° 1918 ] Kennaed, Ferruginous Stains on Waterfowl. 125 



of iron. An adult Mallard drake, collected on the Mississippi Delta, 

 was badly stained all over its belly, and the dark feathers of its 

 breast, on which the stain was hardly noticeable, gave a positive 

 reaction. The white collar was badly discolored, while the iri- 

 descent green feathers of the neck immediately above the collar, 

 apparently just as glossy and green as ever, also gave a positive 

 reaction. 



In the meantime Mr. H. S. Swarth, of the University of Cali- 

 fornia, called my attention to a similar investigation away back in 

 1910 by Dr. Joseph Grinnell, which had previously escaped my 

 notice, 1 in which he writes as follows regarding the Red-throated 

 Loon, — " Common, and thought to be breeding about the head of 

 Cordova Bay. Two adult specimens, taken there June 9 and 10, 

 have the entire lower surface, where it is normally snowy white, of 

 a bright ferruginous tinge. This color is intensest on the exposed 



portions of the feathers, suggesting adventitious origin Dr. 



M. Vaygouny of the Department of Chemistry of the University 

 of California, determined by analysis that the discoloration is 

 due to the presence of ferric oxide (FeiC*3), probably deposited from 

 the water of the marshes in the immediate locality. As the Red- 

 throated Loon moults in the spring, the discoloration must have 

 been acquired since April 1 ; and furthermore, the species probably 

 does not arrive from the south until that date at earliest. There- 

 fore, the deposit has been surprisingly rapid. The iron oxide in the 

 water is said to result from bacterial action, and precipitation is 

 liable to occur freely on organic substances of certain textures. 

 Evidently the loon's feathers are especially favorable. The same 

 deposit was noticed to a less extent on certain other birds of the 

 same locality, as hereinafter noted." 



Again in the same publication, Dr. Grinnell writes of three 

 Northern Phalaropes, collected at the Head of Cordova Bay, June 

 11 to 14, which "have the lower surface of the body rusty-stained, 

 as in the case of the loons from the same place before described." 



The stain is very persistent, but invariably disappears with the 

 moulting of the feathers, when the bird is in captivity, or when the 



1 Birds of the 1908 Alexander Alaska Expedition with a Note on the Avifaunal Rela- 

 tionships of the Prince William Sound District, by Joseph Grinnell, University of Cali- 

 fornia Publications in Zoology, Vol. 5, No. 12, March 5, 1910. 



