INTRODUCTION. 



I^HE present edition of this work is greatly enlarged and improved, 

 and the effort has been made to have it include all that is known 

 regarding the nesting of all species of North American Birds. 



Oology has made rapid strides during the last lew years, and eggs 

 of birds which were almost unknown a few years ago are now com- 

 paratively common. This is principally due to the greater number of 

 collectors in the field, and to the intelligent efforts that have been 

 made to secure the eggs of those that were especially desired. 



As a Science, however, it has much to contend with. An animal, 

 a bird, an insect, or a plant, in almost every instance, will carry its 

 identification with the specimen. It is not always so, however, with 

 an egg. Those of many species so closely resemble each other that 

 they are often worthless unless the parent bird has been either well 

 seen or shot. It is true that the nest, together with data as to its posi- 

 tion, will frequently be of the greatest assistance in determining to 

 what species the eggs belong, but in the case of any rare and little 

 known species, the only satisfactory identification is by securing the 

 parent bird. 



The mere comparison of eggs will not answer as a means of iden- 

 tification. There is far more variation in the size, shape, and colora- 

 tion of eggs of the same species than most persons are aware of, and 

 to pick out of a large series a really typical set of some kinds is a 

 matter of considerable difficulty. 



An egg is a difficult object to properly describe, especially as it is 

 only lately that any intelligent effort has been made to set forth the 

 ground tints or the markings. 



Concerning the number of eggs laid by certain species, there have 

 been more mistakes made by writers than about any other subject con- 

 nected with Oology. Especially has this been the case with the Rap- 

 tores, and in this work the effort has been made to present reliable in- 

 formation on that point. 



J. P. N. 



