'899 



Birtwell, An Example of Aptosochromatism. 3*7 



still present, as before the increased feather loss. This condi- 

 tion prevailed until the effects of the liver diet begun on Dec. 

 25, 1898, began to be felt. For 154 days, or until May 28, 1899, 

 this food was kept up. Then through necessity I was obliged 

 to discontinue it as the bird, tired of its one-sided fare, fasted 

 for three and four days together repeatedly and often only tore 

 the food up into small pieces without eating it. By the above 

 date, however, about 12 lbs. of liver were eaten. Feb. 22, 1899, 

 the bird was very noticeably rufous colored from a distance, and 

 this intensified with time, although the color never became pro- 

 fuse enough to cause a general resemblance to the color of the 

 extreme typically red phase as found commonly in the wild state. 

 Especially prominent were the rich borders of the two black 

 spots of the upper breast, and as in the first red state — the 

 colors of the ear tufts were markedly changed. During the 

 latter few weeks, the change was very slow and it was very diffi- 

 cult to get the bird to eat. By May 28, however, he was much 

 more strongly colored with rufous than before. 



The beef was again put on and rapidly the bird assumed the 

 dusky state and was immerging from this when, as has been 

 before explained, I was obliged (July 22, 1899) to let it go. The 

 bird flew off swiftly and in its wake the majority of House Spar- 

 rows of the vicinity. In this case, 55 days had elapsed since the 

 change of diet, and 45 ounces of beef had been eaten. 



In the back feathers the contrasting colors of the two diets were 

 very plainly in evidence, the dull brownish areas of the feathers 

 of the beef diet, being strongly shot with reddish in the feathers 

 under the influence of liver. 



Once, for a week, I tried the effects of bread soaked in blood 

 but this food was emphatically rejected. It would have been 

 interesting to have noted the effects caused by a fish diet, or a 

 mixed one, and it is to be hoped that these will be carefully tried 

 at some future time. The forced and one-sided diet appears to 

 be the only marked departure from the ordinary mode of living 

 which would be powerful enough to influence my Owl in such a 

 marked degree, and I confidently believe it to be, at least, the 

 principal cause. While these results do not for a moment attempt 

 an explanation of the occurrence of the two phases in nature they 



