THE BOHEMIAN WAXWING: A COSMOPOLITE 455 
nestlings that has been taken, four of the five birds have 
the waxen wing tips at a maximum of perfection, and in all 
five the yellow markings are at a maximum of intensity. 
One can hardly lay down a scheme of consecutive plumage 
changes that will fit these facts! 
Whatever the explanation may be, it is not one that has 
been generally applied to other species of birds. It may 
be that variation is individual. That is, that the plumage 
first acquired by any one individual, a the “wax” tips 
of any given number, the yellow of any given shade, is the 
sort of plumage that is carried through life. Or it may be 
that the various ornamentations are at their best in the 
juvenal plumage and diminish with the years. The clue 
is to be found in a study of molting birds. 
In this connection a word of warning seems justified. 
Plumage change in birds, always puzzling, has on the whole 
occasioned some of the most careful studies of any phase 
of ornithology, and as a result the sequences of plumages 
in most of our common American birds are pretty well 
known. This is not true of all species, however, and it is not 
true of a number of species of which various plumages are 
confidently described and explained in many books. Just 
as was the case with the Bohemian Waxwing, in certain 
other variable species the several plumage stages are de- 
scribed and assorted, each stage is regarded as indicating 
a certain age, and on this basis, with apparent unconscious- 
ness of the circular reasoning, a statement is made of the 
years required for that species to reach its most perfect 
plumage. The sort of facts that are needed are those to be 
obtained only from specimens the ages of which are definitely 
known, not guessed at from external appearances, and such 
specimens usually form but a relatively small part of a 
collection. 
