For birds that do not migrate to warm climates during winter, life can be brutal. Survival depends on finding adequate food and shelter. Survival rates of ground feeders such as pheasants are high during mild winters when deep snow does not persist for more than a few weeks. This has been the case in each of the past four winters in southern Minnesota. On the other hand, 60-90 percent of pheasants die during severe winters like the one we had in 2000-2001 because persistent, deep snow buries most food and cover. Pheasant survival during severe winters can be enhanced by providing good cover and a dependable source of food, such as a corn food plot, that is adjacent to shelter. In contrast, ruffed grouse thrive during winters that are deadly to pheasants. With deep snow, ruffed grouse use snow burrows to provide shelter from the weather. Furthermore, ruffed grouse feed on tree buds, which remain available regardless of snow depth.
http://www.justnorth.com/Articles/ArticleLibrary/tabid/612/articleType/ArticleView/articleId/1023/How-do-pheasants-survive-winter.aspx
