Category Archives: Winter

The sub-nivean zone

Hi all! Happy New Year! I wish everyone joy, peace, and health in the upcoming year.


And now, to start things off with a bang, check out my most recent Earth Matters column in the Hampshire Gazette (Jan 2, 2016). It’s about life under the snow:

The Pond in Winter

Wow, what a warm winter it’s been! Although today is predicted for a high of 37 (F), as those of you who live in this area know, the temperature has been in the 50s for weeks – very warm for December in New England. Christmas is nearly upon us, but the lack of seasonally-appropriate weather seems to have robbed almost everyone I know of a sense of “Christmas spirit”. (At least, amongst those who celebrate Christmas.)

On the up side, the warmer weather means I have gotten to go outdoors at lunchtime and take photographs! I am by no means a professional photographer, but I’ve been experimenting with a loaner camera.  Not surprisingly, wildlife photos are proving to be very difficult (the lag time causes me to “lose” the subject, and focus can be a challenge), but here are some early efforts.


Mallard 121315
Male Mallard 12/14/15
Canada Goose 201415
Canada Goose 12/14/15
Black Ducks 121615
American Black Ducks 12/14/15

We also had this unexpected visitor: a red-necked grebe in winter plumage. It is unusual to see this bird on such a small body of water. It was a bit shy and stayed in the middle of the pond.

121415 red-necked grebe Umass Amherst pond copy
Red-necked Grebe 12/14/15

Photos aside, this warmer weather does not signify anything good about the condition of our planet. Here’s to colder temperatures in the days to come!

Owls in February

In recent days, we have been the ever-so-lucky recipients of an “arctic blast”, exceptionally cold air pulled down by the jetstream from more northern climes. The wind chill has been much worse than the actual temperature; it was supposed to be -31 a couple of nights ago. I personally did not confirm this, preferring to stay inside and watch another episode of “Bones”.

By William H. Majoros via Wikimedia Commons
By William H. Majoros via Wikimedia Commons

On the upside, in spite of the cold weather, nature presses on. Believe it or not, now is this time (in New England, anyway) when great horned owls should be nesting, skunks mating, and redpolls arriving from their southern homes. If the weather warms up tonight (which is predicted), I might go out walking through the snow, listening for great horned owls. This is what I will be listening for:

Of course, great horned owls aren’t the only owls you might hear at night. Cornell’s Ornithology Lab offers a download of a variety of owl calls that you might encounter.

And, for the real bird dorks among us (like me), here’s their livecam of a great horned owl’s nest in Savannah, Georgia. This is what we in New England have to look forward to in the upcoming months!

The nest, originally built by a pair of bald eagles, now contains the female and two baby owlets, hatched in early February. For video highlights dating back to mid-December, see here:

Happy owling!

Snow, snow, and more snow

"Novo mesto Breg 2". Licensed under CC BY-SA 3.0 via Wikimedia Commons
“Novo mesto Breg 2”. Licensed under CC BY-SA 3.0 via Wikimedia Commons

I am perhaps growing a little weary of the subject of snow, yet that is what there is this winter, in vast and ever increasing abundance. Snow, snow, and more snow. Lacking snow shoes, I wade through thigh-deep powder to the bird feeder, trying to keep up with the demands of little goldfinches, chickadees, and nuthatches. I sprinkle sunflower seeds under the feeder for the ground-feeding birds, knowing that, in fairly short order, those seeds will be covered up by yet more snow. I wonder how many of them get eaten, either from above by birds and squirrels, or from below by small rodents tunneling up from the sub-nivean world. Come spring, will I find a giant pile of soggy, uneaten seeds attempting to sprout? Several more months will pass before I’ll have an answer to that question.

In the meantime, some youthful part of me still gets excited by snow days. “What?? Snow day?? Everything’s closed!! No school!!” It’s been a while since I’ve been in school, but the excitement persists. In light of that feeling, here is fun poem by Billy Collins, entitled “Snow Day”.  Enjoy!

The sub-nivean zone

Well, the great blizzard of Ought Fifteen was a bit of an anti-climax here in my neck of the woods. Instead of the 27″-33″ that had been predicted, we got about 5″. I’m not complaining – the poor folks in Nantucket and Boston really got hammered – but rather am admitting to a mild feeling of let-down after all the water I bottled, the extra wood we sawed, and the emergency flashlights and candles I purchased. Ah well, at least we have another 5″ of snow, and, counter-intuitively, that actually makes for better winter conditions for our small wildlife friends, including moles, mice, voles (and their predators), various insects, and an assortment of bacteria and other microscopic life. This is because of the creation of the sub-nivean zone, which occurs after about 8″ of snow accumulation. (In case you are doing mental math, we had 3″ or 4″inches of previous snowfall, plus the additional 5″ish, leading to a total of 8″ or 9″.)

