The Birds’ Calendar 
well to know the length of a few familiar birds, 
which one can carry in mind as standards of 
measure. As good as any for this purpose are 
the crow, which is about twenty inches long, 
the robin, about ten inches, and the English 
sparrow, or the song sparrow, about six inches. 
In discovering a new species one is often so 
excited as to forget entirely to make a note of 
its size, and on consulting reference - book or 
stuffed collection he finds he has neglected an 
essential point of the description, and must wait 
until the bird favors him with another audi- 
ence. 
Secondly, as regards the migrations of birds 
(for, as before shown, there is rarely a specimen 
and only a very few species resident the whole 
year at any locality in northern latitudes), the 
facts are most easily learned from books, al- 
though by a year’s careful observation one can 
quite accurately classify the summer and winter 
residents and migrants of his own region. But 
the further interesting facts of the northern and 
southern extent of their range in different sea- 
sons of the year can be learned only by the 
combined observations of many individuals 
over a wide extent of territory, and we must 
rely upon books to tell us, for example, where 
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