JFor Ceaci)erg anti ^tutients; 



How Birds Molt 



BY JONATHAN DWIGHT, JR.. M.D. 



IN spite of much that has been written in the past about the molting 

 of birds, the subject is by no means threadbare, and I hope that a 

 brief sketch of the compHcated process of feather -renewal will 

 stimulate interest in its further study. Periodically, old plumage is cast 

 aside feather by feather as new ones grow, and so gradually does this 

 take place that most birds are able to fly about as if nothing unusual 

 were in progress. Many species (among them the Thrushes, Wrens, 

 Blackbirds, Jays, Woodpeckers, Hawks, Owls, and a few others) wear 

 only one plumage throughout the year, exchanging the more or less 

 ragged remains for a fresh suit at the end of the breeding season ; while 

 many Warblers, Sparrows, Waders and others molt part of their body 

 plumage a second time in the winter or spring. These two molts are 

 the postnuptial and the prenuptial, giving distinctive winter and summer 

 plumages. 



Two plumages are peculiar to young birds — first, the natal, the stage 

 of soft, downy baby-clothes, and, second, the juvenal or knickerbocker 

 stage. The weak, juvenal feather of a young Purple Finch is shown by 

 the half-tone which is from a photomicrograph. Both plumages of young 

 birds vary greatly in dif^ferent species. We are familiar with the little 

 tufts of natal down scattered on nestling Sparrows, Thrushes, or Warblers, 

 and the dense covering of Ducklings, Gulls, Game-birds or Hawks and 

 Owls. In Woodpeckers it is aborted. 



The juvenal plumage, delicate and transient in most land birds, may 

 be worn wholly or in part for many months in large species, and is often 

 confused with other plumages. If, however, we bear in mind that there 

 is nothing haphazard in the growth of feathers and the sequence of molts 

 and resulting plumages, our ideas upon the subject will become very 

 much clearer. At a definite time and at a definite point of the skin, 

 each ^nd every feather grows, and plumages are only successive generations 

 of feathers. 



Abrasion, attrition and weathering of feathers go to make up wear 

 which sometimes produces surprising color-changes in plumages. The 

 loss of the brown feather edgings of, for instance, the fall Snowflake or 

 Red -winged Blackbird, displays the black hidden beneath, and the loss of 

 the little barbules of the feathers of Crossbills or of the pink Purple 

 Finch brightens red colors by subtracting the gray tints. The first 



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