If winter came too early for you this year — before you'd finished all the yard chores and dug out your mittens — consider how it affected wildlife. Some hibernating animals weren't done winterizing either. Other creatures suddenly couldn't get groceries anymore. And a few species of birds were scheduled to fly out of town a couple weeks later, only to find themselves stranded, burning precious fuel (otherwise known as body fat) just to stay warm.

Some of those animals found their way, via human transport, to the Wildlife Rehabilitation Center of Minnesota in Roseville. During the November 2014 snowstorm, the center admitted numerous stranded birds, including a rufous hummingbird that took shelter near a heated birdbath and a loon that was rescued off Upper Bottle Lake by a family who'd watched the juvenile since it hatched last summer. They became alarmed when they saw the loon swimming in a shrinking circle of open water. The center's veterinarians discovered that the bird had an old wing injury. After some physical therapy, they hope the bird can be released in the Gulf of Mexico, where Minnesota loons spend their winters.

The center just wrapped its busiest year ever, with 9,200 animals admitted. It's best known for its busy wildlife nurseries in the spring and summer. About two-thirds of all animal admissions are orphaned or injured baby birds and mammals, which an army of volunteers care for and feed one wiggly mealworm at a time.

The center is open 365 days a year, and winter brings a slightly different cast of clients. "We treat about 50 swans every winter now, and that's become very interesting," says executive director Phil Jenni. "Fifty years ago, there were none left in Minnesota, so they've made a comeback. The problem is, they stay around open water, which tends to be around the power plants. But of course, that water is crisscrossed with high lines and so we see a lot of power line strikes — serious burns and other injuries.

"The availability of lead in rivers and streams is another big problem" for swans, says Jenni. "Years of fishing and hunting have led to an accumulation of lead in our waterways and first-year swans especially are attracted to that lead. When they ingest it, they get emaciated and depressed and have eating and flight problems."

Jenni notes that Minnesota's winter wildlife is well adapted to the cold. The real problem is when food sources become scarce. That's when songbirds might venture to feeders closer to our houses, where they're at greater risk of striking windows. Or loons might get stranded on parking lots or cornfields, which they mistook for water. "Loons and grebes need a long stretch of water, like a runway, in order to take off," says Jenni.

Lake Michigan doesn't usually freeze, but it did last year. Starving waterfowl flew inland in search of food, which was no more available on Minnesota's frozen waterways. Tens of thousands of mergansers, loons, grebes, scoters and other diving waterfowl winter on Lake Michigan, and ornithologists reported high numbers of bird deaths.

"This year, a lot of migrants got caught because of the cold snap," says Jenni. "But a lot of those animals had underlying conditions that made them more vulnerable. Their immune system had been compromised or they had wing issues, an old injury. Most of them just die, unseen by the public."

In nature, that would be called strengthening the gene pool. By weeding out the small, weak or imperfect, the next generation has a better chance of enduring whatever winter dishes out. So the argument can be made that when we help a wild animal, we are doing more harm than good. The wildlife center sees misguided helpfulness in action every spring, when numerous perfectly healthy fledgling birds and young fawns are brought in by people who assumed they were orphaned.

"About five years ago, we started doing a lot more educational outreach to let people know they should leave those babies alone, because very likely a parent was nearby, and that parent can do a much better job of raising their baby than we can," says Jenni. "Many birds will watch and feed a fledgling from a nearby tree. Deer and rabbits hide their babies and then leave them alone for long periods so they don't attract predators. After we got the word out, we saw a drop of about 300 cases a year as people made the right decision to leave those animals be, and let nature do its thing."

On the other hand, many animals come in with injuries that were caused by humans, not by nature. Each year, the center admits birds caught in fishing lines or poisoned by ingesting lead sinkers and shotgun pellets; mammals hit by cars; even creatures like mice or squirrels that homeowners intended to kill, but only injured before losing the heart to finish the job. For wildlife, the vast majority of human encounters aren't for their own good.

Helping a few unfortunate animals doesn't make a big difference for the overall populations of most species. It neither weakens the gene pool nor evens the score. But it makes a difference for the individual animals and the individual humans involved.

"We don't want people to, for instance, create a hazard in traffic by helping an injured animal," says Jenni. "At the same time, though, we don't want to discourage the impulse to help. Maybe we have too many squirrels but we don't have too much compassion. Anything that exists to help nurture the human instinct for compassion needs to be encouraged."

There's another benefit to humans in caring for wildlife. Some of the diseases that affect people also affect animals. And the wildlife center is on the front lines of identifying infections in the wild. "We ID'd the first case of West Nile in a pelican," says Jenni. "If, God forbid, avian flu came here, there's a good chance we'd be the first place that confirms it. Public health is protected in part by paying attention to what's happening in wildlife."

The center is on high alert for white-nose syndrome, a disease devastating bat populations across the country with its mortality rate upward of 90 percent. It doesn't affect humans, though it threatens to eliminate one of our most powerful defenses against mosquitoes and mosquito-borne illnesses. The northern long-eared bat is proposed for listing under the Endangered Species Act; its population has decreased by 99 percent from the disease. White nose was first identified on the East Coast in 2006 and it's moving westward. Last year, DNA for white nose was confirmed in Minnesota caves.

"This has dramatically changed the way we treat bats," said Jenni. Each bat is now tested and monitored for the disease. The center admitted 227 bats in 2014, many of them during the winter months. Its very first patient of 2015 was a big brown bat. "We call them 'Christmas bats.' People go up into their attics and pull out their lights and decorations and inadvertently disturb a hibernating bat."

The center suggests leaving hibernating bats in the attic rather than disturbing them during the winter months. For the most part, the same advice holds for other wildlife. Fur and feathers do a fine job of keeping animals warm. As long as they aren't injured or ill and can access food, they should make it through to spring, says Jenni. "Winter survival is truly amazing and we should enjoy the wonderful mystery of creatures so different from us."

Amy Goetzman is a Twin Cities writer.