Dale, F. H. 1955. The role of calcium in reproduction of the ring-necked pheasant. The Journal of Wildlife Management 19:325-331.
The understanding as to why Phasianus colchicus are abundantly found in some regions of North America is well understood. However, wildlife biologists are baffled by the bird’s population and distribution on a local scale. Different regions of the United States have different factors as to why the bird population is decreased. In the southeastern states, summer temperatures are too high for the Phasianus colchicus to reproduce successfully. In the West, the birds are limited by irrigated farming areas, causing a lack of water. Areas such as the Midwest and the northeast, have no clear correlation between reproduction levels of the Phasianus colchicus and environmental factors.
Phasianus colchicus are widely found in the southeastern counties of Michigan but are sparsely found in the southwestern counties of the state. Scientists suggest that some of these areas may have been influenced by glaciers at one point or another. In these glaciated areas, it is thought that limestone have been supplied. However, there is no hard evidence to back up this claim. The Gamebird Ecology and Nutrition Research Project at the Patuxent Research Refuge chose to study the role that calcium played in the successful reproduction in Phasianus colchicus.
To carry out the investigation, the scientists divided the study into two separate parts; observational and experimental. The observational portion of the study was conducted in two different field areas. One area selected was located within limestone valley (the New Holland area), and the other was in the Piedmont area, which was lacking the presence of limestone. Both of these areas were used to try to find a correlation between soil type, land-use, composition of crops, cover patterns, crop harvesting methods and then number of pheasants distributed throughout that region. Five different corn-harvesting methods were a part of the New Holland region. Since it is hard to count every single Phasianus colchicus within the ranges of the selected areas, the observation teams decided to count the number of Phasianus colchicus seen roadside. The results of the observational method showed that the percent of Phasianus colchicus was higher in the New Holland area (which contained the limestone valley), and relatively low in the Piedmont area.
The second portion of the study was experimental. Each year 80 Phasianus colchicus were distributed throughout four pens. During the first year, the birds were divided up into the pens according to sex. However, this division was not ideal, whereas the roosters had to be removed from the pens to prevent fighting during mating season. The second year of the study, the number of birds in the pen had been changed to 17 hens, and 3 roosters. During mating season, the number of hens was reduced to 12 and the roosters were reduced to one per pen. The floors of the pens had to be covered in a wire-mesh to prevent the consumption of nutrients from the soil, or ground. Two different diets were tested the first year. Both diets consisted of 65% corn, 20% wheat, 10% oats, and 5% alfalfa. The only aspect that varied between the two diets is that diet “A” was from the limestone valley, and diet “B” was from the Piedmont area (no limestone present). After the first year, it was observed that the diet itself did not play as big of a role as the type of grit that was incorporated into the diet. Crushed limestone was added into the “A” diet, and granite grit was added into the “B” diet. These diets remained consistent throughout the whole study, meaning they stayed the same through winter and breeding season. The scientists kept records on food and total grit consumption as well as general appearance, feathering and behavior of all the Phasianus colchicus.
At the end of the study, it was noted that though the pens were large enough to contain all of the Phasianus colchicus. However, even with plenty of space, there was a higher than average amount of cannibalism and feather-picking amongst the Phasianus colchicus. The pheasants tended to stick to the outer edges of the pens, which led to overcrowding. Overcrowding along with a poor diet, in comparison to other domestic poultry, surprisingly did not inhibit the Phasianus colchicus from gaining a good amount of weight. Throughout the winter, the type of diet and added grit proved to not have any effects on the birds. When laying season came around, the Phasianus colchicus being fed “B” diet with the added granite grit appeared to be less alert than that of the group that was eating “A” diet with added limestone. When laying season came around, it was clear that the groups being fed “A” diet with limestone had a higher egg laying rate, with a higher percent of eggs hatching compared to the Phasianus colchicus that were being fed the “B” diet with granite grits. The group being fed the “A” diet also had a higher rate of ovulation in the hens, leading to a higher reproduction rate as well.