124 Rennard, Ferruginous Stains on Waterfowl. [ April 



of the genus Chen, Blue Geese, Lesser and Greater Snow Geese, and 

 Ross's Geese, as well as a series of Emperor Geese, all apt to be 

 more or less stained about their heads; and a series of the Canada 

 group of the genus Branta, including the Canada, Hutchins', and 

 Cackling Geese, apparently having essentially the same habits and 

 haunts, but which nevertheless remain practically unstained 

 throughout the year. 



In view of the fact that there still seems to be a good deal of 

 uncertainty among some of our ornithologists regarding these 

 ferruginous suffusions, the following notes, in which I have tried 

 to answer the questions raised at the Nuttall Club meeting, may be 

 of interest. 



During the summer of 1917, Professor S. C. Prescott of the 

 Massachusetts Institute of Technology very kindly offered to make 

 a chemical analysis of such stained plumages as seemed necessary. 

 He examined feathers from various parts of Blue Geese, Greater 

 and Lesser Snow Geese, Mallards, Gadwalls, Blue-winged Teal, 

 Green-winged Teal, Baldpates, Shovellers, Canvas-backs, Ring- 

 necked Ducks, and Ruddy Ducks, and reported that " the results 

 of these analyses in all cases showed that the coloration was due 

 to iron, which was deposited in the form of ferric oxide (Fe20s) 

 on the tips of the feathers. The white feathers showed the colora- 

 tion most pronouncedly, as was to be expected, but even the dark 

 brown and black feathers of some species showed the presence of 

 the iron. It is easy to show by micro-chemical methods that the 

 oxide of iron is deposited on the outside of the feather, and does not 

 penetrate into the tissue." 



Professor Prescott also writes that "it seems to me quite likely 

 that different kinds of feathers from the* same bird will exhibit 

 differences in the degree of coloration they are likely to undergo. 

 The colored feathers have a different chemical structure, and will 

 be less stained, just as colored cloths will dye less readily than white 

 ones." 



One of the birds that we examined, for instance, an adult male 

 Ring-necked Duck, collected among the sloughs of the Mississippi 

 Delta, had its white belly completely covered with stain, while its 

 black breast appeared nearly as glossy as that of an unstained bird, 

 and yet these same black feathers gave a positive reaction of oxide 



