vi BIRDS OF EASTERN NORTH AMERICA. 
not stiff and pointed, and Section 2, tail feathers stiff and pointed. Our duck has 
stiff, pointed tail feathers, and therefore belongs in Section 2. Section 2 contains two 
species; one having whole front of head and cheeks biack, 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, Hrismatura jamaicensis. 
All measurements of birds are given in inches and fractions of an inch. The 
diagrams on page 8 will illustrate how a bird should be measured, and the chart (pages 
viii and ix) 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, °. 
In preparing the Key, a very large number of birds were examined and measured. 
In addition to the large collection of North American birds contained in the Field 
Columbian Museum, by courtesy of my friends, Dr. J. A. Allen and Prof. Robert 
Ridgway, the collections of the Smithsonian Institution and the American Museum 
of Natural History were always open to me, as well as the splendid private collection 
of Mr. William Brewster, at Cambridge, Mass. 
A few species which occur in Greenland, but which have not been observed else- 
where in North America, and rare exotic stragglers have been excluded from the Key, 
but are given in their proper place in the body of the work. 
The larger portion of the illustrations are original and are the work of Mr. Edward 
Knobel, of Boston. Numerous cuts are also included by arrangement with Messrs. 
Little, Brown & Co., of Boston, which are taken from Baird, Brewer & Ridgway’s 
Nortu American Brrps. <A few others were obtained from Messrs. Estes & Lauriat, 
used in Dr. Elliott Coues’ Key to Norra American Brirps. 
C. B. -\CORY,. 
