Pheasants and Hungarians 127 



Nutritional Hypothesis. H. L. Stoddard and the author presented the 

 glaciation hypothesis, and the facts of behavior noted in this chapter, to Prof. 

 J. G. Halpin, head of poultry husbandry in the University of Wisconsin. We 

 asked him to describe to us any experiences with poultry which might throw 

 light on the subject of exotics, especially on the contradictory behavior of cap- 

 tive and wild pheasants respectively in the southern zone of failure. 



Professor Halpin stated that nutritional deficiencies in poultry often do not 

 show up until the second or third generation. This may be the key to the riddle. 

 For instance, chickens deliberately fed a ration deficient in a certain respect may 

 continue in good health, and may exhibit normal breeding, but the progeny will 

 lack size or -vigor. Sometimes the deficiency will not show up until the second 

 generation. In one experiment a certain ration which showed excellent results at 

 the end of three weeks, caused death at the end of 20 weeks. The poultry 

 evidence is far from complete, but tends to show that: 



(1) Good nutrition of poultry (and also of cows, pigs, and humans) ap- 

 pears to depend not only on chemical composition of the ration, but also on the 

 chemical state of the food compounds it contains, and the ratio between them. 



(2) Normal birds appear to carry a reserve of certain unidentified food sub- 

 stances. 



(3) When the ration lacks one of these, the bird draws on its reserve. 



(4) The quantities needed for vigor may be so minute that some reserve may 

 be transmitted to the egg, and thus invigorate the first generation. 



(5) Ultimately, however, the reserve is exhausted and a marked decline in 

 size, vigor, or reproductive capacity results. 



(6) Rations deficient in mineral substances like lime exhibit this delayed 

 effect most clearly, but rations deficient in certain vitamins also show delayed 

 effects. 



Here, then, is a possible explanation of the contradiction between captive 

 and wild birds. Captive pheasants on game farms often receive imported foods, 

 and the stock is almost always annually replenished by the importation of breed- 

 ing stock from other, and usually northern, regions, which may transmit small re- 

 serves of deficient food substances to the eggs and thus maintain at least a cer- 

 tain degree of vigor. Wallace Evans has long ago called attention to the varying 

 size of both wild and captive pheasants in different regions, and ascribed the 

 variations to soil. This may reflect simply different degrees of nutritional de- 

 ficiency. 



Planted pheasants usually come from the northern zone, because that is 

 where most game farms are located. They may be assumed to bring with them 

 certain nutritional reserves which allow of vigorous breeding the first year, even 

 in the south. By the second or third generation these reserves become exhausted 

 and the plant disappears, unless re-invigorated by follow-up plants of northern 

 stock. A few adult stragglers may survive because their reserves lasted longer, 

 but eventually they all disappear. 



