North Woods Naturalist

Chel Anderson is a North Shore naturalist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome back, Chel.

Anderson: Hi!

Well, it’s already starting. Cold nights, warm days; that means the sugar maple sap is flowing.

Anderson: It does, and we can all look forward to the products to come. We have a lot of maple syrup producers here for our relatively small population, and so we have a lot of experts for you all to call upon to really talk about the whole maple syrup production end of things, so maybe we’ll talk about the mechanics of sap flow, because sap flow as happens in maples is not really very common. There are very few species that actually have the kind of sap flow that maples, sugar maples, red maples, have, and it maybe be something that people don’t have a lot of understanding.

So, I understand that birch does?

Anderson: Yeah, birch are another species that do up here, but they’re really the only two groups of species that really have this kind of sap flow.

Why is that?

Anderson: Well, why? That’s always a really big question that I’m not sure any of us can really answer. It’s to do with their evolution as species that has made them different from other tree species, but the mechanics that they have evolved to have that create a sap flow are quite interesting. First of all, a misconception to clear up to start with is that we all learned in grade school and biology that sap wood in the tree conducts the water from the roots up to the rest of the tree and that the nutrients, the carbohydrates and other nutrients that the photosynthesis creates is conducted by another set of tissue called the phloem into the tree, back to the roots and into other parts of the tree. Well, in the case of the maple, that isn’t exclusively true, and that’s why the sap of the maple is sweet, because at this time of year, it’s actually absorbing sugars that were created by the photosynthesis during the growing season and stored in the tree in the form of sugars, sucrose, and that’s being absorbed into the sap and being carried by the xylem, by the sap wood. So, it’s a little different from what is happening in most trees. So, like other trees, things flow in both directions, up and down, but in the case of trees that actually have a sap flow, like maples, something forms called positive pressure, suction and osmotic pressure. Those three things are the mechanical aspects of why sap flows out of your tap in a tree or out of a wound. Let’s say, a big branch has broken off of a tree in a winter storm or something, or a beaver cut a birch tree down in the fall and now in the spring all this sap is falling out.

I’ve seen red squirrels nibble on branch ends of maple trees and lick the sap.

Anderson: Exactly. Red squirrels: really smart.

They are going to take over the world. Red squirrels and cockroaches.

Anderson: Yes, and they’re so energetic besides.

Let me ask you. When you talk about sugars and storage of sugars, now, do those sugars help the tree do something besides just produce sap?

Anderson: Oh sure. They’re part of the nutrients that the tree, that the photosynthesis--

They’re using it?

Anderson: They are using it, but in the fall, as things slow down, the tree can’t use all of the nutrients, carbohydrates that are being created, so they end up being stored in the cells in the tree and the tree freezes up and nothing is happening, until we start getting the weather cycle that you just described, warm days and cold nights. And, with the warm days, when the tree warms up and the cells in the tree warm up, there is carbon dioxide within the cells of the sap wood that gets released out into the spaces between the cells. And there’s also carbon dioxide in the sap itself and as it thaws and becomes liquid some of that escapes into those intercellular spaces and that creates pressure inside the tree.

You talk to a lot of tree tappers, and there are good years and not-so-good years. Sometimes that might be related to the weather, but is it also related to what happens to the tree, like, in the fall? Are there things that can affect the amount of sugars stored quite apart from the weather?

Anderson: What makes for good years and bad years is probably primarily due to these weather patterns and the access of trees to a good source of moisture to replace the sap that flows during the course of a warm day. So, once the pressure builds up, then sap will flow out of your tap in the tree. As the cold night comes, if the night gets cold, then the carbon dioxide actually shrinks and contracts, because it’s cool, so it contracts in between the cells of the tree, and some of it is reabsorbed into the now-freezing sap and cooling sap. And, when that happens, that creates a suction that draws water from the roots up into the tree to fill—so it’s a suction effect that happens. Then, when it warms up the next day, then the sap will flow again. Well, if you didn’t have a good source of moisture, of water, to move up from the roots, maybe a year when we don’t have a really good snow cover, and so the roots are down in frozen ground for the most part, there isn’t as much access to ground water. Those would be years when having a really strong flow would be much more difficult to create on a daily basis, because there wouldn’t be that access to a good resupply of the water. And then, of course, if it doesn’t get cold at night, then you don’t get that suction created and sap can continue to flow during the night, but then, of course, there’s less and less pressure, because you aren’t replenishing in the way that suction replenishes the fluid aspect of the sap.

