222 Thr Wilson Bulletin— No. 69. 



2, p. 198, both of whom found similar coloration in the Lesser 

 Scaup Duck (Aythya atJinis). I have observed it in several 

 specimens of Pintail (Dafila acuta), both males and females, 

 one male Mallard (Anas boschas) and to a lesser extent in a 

 male Black Duck (Anas rubripcs). The rusty coloration is 

 very pronounced in the case of the Pintails, both male and 

 female, but, of course, is more noticeable in the males, where 

 in extreme cases the white breast and neck are stained in their 

 entirety. 



One specimen in particular that 1 have before me (No. 197, 

 coll. B. R. B.), has this rusty stain on all the white parts of 

 the breast and neck, as well as (though not so noticeable) on 

 the finely barred feathers on either side of the white portion 

 of the breast. The staining extends well up upon the sides. 

 Mr. Henninger states that he does not agree with the statement 

 made by Mr. Arnow in that the coloration is due to "some 

 compound of iron in the water frequented by the birds," but 

 that "it must be due to other causes." 



Owing to the fact that this abnormality of coloring has been 

 found upon so many varieties of ducks, I was led to accept 

 the theory of Mr. Arnow, and determined to make a chemical 

 test for iron. I therefore plucked several feathers from the 

 breast of one of my Pintail skins and soaked them for several 

 hours in water slightly acidulated with chemically pure hydro- 

 chloric acid. After several hours soaking, the rusty color en- 

 tirely disappeared, the solution remaining clear. I then added 

 a few drops of a weak solution of potassium ferro-cyanide, 

 whereupon the solution turned to a blue color, showing the 

 presence of iron. The form of iron in the water at the time 

 it is deposited upon the feathers is likely the hydrate, though 

 it is possible that it may be the sulphate. As soon as the 

 feathers become dry or exposed to the air, the hydrogen is 

 lost, and the form changes from the hydrate to the oxide or 

 iron rust. 



The test employed to determine the presence of iron is ex- 

 plained thus : By soaking the suspected feathers in dilute hy- 



