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How did a warm fall and early winter impact the natural world?

Weather affects animal behavior, river levels, bird migrations, plant life

Winter has finally arrived, but not before unseasonably warm temperatures the last few months caused strange things to happen out on the landscape in Southwest Colorado.

From delayed elk and bird migrations to bears denning up later than normal to flowers sprouting to life in December, higher than average temperatures have a way of tweaking the way the natural world works.

During the month of October, for example, temperatures were 3 degrees higher than normal, historic averages, according to a weather station at the Durango-La Plata County Airport. In November, they were 2.5 degrees higher than normal.

Add the lack of precipitation, and it gets worse. Through October and November, just 1.44 inches of precipitation was recorded at the airport gauge, down more than an inch and a half from historic averages.

As a result of a prolonged drought, local rivers are at all-time lows for this time of year, typically perennial streams have been drying up and fuels on the forest floor are bone dry.

Several wildlife researchers, public land managers and biologists weighed in on what they’ve seen out in the backcountry in Southwest Colorado.

Animal life

Bryan Peterson with Bear Smart Durango said the last bear sighting of the season he received was Dec. 2, after a bear reportedly got into some trash and was investigating a chicken coop in north Durango.

While it’s not totally uncommon for bears to be out in December, it’s likely the combination of warm temperatures, lack of snow on the ground and available food, this time in the form of human trash, kept the bear from hibernating.

“It wouldn’t be surprising that some males are still out, but for the most part, I imagine the majority are denned,” he said.

Michael Remke, forest health research associate with Mountain Studies Institute, said he observed the lack of water forcing many animals, such as the blue grouse, to stay near drainages and at lower elevations from where they normally are late in the season.

“They were effectively using their spring use areas in the fall,” he said.

Nathaniel West with the Bureau of Land Management’s Tres Rios Field Office said the situation is a little more nuanced with big game.

Mule deer, for instance, migrate regardless of temperatures, and are instead inclined to move from higher to lower elevations based on day length. But elk, on the other hand, will stay in the high country until forced out by snow.

“These species have been around thousands of years,” West said. “They’ve seen wet winters. They’ve seen dry winters. They’ve seen it all.”

Fish life

Lower flows in local rivers and streams mean more water temperature fluctuations and fewer deep pools where fish can find refuge, both stress-inducing factors, said Jim White, aquatic biologist for Colorado Parks and Wildlife.

Also, even though fish metabolisms drop because they are cold-blooded animals, they still need to eat during the fall and winter, and with less water, fish can’t access shallow parts of the stream where aquatic bugs live.

Dave Sugnet fly-fishes in the Animas River on Dec. 9 in Durango, when daytime temperatures reached the low 50s. The lack of precipitation in Southwest Colorado this fall has left rivers near all-time lows.

With warm temperatures during the day and cold temperatures at night, the bottom of the river – rather than the top – can start to freeze, which can impact fish eggs incubating in the gravelly river bottom.

“That can be pretty devastating to fish,” White said.

The favorable sunny conditions also led many people to fish later than normal this year. But White said it’s less of a stress factor to fish in the late fall rather than during peak summer when water temperatures are high.

“It’s probably a good time to fish,” he said.

Corey Ertl, acting range program manager for the U.S. Forest Service, said this year, he heard reports of reliably perennial streams going dry from longtime ranchers who use public lands to graze their livestock.

“I heard a handful of comments (from ranchers) about water sources and streams going dry they hadn’t seen in their lifetime,” he said.

Plant life

MSI’s Remke said this year there was quite a bit of “strange phenology,” which is basically the study of the timing of biological events in plants and animals.

The Old-Man-of-the-Mountain alpine flower, Remke said, was blooming in late May/early June, before it was hit by frost in late June. Even this reporter spotted a live, flowering dandelion up Hermosa Creek the first weekend of December.

Remke said these strange phenology events can be harmful to some plant populations, whereas others are more tolerant of abnormal weather conditions.

Plants that tend to be widely distributed seem to be less sensitive, Remke said, whereas plants that live within a specific elevation or climate niche tend to be more sensitive.

“This year – it seems – everything was about water,” he said. “Plants did their phenology when they had moisture for it, and wildlife chased water around all summer long.”

Bird life

Adriana Stimax, education program director for San Juan Mountains Association, has kept a meticulous log of the birds that pass by her home near Mancos for the past six years.

This year, however, she’s noticed certain bird species hang around longer than normal.

“It’s different this year, markedly so,” she said.

The broad tail hummingbird, for example, was spotted in the third week of November. Usually, Stimax said, the bird leaves the region in September, and at the latest, October.

The spotted towhee, too, usually bolts for warmer climates at the first sign of cold weather. But Stimax said the large sparrow was seen above 8,000 feet in elevation in early December.

Birds are usually in a mad dash to migrate north in the spring, competing for territory. But on the way back in the fall, there isn’t that sense of urgency, and when they fly south is largely weather dependent.

That’s why anyone with a keen eye likely saw droves of migrating birds recently after a cold snap hit the region, turning weather from pleasant fall conditions to the dead of winter in a matter of days.

Wildfire season

One thing several people interviewed for this story pointed out that exemplified the odd weather year was the Ice Fire west of Silverton, which started late in the season and burned at high elevation.

“It was out of the ordinary,” the Forest Service’s Ertl said.

Typically, the high country around Silverton sees its first dustings of snow in October.

But this year, it was bone dry and warmer than normal, setting up perfect conditions for a wildfire to start Oct. 19, burning at elevations ranging from 9,800 feet to 11,500 feet.

It was a rare occurrence: The last fire that had burned near the town of Silverton was 141 years ago when the Lime Creek Burn (also around 8,000 feet to 12,000 feet in elevation) scorched about 26,000 acres around Molas Pass.

“These fires tend to not occur frequently, and the incidents that occurred in such late season events are really curious,” Remke said.

But, in this case at least, there may be a silver lining. Remke said aspens, typically fire resistant, burned hotter than normal in the Ice Fire because they were shut down for the winter.

“This is likely to favor quite vigorous aspen sprouting up there,” he said.