])lays in reproduction than in any other process. To 

 obtain a picture of the importance of calcium in repro- 

 duction of the pheasant, we must draw hea\ily from 

 literature on the domestic chicken {Gallus domesticus) 

 and, also, we must assume that the physiological proces- 

 ses of the pheasant approximately parallel those of the 

 chicken. 



About 98.2 per cent (2.2 grams) of the shell of the 

 egg laid by the domestic hen consists of calcium; ap- 

 proximately 6.0 per cent of the contents of the egg is 

 calcium (RomanofT & Romanoff 1949:353-354). This 

 calcium comes either directly from the daily diet of the 

 hen or from her body reser\es of calcium; the body re- 

 serves are, of course, dependent upon the calcium intake. 

 Prior to the onset of laying, the hen will store a reserve 

 of calcium along the shaft cavities of the long or medul- 

 lary bones; this deposition of reserve calcium is under 

 the control of estrogens (Hohn 1961:109; Marshall 

 1961:196). 



The circulatory system transports calcium from the 

 \iscera or the bones, or both, to the oviduct, where the 

 calcium is deposited on and in the egg as calcium car- 

 bonate and other calcium salts. The shell gland of the 

 o\iduct is about 20 per cent efficient in removing calcium 

 from the plasma in the blood stream during early as well 

 as late stages of shell formation (Winget, Smith, & 

 Hoover 1958:1327). 



Common (1943:218-219) demonstrated that the 

 a\erage daily retention of calcium from the food of 

 laying hens was about 50 per cent of the intake if the 

 daily intake averaged 1-3.5 g, but that on days of shell 

 secretion the retention of calcium might rise to about 70 

 per cent. He found that, whenever the average daily 

 intake was as low as about 2 g calcium, mobilization of 

 the reserves of skeletal calcium was practically certain; 

 he estimated that a daily intake of 4 g calcium might 

 suffice to protect the skeletal reserves of hens on sus- 

 tained schedules of egg laying. Tyler (1940:211) re- 

 ported that in the laying hen no more than about 1 g 

 calcium can be withdrawn from the bones on any day 

 the hen lays an egg and no more than about 1 g cal- 

 cium can be deposited in lier bones on any day she does 

 not lay an egg. Approximately 25 per cent of the body 

 reserves of calcium (about 98 per cent of which is 

 found in the skeleton) at the commencement of laying 

 can be used in egg formation (Common 1938:354-357) ; 

 under favorable conditions, prelaying storage of calcium 

 in the body of the hen is sufficient for the laying of 

 about six eggs. That prelaying storage of calcium suffi- 

 cient for about six eggs takes place in pheasants, also, is 

 indicated by the findings of Harper (1964:267), who 

 reported that the amount of calcium found in the grit 

 from gizzards of wild pheasant hens increased from less 

 than 1 per cent to more than 2 per cent after the hens 

 had laid six or seven eggs and remained relatively stable 

 until the second or third day of incubation; midway 

 through the 23-day incubation period, the amount of 

 calcium found in the gizzard grit of wild hens decreased 

 to near zero. 



Phosphorus as will as calcium is mobilized during 

 egg formation in some birds (Marshall 1961:197) and 

 is closely associated with the calcium complex. If a 

 diet is deficient in calcium during the period of egg lay- 

 ing, phosphorus is excreted more rapidly than normally 

 (Common 1936:96) and may even be drawn from the 

 body reserves (Romanoff & Romanoff 1949:240). As 

 with reserves of calcium, reserves of phosphorus must 

 be replenished through the diet. 



Although a deficiency of calcium has ne\cr been 

 detected in populations of pheasants in the wild, dietary 

 le\els of calcium below which penned pheasants cannot 

 carry on normal reproduction have been reported by 

 several investigators. In an experiment with penned 

 pheasants. Dale & DeWitt (1958:293) found that dur- 

 ing the reproductis-e season 600 mg of calcium per kg 

 of body weight per day (calculated by us to be equiv- 

 alent to 1.2 per cent of the diet) and 385 mg of phos- 

 phorus per kg of body weight per day were necessaiy to 

 insure satisfactory production of pheasant eggs and young 

 from hens that had received adequate calcium and 

 phosphorus during the previous winter. In another ex- 

 periment with penned pheasants, Greeley (1962:188- 

 190) found that a diet containing 1.09 per cent, or less, 

 calcium resulted in reduced (i) egg production, (ii) egg- 

 shell thickness, (iii) weight of eggs, and (iv) ash content 

 and weight of tibiae and femora of laying pheasant hens; 

 a diet containing 2.01 per cent calcium seemed adequate 

 for normal reproductive activities of penned pheasant 

 hens. 



The level of calcium required by wild pheasant hens 

 to complete successfully the annual reproductive cycle 

 has not been measured directly. Without doubt, some 

 of the calcium required by wild hens, as well as by 

 penned birds, must come from the daily diet and some 

 fiom the body reserves. Throughout much of the pheas- 

 ant range in the United States, cereal grains, which are 

 notably low in calcium, comprise a large percentage of 

 the diet of the pheasant. Trautman (1952:25-26) in 

 South Dakota and Fried (1940:30) in Minnesota re- 

 ported that grains comprised 81.7 and 81.3 per cent of 

 the annual diet of phea.sants in their respecti\e states. 

 Dalke (1937:204) reported that grains constituted 74.0 

 per cent of the annual diet of pheasants he studied in 

 southern Michigan. 



Dale (1954:318) estimated that calcium made up 

 approximately 0.23 per cent of the annual diet, includ- 

 ing all food items, of the pheasants studied by Traut- 

 man in South Dakota and by Dalke in Michigan. Harper 

 & I.abisky (1964:726) found that, in the established 

 ])hcasant range in Illinois, calcium comprised 0.21 per 

 cent of the food items from the crops of hens collected 

 during the nesting seasons (May and June) of 1961 

 and 1962. If the calcium rc(|uirements of wild pheasants 

 are similar to tho.se of penned pheasants, then olniously 

 the food items consumed by wild pheasants do not supply 

 sufficient calcium to allow normal reproduction, and a 

 su])|)lemental source of calcium must be available to lay- 

 ing hens. The belief among most biologists who have 