Good plan.

Anderson: Yeah, and we don’t have to do anything!

Chel Anderson, botanist and plant ecologist. Thanks for helping us understand maple sugar.

Anderson: You’re welcome.

Photo courtesy of Sébastien B. via Flickr.

Chel Anderson is a North Shore naturalist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel!

Anderson: Hi!

Well, one of the most common tracks we see in winter snow is the familiar snowshoe hare. So, what are they doing to get ready for spring?

Anderson: They are doing what everything’s doing still, right now, which is just trying to stay alive and that’s increasingly hard at this time of year if you’re a browser in particular. So, something that’s eating the woody vegetation in the case of wintertime. Lots of things are getting buried under the snow that otherwise would be available to you, and you’re eating right along and snowshoe hares don’t travel huge distances in the winter. They’re not, you know, covering huge areas, so they’re working through their available foods, which, at this time of year, like I said, includes, you know, woody vegetation, but not heavy woody vegetation. They can’t be, you know, eating great, big limbs of things, they have to work on small twigs, on buds, on the inner bark of branches of trees that might fall down, you know, in a windstorm or something, or in the case of willows, things like that, that don’t get real heavy branches or stems, they can clip those off and work on the inner bark of those. And, of course, they’ll also eat the needles of conifers, so they’re just trying to stay on top of making sure they get enough to eat and out of sight of predators, which also are on the steady lookout for prey and hares are a very important prey species for many critters: foxes, coyotes, fishers, bobcats, lynx, raptors, owls, goshawks and returning things, things that will be starting to come back early on as winter kind of starts to melt away, new things will be on the lookout for hares. So, hares spend a lot of time this time of year, and really at all times, just kind of resting during the day when they can stay of sight, find a secluded spot and hanging out there. And they’re primarily crepuscular and nocturnal, so they’re feeding mostly at night, and they generally stick to fairly regular routes and areas that they spend different parts of their day in.

My yard.

Anderson: Yeah, and that reminds me that I just feel like the dullest of observers this year, because they have been lots of tracks around where I frequent, you know, trails around our house, and I have yet to actually see a hare this year. And, I just can’t believe how dull-witted I must be to not have been able to pick one out this year.

I don’t know. Earlier in the year, I did see quite a few, but this winter I haven’t really seen that many. I’ve seen tracks, but I haven’t seen them actually.

Anderson: Well, as I said, they are mostly active in the dim light and darkness, so I guess that gives me a little bit of an excuse. But, one thing is that they’re probably aren’t as many around as it seems based on the tracks, because, again, hares are sticking into a fairly small area and they’re very well camouflaged. They do take quite awhile to fully molt and change color, so that’s why sometimes in the spring when the snow goes early we see hares that are looking really obvious because they’re still mostly white and the reverse in the fall. So, it takes about 10 weeks, I think, for the total molt to happen.

I tend to categorize hares, bunnies, and rabbits all together and I shouldn’t do that. These are snowshoe hares.

Anderson: It’s a common thing. These are snowshoe hares, so perfectly, marvelously adapted to our world here, because they have those incredibly long hind legs and huge feet that allow them to literally float on top of the snow. So, I don’t know if you stepped off the trails anywhere when the snow was at its deepest, but around our place it was about 40 inches deep. So, you know, without your own snowshoes of some kind of another, it was not much for good going out there. But, again, when the hare populations are large, they tend to show up, you know, a lot in the summer out eating in the herbaceous vegetation that grows along the roadsides, especially at night, again, because that’s when they’re most active. And, during the time when the first litters are being born, then, you know, there’s a sudden surge in the population.

When is that going to start?

Anderson: Yeah, well, they’ll start in the spring. Here, hares might have two litters over the course of the summer. They’re very prolific breeders. Hares tend to live only about a year, so they have to do a good job on the reproducing side in order to keep their numbers going. And they do have cyclic populations, the reasons for which are not all that well understood, but it’s kind of a 10-year cycle of peaks and valleys, and the predators that they feed have kind of a trailing cycle often that’s associated with the cycle that the hares have.

When you say they’ll start to have litters in spring is it in April? May?

