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.
