Museum on the life histories of North American birds. 

 Previous numbers have been issued as follows: 



107. Life Histories of North American Diving Birds, 1919. 



113. Life Histories of North American Gulls and Terns, 1921. 



121. Life Histories of North American Petrels, Pelicans, and 

 their AlHes, 1922. 



126. Life Histories of North American Wildfowl, 1923. 



130. Life Histories of North American Wildfowl, 1925. 

 The same general plan has been followed, as fully explained in 

 Bulletin 107, and the same sources of information have been utilized. 

 The classification and nomenclature adopted by the American 

 Ornithologists' Union, in its latest check list and its supplements, 

 have been followed, mainly, with such few changes as, in the author's 

 opinion, will be, or should be, made to bring the work up to date and 

 in line with recent advances in the science. 



The main ranges are as accurately outlined as limited space will 

 permit; the normal migrations are given in sufficient detail to indi- 

 cate the usual movements of the species; no attempt has been made 

 to give all records, for economy in space, and no pretence at com- 

 plete perfection is claimed. Many published records, often repeated, 

 have been investigated and discarded; many apparently doubtful 

 records have been verified; some published records, impossible to 

 either verify or disprove, have been accepted if the evidence seemed 

 to warrant it. 



The egg dates are the condensed results of a mass of records taken 

 from the data in a large number of the best egg collections in the 

 country, as well as from contributed field notes and from a few pub- 

 lished sources. They indicate the dates on which eggs have been 

 actually found in various parts of the country, showing the earliest 

 and latest dates and the limits between which half the dates fall, the 

 height of the season. 



The plumages are described only in enough detail to enable the 

 reader to trace the sequence of molts and plumages from birth to 

 maturity and to recognize the birds in the different stages and at the 



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