Xll PREFACE. 



nests have been carefully studied as to elements of 

 composition and periods of building; and many 

 pairs of the species whose habits' are herein des- 

 cribed, have been closely and diligently watched, 

 with the view of determining the details of incu- 

 bation, and the early history of the young. The 

 various articles which contribute to their main- 

 tenance have been partially derived from repeated 

 observations upon the same species in their 

 natural haunts, and elsewhere; but mainly from 

 examinations of the stomachs of more than seven 

 hundred birds. 



A brief synopsis of the leading items of interest 

 embraced within its scope, cannot be amiss. 

 Herein are found numerous facts which are un- 

 mentioned in the latest American work on birds, 

 besides corroborations of important statements of 

 Audubon and Wilson which have been entirely 

 ignored by its authors. In addition to which, a vast 

 amount of knowledge which has not hitherto been 

 published, and which may be conveniently ar- 

 ranged under the following heads: 



1. Descriptions of nests which show marked 

 deviations from normal structures, and the causes 

 which have probably conduced to the variations. 



2. Labor of nidification whether performed by 

 the male and female separately, or conjointly. 



