Vol. XVII 
1900 
] Dwicut, Moult of North American Shore Birds. 369 
Such evidence as I have been able to gather is derived from 
Specimens in my own collection where age and sex have been 
determined by dissection, and from large series of skins in the 
American Museum of Natural History and the U. S. National 
Museum, which have been kindly placed at my disposal by the 
respective curators, Dr. J. A. Allen and Prof. Robert Ridgway. 
Of a few species I have examined birds taken almost every 
month in the year, but every attempt to link together the suc- 
cessive plumages is much like trying to read a book from which 
stray pages have been torn. However, I find that what is true 
of Passerine birds and of the Grouse is equally true of the Shore 
Birds, viz., that Every species has a definite sequence of plumages 
and of moults, the plumages being modified by wear and changed by 
moult. 
This principle of sequence of plumages, which I have explained 
at length in previous papers, is illustrated by a scheme of plum- 
ages and moults which was originally laid out for Passerine spe- 
eies| (Annals N. Y. Acad. Sci., XIII, rqoo.' pi 104) but ites 
equally applicable to the Shore Birds. It shows the plumages 
in their natural sequence followed by the moults that occur, unless 
suppressed, as they are in some species, and it is as follows: 
1. Natal Down. 1. Postnatal Moult. 
2. Juvenal Plumage. 2. Postjuvenal Moult. 
3. First Winter Plumage. 3. First Prenuptial Moult. 
4. First Nuptial Plumage. 4. First Postnuptial Moult. 
5. Second (or Adult) Winter 5. Second (or Adult) Pre- 
Plumage. nuptial Moult. 
6. Second (or Adult) Nuptial 6. Second (or Adult) Post- 
Plumage, etc. nuptial Moult, etc. 
Later plumages would be ‘ winter’ and ‘nuptial,’ followed by 
‘prenuptial’ and ‘postnuptial’ moults. This scheme furnishes 
definite terms which are almost indispensable for a_ proper 
explanation of the plumage changes which regularly occur as 
birds pass from immature to adult dress and from summer to 
winter plumages. 
In many species of the Shore Birds, plumage differences 
between young and old are lost at an early period. All adults 
at the postnuptial moult assume a plumage that in one class of 