Entrance hole to the sub-nivean world. Photo by the Seney Natural History Association via Wikimedia Commons.
Entrance hole to the sub-nivean world. Photo by the Seney Natural History Association via Wikimedia Commons.

The sub-nivean zone (“sub”= under, “nivea” = snow) occurs in a protected area between the upper-level snow pack and the earth’s surface, where the temperature hovers around 32 degrees (F). The upper levels of snow provide insulation, while the lowest level melts slightly due to the heat from the earth’s surface, providing water and unfrozen food sources. Indeed, a whole winter ecosystem exists here, a fact that was not widely known until relatively recently. Rodents living in this zone create tunnels, air holes, latrines, and nesting areas, feeding on grasses, insect eggs, and whatever else they can find during the winter months.

The upper layers of snow hide rodents from the sight of predators, although owls can hear them running from 30 yards away, and foxes and coyotes can smell them. These predators will pounce through the snow, attempting to catch their prey with claws or mouth. You have no doubt seen videos such as this one, of a fox leaping into the air to try to pin a rodent through the snow:

(As a side note, according to the Discovery Channel, new research shows that if a fox is facing north (at least in North America), he/she is 75% more likely to be successful in catching prey through the snow than if facing any other direction. The reason for this is not fully understood.)

Weasels, more sneakily, slide down the rodents’ air tunnels and chase their victims through their own homes. (Don’t feel too bad for the little critters, though; if it weren’t for predators like weasels, our world would shortly be overrun with mice, voles, and other rodents, given how fast they tend to breed.)

Next time you are out walking in deepish snow, keep an eye out for traces of predators, such as fox jumps or owl/hawk punches. (In the photo below, note the marks left by the wing feathers and the hole punched through the snow by the bird’s feet.

bird wing snow
Photo by U.S. Fish and Wildlife Service via Wikimedia Commons:

Alternatively, look near the base of trees or rocks for air holes leading to the sub-nivean world. (Please don’t disturb the holes, however; the creatures that made them have enough to contend with without our interference.)

For more information on the sub-nivean zone, see here:

or here:

Winter survival

Hi all! Great to be back after a little hiatus.

Given the weirdly fluctuating outdoor temperatures so far this year, I have been contemplating the myriad of ways in which animals survive the winter. In pursuit of more knowledge, I pulled Bernd Heinrich’s Winter World: The Ingenuity of Animal Survival off of the shelf, and, even though I am only a couple of chapters into it so far, have already learned several interesting tidbits.

Snow fleas (Hypogastrura nivicolautilize) utilize anti-freeze to stay alive in the snow. Photo by Daniel Tompkins via Wikimedia Commons
Snow fleas (Hypogastrura nivicolautilize) utilize anti-freeze to stay alive in the snow. Photo by Daniel Tompkins via Wikimedia Commons.

For instance, some insects survive winter because their bodies contain substances, similar to antifreeze, that lower the freezing point of water. (As a side note, some types of deep water fish contain a similar type of “antifreeze”, the gene for which is now being used to prevent ice cream from getting freezer burn. Yoiks!)

Even more astonishing than having antifreeze-filled bodies is the fact that some insects have the ability to separate the freezing and melting points of water (!!) in a process called “thermal hysteresis”. Think about that for a minute: generally, the temperature at which water goes from a solid state (ice) to a liquid state (water) is 0 degrees Celsius/32 degrees Fahrenheit. However, the process of thermal hysteresis allows these insects to exist in a “supercooled” state (below 0 degrees C but without freezing) and thus survive cold winter temperatures without dying. This supercooled state, however, is highly unstable, and the introduction of any foreign molecule will cause the entire system to break down and freeze almost instantly. Life is so amazing, and so fragile!

Additionally, some insects can utilize a process called “diapause”, which could be loosely defined as a type of “arrested development”. Many moths, for instance, live as pupae through the winter in a diapausal state.  (A common example is the type of yellowish, fuzzy tent caterpillar cocoon that you sometimes find attached to the underside of a log in a woodpile.

by NobbiP via Wikimedia Commons
A woodpile is a great place to look for overwintering insects. Photo by NobbiP via Wikimedia Commons.

