PLAN OF THE WORK 
xvii 
Descriptions of Plumage . — The descriptions, with quoted exceptions, 
are from specimens in the American Museum of Natural History, and 
my thanks are due the authorities of that instutition for permission 
to use its valuable collections. I have tried to make them as concise 
and simple and, at the same time, as detailed, as seemed necessary for 
the purpose of identification. 
It has not always been possible to describe in detail all the plumages 
assumed by a species at various ages and seasons, but at least the more 
important plumage changes, and the differences due to sex, age, and 
season are indicated. It should be explained that, where the sexes 
are alike, they are described under the subheading “Ads.” meaning 
adult specimens in breeding dress. The subheading “Im.” in the light 
Fig. 2. Spotted (a) , streaked (b) , barred ( c ) and margined ( d ) feathers. 
of our present more exact knowledge, is somewhat indefinite; but, as 
has just been said, absolute exactness in this connection is not possible 
in a book of this size, where descriptions are intended primarily for the 
purpose of identification. It may be said, however, that, with but few 
exceptions, “Im.” signifies a bird in first winter plumage, or the one 
following that (the juvenal) in which the bird leaves the nest. Where, 
however, the juvenal plumage is worn for some time, as with the Snipe, 
in which it largely takes the place of a first winter plumage, then it is 
described under the term “Juv.” 
Measurements . — All the measurements given are in English inches 
and hundredths. Those of birds are average measurements, taken for 
the most part from specimens in the American Museum of Natural 
History. I have also, with the author’s permission, made use of the excel- 
lent series of measurements in Dr. E. A. Mearn’s Birds of the Hudson 
Highlands. A variation of about ten per cent from the figures given may 
be expected. 
The total length (= L.) of a bird is found by gently stretching the 
specimen, laying it on its back, and measuring the distance from the 
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