Despite a week or so of some below normal temperatures, this winter season is shaping up to be a relatively good one for most wildlife. Our snowfall so far have been of the “nickel and dime” variety with no really large single storm accumulations. For it is deep prolonged snow that can play havoc with many species of wildlife.
When major snowfalls occur early, say in late November, the deep snow covering has two negative effects on wildlife: it makes locating and reaching ground-level food difficult and also makes travel to locate it more difficult for ground-based species. Even avian species can be affected unless they can locate foodstuffs that are available above the snow line. The latter is why we see so many birds come to feeders in winter.
Another enemy of wildlife is freezing rain since it can coat the ground, as well as trees and bushes that provide foodstuffs, with ice, making it more difficult for wildlife to reach and consume vital nutrition when they need it most. It can also do the same with avian species, coating their feathers with ice and sapping their strength when trying to fly or otherwise move to different locations. If the snow is deep and a heavy crust forms, it can actually benefit smaller species that are supported by the hard layer while proving to be an obstacle to larger species that break through the crust.
The worst winters are those that see deep snow arrive early and then remain or see additional inches added on a regular basis throughout the entire season. Even if a crust isn't present, the deep snow greatly prohibits movement as well as burying ground-level food underneath several inches or feet of snow. Deer are especially impacted, and such winters can elevate mortality due to starvation. Even wild turkeys that may be able to walk atop the crust can experience high mortality rates since their primary foodstuffs are difficult to reach and cause them to burn valuable energy digging down to reach it. If dairy farmers are able to spread manure, the turkeys will pick out any residual seeds it contains. When you see turkeys moving to sumac stands during a severe winter, you know they're under duress since sumac seeds are their last resort natural food source.
Avian predators such as hawks and owls benefit since spotting prey against the snow is easier and those prey species that venture into the open with no overhead cover often become meals. Voles can benefit by burrowing and traveling beneath the snow, but should they venture on top, their odds of surviving are greatly diminished. Mammal predators such a fox and coyote find deep snow hunting less productive and often must find prey such as voles by listening for the rodent as it moves beneath the snow, then pouncing on it and digging it out. If the crust will support them, some coyotes will hunt in family packs which allows them to catch the occasional rabbit. On occasion they'll also take down deer that break through the crust and flounder as they try to escape.
In the autumn, gray squirrels often bury acorns and other mast as it falls to the forest floor. Unless temperatures are very low, the squirrels will venture out to retrieve their buried meals, but if the snow becomes too deep, locating and digging up their buried bounty becomes more difficult. The mast and acorns they fail to find often germinate and produce new trees, which is nature's way of reforestation. During extended stretches of cold, the gray squirrels will remain in their den trees, huddling together for body warmth.

Of course some species such as chipmunks and woodchucks are true hibernators, but black bears are not, although sows with cubs tend to remain in their winter dens longer. Boars or cubless sows will often venture out during a mid winter warm spell, more to “stretch their muscles” than to seek food. However, once warmer weather arrives the bruins will have used up all their body fat acquired in late summer and fall and will be hungry. This is when they show up near residences that offer bird seed or suet, or unprotected garbage or pet food left outdoors.
Now some scientists believe that areas experiencing global warming could see it affecting hibernating animals, causing them to wake up earlier. While this may seem a trivial concern, it is in fact a legitimate environmental problem. The shortened hibernation period could actually lead to significant declines in the populations of several species. Species, including marmots, chipmunks, and brown bears, have all been seen to either reduce their hibernation period or not hibernate at all. This can cause starvation and possibly increased numbers of some animals being eaten by predators.
Some of the first concrete evidence of the phenomenon came from Colorado, where researchers at the Rocky Mountain Biological lab have been observing marmot hibernation behavior since the 1970s. In the early days of their studies, marmots generally hibernated several weeks into the month of May. Nowadays, however, temperatures in the area have risen by 2.5 degrees F, and the marmots are waking up about a month earlier.
I'm pretty sure that most of us won't complain if this relatively mild winter continues, and I'm also sure our neighbors in the wild kingdom won't. After all, with us it's a matter of economics and comfort, but with them, it's more a matter of life and death.