4 PREFACE. 



not stiff and pointed, and Part 2, tail feathers stiff and pointed. Our duck has stiff, 

 pointed tail feathers, and therefore belongs in Part 2. Part 2 contains two species; 

 one having front of head and cheeks black, the other with sides of head more or less 

 white. As our duck has a patch of white on the side of the head, it must therefore be 

 the Ruddy Duck, Erismatura rubida. 



All measurements of birds are given in inches and fractions of an inch. The 

 diagrams on page 7 will illustrate how a bird should be measured, and the chart (page 

 9) will be useful to the young student of ornithology who may not be familiar with 

 the technical terms used in describing birds. Such terms as primaries and axillars 

 should be learned at once. It is customary to indicate the sexes by the signs of 

 Mars and Venus ; the male, of course, being given that of Mars, $, and the female, 

 Venus, 9. 



In preparing the Key, a large number of birds were examined and measured. In 

 this connection, my thanks are due to Dr. J. A. Allen, of the American Museum of 

 Natural History ; and to Mr. Robert Ridgway, of the Smithsonian Institute, for the 

 loan of many specimens for examination ; and especially to Mr. William Brewster, 

 for free access to his magnificent collection in Cambridge. 



The illustrations are the work of Mr. Edward Knobel. 



CHARLES B. CORY. 



Boston, Mass., Sept. 1, 1897. 



