FEEDING HABITS 



195 



Some of the better known toxic plants, their poisonous properties and their use by grouse, 

 are shown in table 24. 



TABLE 21. PROPERTIES OF SOME POISONOUS PLANTS EATEN BY GROUSE 



Interesting to note is the presence of salicylic acid, the active ingredient of aspirin, in 

 aspen leaves. In spite of the bitter flavor thus imparted to these leaves, they rank among the 

 ini|)ortant sources of summer foods. However, willow leaves, with a slightly higher conren- 

 tration of salicylic acid, are rarely touched. Leaves of sheep sorrel I Ruinex acelosella) and 

 wood sorrel (Oxalis), sometimes eaten in large quantities, contain oxalic acid, but since cal- 

 cium oxalate is highly insoluble it is doubtful if Ictluil qimiititics of the acid are released 

 during digestion. 



The deadly hydrocyanic acid is one of the dpc(iin|)ositioti products of chcrr\ leaves, formed 

 by the action of enzymes upon the glucoside, amygdalin. While wiUed leaves are the most 

 dangerous, the vigorous succulent leaves from young shoots are far more poisonous than foli- 

 age from a mature or stunted tree. Perhaps, then, there is some significance in the fact that 

 not once was the presence of cherry leaves detected in the course of the analyses. On the 

 other hand, the fruits and the buds and twigs of cherries are among the most popular grouse 

 foods in New York, so there is amitlc opportimilv for grouse to sample llicm. Other types 

 of foliage are browsed, often extensively. l)ut tlial the birds here draw the line is an evident 

 but unexplained mystery of bird j)sychol<igv. Ain\gdaliii is likewise ])reseiit in the kernels 

 of the cherry pits, which are often broken open in the muscular gizzard. Either the quantity 

 of hydrocyanic acid produced is too small or conditions are not satisfactory for its libera- 

 tion, for the birds seem to experience no ill effects from digesting them. 



Two other common plants in New York are ignored by grouse — the conspicuous bright blue 

 fruits of cohosh (Caulophyllum thalictroides) and the well-known mandrake, or May-apple 

 f Podophyllum prllalitm). The former contains the alkaloid methylcvtisine. and the latter 

 podophyllin. Bolh are purgatives and overdoses may pro\e fatal. Ripe fruits of the latter 

 are edible, although a severe dermatitis may be produced from handling the rootstocks. 



Animals, too. may contain unpalatable substances. Ants are often spoken of as "pro- 

 tected" insects due to the presence of formic acid, but more grouse feed on ants than on 

 any one other kind of insect. Caterpillars armed with poisonous spines, and stinkbugs, are 

 often eaten. 



Effect of Certain Poisonous Chemicals 



Grouse are surprisingly resistant to the chemical poisons which are employed against nox- 

 ious insects, predators, rodents and weeds. Probably the only ones possibly injurious to grouse 



