THE OOLOGIST. 



79 



Albinism. 



BY C. J. MAYNAKD. 



NOTICE in The Oologist for Sep- 

 tember, '77, an item in an article by 

 iiu-p_ Mr. W. H. Ballou, relative to the 

 capture of an albino Blackbird. Without 

 pausing to discuss Mr., Ballou's theory, that 

 this instance oi' albinism was caused by the 

 "■union of its parent with a Snow Bunting," 

 for I know that, upon reflection, he will see 

 the absurdity of advancing this hypothesis, 

 I will at once proceed to what I have prov- 

 ed to my complete satisfaction, by long 

 •study of this subject, to be the facts of the 

 case. 



Albinos, among birds, consist, as every- 

 one should understand, of specimens which 

 have a portion or all of their fefYthers whit- 

 ened ; the bird so marked being perfectly 

 normal in other respects. I find that albi- 

 nos may be divided into two classes : those 

 in which the feathers are thus affected by 

 deci'epitude, and those which, though in the 

 full vigor of life, have feathers that are 

 whitened by what we may consider as an 

 abnormal condition of the vessels which 

 supply the growing feathers. 



Those affected by age are also of two 

 kinds : 1st, Birds which have become so 

 old as to be incapable of moulting. It is a 

 well known fact that all birds, when in a 

 healthy condition, moult once or twice an- 

 nually, but in the cases under consideration, 

 the vital energies of the individuals have 

 become so nearly exhausted that they 

 are not able to undergo this necessary 

 change, and the plumage, from constant 

 exposure to the sun and weather, becomes 

 very much bleached. 



If a brightly colored bird, like an Oriole 

 or Tanager, in perfect health, be examined 

 just before the time of moulting, the plu- 

 mage will be found to be noticeably paler 

 than it was earlier in the season, and if the 

 moult did not occur the feathers would be- 

 come nearly Avhite. It is quite unusual to 

 find albinism In this condition, but I have 



seen two or three instances. The reason 

 for not finding more birds which are so old 

 as to be unable to moult, may be explained 

 by the fact that the time for casting the 

 feathers and renewing them, is a critical 

 period in the lives of aged specimens, and 

 many die in making the effort, while those 

 which survive the failure are very few. 



Second, aged birds, which, although ca- 

 pable of undergoing the regular moult, lack 

 sufficient vigor to supply the requisite col- 

 oring matter ; the plumage is therefore very 

 pale. I have seen several Tanagers (Py- 

 ranga ruhra) which were good examples of 

 this, the parts which are usually bright 

 scarlet being in these cases yellow. The 

 fact of brightly-colored caged bii'ds frequent- 

 ly assuming a paler plumage after moidting 

 in confinement, may be attributed to this 

 cause . 



In the second class of albinos, the feath- 

 ers are usually, though not always, pure 

 white. We may also divide this class into 

 two kinds : 1st, those which ai-e only part- 

 ly albinos. In cases where single feathers 

 or patches of them are whitened, we nuist 

 look for local causes. Whenever a bird 

 drops a feather, a new one quickly appears 

 in its place. This is quite short at first, 

 but perfectly developed as far as it has ad- 

 vanced. It tiuis pushes outwards until it 

 has attained its full length. Now, if we 

 examine the half grown feather, we find 

 that the basal extremity consists of a tube, 

 which contains a system of blood-vessels 

 that fui'nish the supply, of which the vari- 

 ous parts are constructed. Thus, the elas- 

 tic, horny portions of the shaft, the downy, 

 wavy plumes of the accessory feathers, and 

 the brilliant colors which so often dye the 

 webs, are all manufactured, so to speak, 

 in some mysterious manner from the blood 

 supplied by this system of vessels, which, 

 when the feather attains its full size, are 

 compressed gradually by the contraction 

 of the cylindrical shaft, and thus being cut 

 off, become absorbed, or more properly, 

 withdrawn, to remain quiescent until the 

 next moult occurs. 



If we examine this arterial system, we 



