Birds in Winter

It's 10 degrees this morning, and soon the birds will arrive at the feeders. It amazes me that birds, who weigh so little, can tough out the winter here in Wisconsin. How do they survive?

Some birds grow extra feathers to keep them warm, doubling the amount they have in summer. Chickadees have about 2,000 feathers in winter. Other birds roost together in cavities or nest boxes to share warmth. Fluffing out their feathers allows them to trap air between them, keeping them even warmer.

When it gets close to zero, you may notice birds holding their feet up in their feathers to warm them. The way their feet are designed also helps them stay warm. Warm arterial blood descending from the heart meets a network of veins carrying chilled blood up from the feet. They are so close to each other that some of the warmth passes into the veins to warm the returning blood, while the rest keeps the feet warm.

Birds also shiver a lot in the winter. Stan Tekiela, a Minnesota naturalist, writes that shivering helps them produce heat at five times their basal rate, allowing birds to maintain a normal body temperature of 106-109 degrees when the air temperature drops to 70 degrees below zero.

Other birds take more extreme measures. As the temperature drops, they allow their body temperature to fall 10-12 degrees and enter torpor, a state in which they lose consciousness and can survive a temperature difference of 100 degrees between their bodies and the air. Hummingbirds, who migrate south for the winter, enter torpor at night to survive the cold at higher elevations. When morning arrives, they start shivering to raise their body temperature, and regain consciousness.

Birds must find food quickly on cold mornings to replenish the fat they lost the night before, or they will die. You can help them by putting out high-fat foods such as black oil sunflower seeds and suet. Making sure they have accessible food is especially important in snowstorms and blizzards. If you can, use something to block the snow and create a haven where they can come and eat.


photo by Yuri Timofeyev

Crazy Conifers

Lyman Glacier & Tamaracks, a photo by Marshmallow on Flickr.

This weekend a steady wind has blown many of the leaves off the trees. With any luck, though, the tamarack trees I visit on my walk around the lake will hold on to their gorgeous yellow needles a while longer.

Tamaracks, otherwise known as larches, are fascinating trees. They are the only deciduous conifers: their needles turn color in the fall, then drop off. They prefer the colder regions of the earth, including some states that hug the Canadian border. They look gorgeous when masses of them turn color, but they are also beautiful planted as specimen trees in yards, as they are here in Wisconsin.

Larches are members of the pine family, which usually holds onto its needles so that they can keep photosynthesizing all winter, helping them survive. Deciduous trees must expend a lot of energy creating new leaves each year. They make next year's leaves in the summer and early fall, when there is plenty of sunshine to give them the energy to do so, then store them in buds over the winter.

So how can a tamarack afford to put out new needles each spring? They do it sparingly, for one thing. Instead of sprouting as many needles as an evergreen, they put out tufts of needles at intervals along their branches, and single ones along new growth. That way, the needles don't shade each other, and they can maximize the amount of sunshine on each one.

So keep your eye out for naked pine trees this winter. The incredibly soft, light green needles they will sprout next year are one of the most beautiful sights of spring.

Operation Migration

Whooping Cranes on 2010_4x6, a photo by Operation Migration on Flickr.

Every year about this time, Operation Migration gathers the young whooping cranes it has raised and departs on an epic journey: a 1,200-mile trip from central Wisconsin to the west coast of Florida.

The young cranes have never made the trip, so they must be shown the way. To this end, they have been trained to follow an ultralight aircraft as if it were their parent. The goal of the yearly flights is to establish a viable population of whooping cranes that use this eastern migration route. All other whooping cranes migrate between Aransas National Wildlife Refuge, TX and Canada's Wood Buffalo National Park.

Whooping cranes were in danger of extinction in the 1940's, when there were just 15 of them left. By 1999, it was estimated that there were over 180. Operation Migration was founded because it was imperative to establish a separate crane population in case disease or weather threatened the western one. By 2006, there were 60 whooping cranes in the eastern group. The cranes return to Wisconsin on their own the following spring.

Operation Migration maintains a daily field journal during the migration so you can see their progress. Check out their website, www.operationmigration.org, and their photo stream on Flickr for more on this grand experiment.

Via Flickr:
Brooke Pennypacker leading 9 of the 11 juvenile Whooping Cranes in the Class of 2010 from LaSalle to Livingston County, IL
Credit: Veronica Anderton

Why Did The Woolly Bear Cross the Road?

Woolly bears are probably our most recognized caterpillar. They're an inch and a half long and covered with quarter-inch bristles. They're black on each end and reddish-brown in the middle. This time of year, you often see them racing across roads, sometimes in such numbers that it seems they're on suicide missions. What are they doing?

Woolly bears are the larvae of the Isabella tiger moth, a nondescript small brown moth. They can eat pretty much anything, including dandelions and grass. So they're not looking for food. They're searching for a good place to spend the winter. Insects can survive the winter in many different forms. In paper wasps, for example, only the queen of each colony and the eggs she carries live through the winter. All of the other paper wasps die. Many moths spend the winter in cocoons.

Woolly bears hibernate as caterpillars, curled under leaf litter or in any other protected spot they can find, such as your garage. In spring, they'll wake up and start eating again for a little while before forming a cocoon and turning into a moth. Now is a great time to pick them up and take a closer look. They won't hurt you; they'll just curl up in your hand. While you're at it, maybe you can help them across.