WATER REQUIREMENTS 243 



All this points to the conclusion that weather cycles are not likely to exert a strong indi- 

 rect influence on grouse abundance by producing periodical changes in the composition of 

 their food. But the subject is still too little understood to justify aught save an open mind as 

 to the possibilities. 



WATER REQUIREMENTS 



Water is of prime importance to the living body, for it is vital to every physiological action 

 as well as being an important constituent of the individual cells. 



Grouse may obtain water from three main sources: drinking water (from puddles, streams 

 and ponds, and also snow), dew, and succulence (water taken from plant or animal foods 

 high in moisture content). The extent to which the two latter sources can supplement or take 

 the place of the former determines the dependence of the birds upon a steady supply of 

 drinking water. 



The basic requirements of the species for water are not as yet definitely established. Ixmg. 

 in carrying out physiological experiments*, however, found that a deficiency soon made it- 

 self felt. Six adults were held without access to either food or water. After a period of only 

 3I/2 days half of them had died. On the other hand, 12 birds supplied with water, but no 

 food, were able lo mniiilaiTi normal body trm|icraliirrs for nine days and easily survived 

 the experiment. 



Birds reared at the Research Center are provided with drinking water from the time they 

 are hatched. Inasnuich as their artificial ration is low in moisture content it is not surpris- 

 ing to find them drinking freely. When the rearing of grouse was still in the experimental 

 stage the chicks were fed moist foods such as (laljbcr and fly larvae. Drinking water, though 

 available, was then onh occasionally resorted to. Adults penned in large enclosures also man- 

 aged without frequent recourse to drinking water, dew and succulence apparently satisfying 

 their needs. 



Small puddles formed by rain may be utilized by wild grouse. Bradbury'' witnessed such 

 use but despite thousands of observations the Investigation has never actually seen a wild adult 

 grouse drinking from open water. Lehmann™ similarly reported that prairie chickens rarely 

 drink from surface water, but Girard''' states that sage grouse drink from two to three times 

 daily, preferring running water to that from puddles. 



The sources from which water is available, may vary with the different seasons. In the 

 spring melting snows and heavy rains make surface water everywhere abundant. A little 

 later the succulent foods, to which the birds turn their attention after a winter-long diet of 

 browse, are high in moisture content. Aspen leaves and fern fronds are well over two-thirds 

 water. In contrast, buds and catkins generally contain less than 50 per cent moisture. The 

 amount present in 8 common spring foods all freshly gathered, is shown in figure 21. 



Summer foods are made up largely of fruits and insects for the juveniles, fruits and leaves 

 for the adults. All are high in moisture content. Raspberries and blackberries, the most com- 

 monly eaten summer food, are four-fifths water. Dandelion leaves run as high as 89 per cent. 



The moisture content of many common fall foods such as beechnuts, hard seeds and buds is 

 somewhat less. For example, sumach fruits, taken commonly at this period, are less than 10 



* Sep Appendix, p. 761. 

 A Bradbury, H. M.. persona! letter to the authors. 