These pupae, which are waiting until spring to hatch into moths, are in a state of diapause. (Naturalist’s note: not all fuzzy, pale-colored cocoons are those of tent caterpillars; you may need to do further research if you wish to correctly identify any particular species.)

The phenomenon of diapause is not limited to winter months, however; some adult insects will enter a reproductive diapausal state in the summer when migrating or searching for host plants. In fact, some types of insects, in the adult phase, do not even have mouth parts, as they quickly breed and lay eggs before dying without eating anything at all. I am not sure if this evolutionary phenomenon counts as diapause or not; perhaps biologists refer to it as something else altogether.

By Stephen Lody via Wikimedia Commons
Adult polyphemous moths (Antheraea polyphemous) have only vestigal mouthparts. Photo by Stephen Lody via Wikimedia Commons.

Anyway, the next time you are outside this winter, check under logs, rocks, or dead leaves to see what kinds of insect life you can find, waiting until next spring to re-emerge. If you want to learn more about what kinds of creatures you are likely to discover, see here for what one biologist found in her woodpile in Ontario. (Note that the author of that blog is also a co-author of the new edition of the Peterson Field Guide to Moths of Northeastern North America Happy exploring!

To feed or not to feed?

In recent years, a controversy has sprung up around the time-honored and very popular tradition of backyard bird feeding. Once viewed as an unabashedly positive activity (“Look, I’m helping the birds!”), a couple of recent studies done in the U.K. have indicated that feeder-fed blue tits and great tits (relatives of the chickadee) laid fewer eggs, had lower hatching success, and ultimately fledged fewer chicks. (The question of “why?” was not answered.) It is important to note that these are only a few studies amongst many that have shown positive benefits. Other studies have shown the exact opposite impact: earlier laying dates, larger clutch size, and higher overall breeding success. A study of chickadees in Wisconsin showed a dramatically improved over-winter survival rate (69% for feeder-fed birds, vs. 37% for non-feeder-fed birds). (For more details, see here:

By Ano Lobb (Flickr: Black Capped Chickadee hovering at feeder) [CC BY 2.0 (], via Wikimedia Commons
By Ano Lobb (Flickr: Black Capped Chickadee hovering at feeder) [CC BY 2.0 (, via Wikimedia Commons
So, what’s a nature-lover to do? I tend to err on the “feed” rather than the “not-feed” side, given the preponderance of evidence – and, for better or for worse, the fact that I enjoy backyard birdwatching. I currently have only two feeders: a standard tube-type, which I fill with sunflower seeds, and a suet feeder. That’s not a lot of feeders, and the birds don’t come very often; only every few days, rather than all day, every day, as has been my prior experience. I suspect that a neighbor provides a better food supply, and the birds only come to my yard when that runs dry. Alas! If the ground wasn’t frozen, I might add some more feeders. In the interim, I am investigating a heated water supply, though this is probably unnecessary, as birds have long-since adapted to northern winter weather without such fancy, modern devices.

By Ted [CC BY-SA 2.0 (], via Wikimedia Commons
Photo by Ted [CC BY-SA 2.0 (, via Wikimedia Commons
For a brief but thorough and non-commercial summary of bird feeding tips, see Minnesota DNR’s page, here:

Happy birding!

Frigid morning

Woke up to a frigid morning. NOAA reported the temperature at -1 degrees (F) at 8:30 am, though my partner reported -4 in his car. Bad time to have run out of wood, though the oil is doing a surprisingly good job of fighting the bitter cold that presses against the walls and oozes though the windows. This house, though originally built in the 1840s, is much better insulated than our prior house, a 1790s drafty bucket with almost no insulation beyond some lovely double-paned windows. At almost 3K square feet, mostly closed off and unheated during the winter, we nonetheless went through 6-7 cords of wood a year. Yes, this new house is definitely an improvement.

A kind but strange neighbor generously donated a cord of wood to us not long after our arrival here this summer, but then spent several subsequent days staring longingly down our driveway. For a week or two, it seemed that he took daily walks by our house, hovering near the edge of the property like a hungry sparrow. I’m not sure he wanted the wood back so much as conversational opportunities, but his behavior was so odd that I took to staying in the house every time he came around, and finally he gave up. I felt a little guilty, but do not plan to be held hostage by anyone’s generosity, whatever the motivation. I hope he has found some friends.

Anyway, yes, it is frigid this morning. En route to collect the last, skinny maple logs, I found a number of tracks in the snow. What do you think they are? (The first 5 photos are all the same animal.)