294 NATATORES. 



entirely white. The plumage of the young birds resembles 

 that of the old ones in winter. It is more mottled with black 

 in the southerly than in the northerly breeding places ; but 

 whether the young are entirely white in their first plumage 

 in any latitude, has not been observed. It does not appear 

 that either of the changes of the plumage is the effect of a 

 moult ; for if that were the case the birds would, with the 

 exception of a few months in summer and a few weeks in 

 winter, have to be continually moulting. As soon as the 

 cold weather begins to set in, the white begins to appear, and 

 gradually extends itself over the feathers, which were pre- 

 viously black : and it is probable, that as these feathers 

 become white, they become more dry in their substance, 

 which will render them still better protection against the 

 cold. The young feathers continue to grow in winter between 

 the old ones : and about the turn of the year the end of 

 January or February the dark points of them appear from 

 under the white ones. It is probable that then the white 

 feathers begin to moult off ; for we have no fact from which 

 we can conclude that pale feathers in the common plumage 

 of birds, ever turn to dark ones ; and analogy the analogy 

 of all nature points to the opposite conclusion. 



We must not confound these seasonal changes in the general 

 plumage of birds with the sexual, which take place in par- 

 ticular portions of the plumage only, are most conspicuous 

 in the male birds, and bloom and fade with the breeding 

 season. These nuptial changes, whether they consist of new 

 and finer tints, produced feathers, or feathers which belong 

 to that season only, are no doubt results of that season ; but 

 they are not occasioned by it directly, but by its influence 

 upon another part of the organization of the bird ; and their 

 nuptial ornaments, in some cases, fade not only before the 

 winter begins to set in, but before the summer bird has 

 arrived at its maximum. The change which takes place in 