Anderson: Oh, May. June. Yeah. And, I’m not sure where the cycle is supposedly right now. I’m pretty sure it’s not at peak right now, but I don’t know if it’s really down in the valley or if it’s somewhere in the middle. But, there may just be fewer around then there were, say, a few years ago. I’m not really sure, but it’s discouraging to me that I haven’t actually seen one, but I’m going to keep an eye out for them.

Chel Anderson, botanist and plant ecologist. Thanks for helping us understand snowshoe hares.

Anderson: You bet.

The smallest owl in our north woods is the saw whet. Even though it’s only eight inches tall, it’s quite common and often seen and heard in our conifer forests. WTIPs Jay Andersen spoke to local naturalist Chel Anderson about this attractive little owl.

Photo courtesy of Blake Matheson via Flickr.

Chel Anderson is a botanist and plant ecologist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel.

Anderson: Hello!

Well, lots of tracks in the snow, and I’ve noticed by the size some must be fox. What kind of foxes do we have here?

Anderson: Foxes. Yeah. Very cool animal. Very common around our area, and pretty much across the state; one of the most successful predators on earth. Very adaptable to many different habitats, which is kind of a common theme. You know, if something’s really common over a large area, then it’s usually because it’s been able to adapt to lots of different kinds of habitats, from woods and forests like we have here to urban areas. So, yeah, fox are very common in Minnesota, in this part of Minnesota.

But, you don’t see them that often, do you? Or is it just me?

Anderson: Actually, I think I see them pretty often. But, I think it’s just a matter of luck, you know, in terms of whether you happen to be traveling regularly in an area where a fox is spending a lot of time and having some success with, you know, searching for prey or near their den or they take up residence near you and you get to see them. I’m sure it’s more or less serendipity. It’s certainly not because I’m out there following them around, but, seeing a lot of evidence of them, of course, in the winter with the tracks, like you mentioned. Here, in this part of Minnesota, the fox that we have is the red fox. The other fox that occurs in Minnesota is the grey fox. We do not have them here, although the red fox has a variety of color phases, which mean that we may see fox which are not the pure, beautiful, rusty red that we think of with black ears and nose and legs and a white tip on its tail. We might see the silver fox, which is more grey and black. There is also a color phase of the red fox that might be all black. Or the cross fox is another color phase which is red with dark bands across the back and the shoulders.

When you talk about phase, I often think of phase as a phase that the animal goes through. Is that true or is this a permanent state?

Anderson: No, it’s a permanent state. Color phase means just that within the genetic variability of the colors of the species, you can get these mixes. Just like in our wolf population. Not all wolves are exactly the same color. But, in the fox they’ve really defined these as color phases. The red fox that we have here stands about 15 inches or so at the shoulder. They’re about three feet long, including that just gorgeous fluffy red tail with a white tip, which is about 13 inches long or so, so a considerable amount of its length is that beautiful tail that’s flying out behind it when you see it scampering across the snow or across the road. You know, they weigh plus or minus 10 pounds. They are primarily hunting and moving around at night. They have fantastic night vision. In part, that’s because in addition to the light-sensitive cells of their eyes, behind that layer, they have another layer of cells that reflects light back through their eyes and really enhances their ability to spot their prey. They also have incredibly keen hearing. They can hear the rodents in the subnivian or rustling in the leaves in the summertime. In the summertime, they can actually apparently hear worms moving on the surface of the ground. Even though their classified as carnivores, they’re very omnivorous in their habits. So, you know, they eat rodents and catch a lot of prey, but they also eat berries and nuts and invertebrates. They’re not real fussy about what they eat.

OK, so they seem to be pretty good with everything, how about smell?

Anderson: Excellent sense of smell.

Might have known.

Anderson: Might of known. How else can you be a successful predator if you don’t have a good sense of smell? They also are very fast. They, for short distances, can run up to 30 miles an hour.

What are they after? Like, snowshoe hare?

Anderson: Sure, they’ll go after hares, red squirrels; they’ll dig down through the snow to get at things that are under the snow. When the snow isn’t, well, even now, when the snow is pretty deep, if you had a chance to watch them closely, you might see them listening closely and then pouncing down through the snow with all their legs come together and pounce down deep into the snow. They can leap up to 15 feet. So, if they hear something, you know, listen carefully and then determine within very close distances just how far that is away, they will leap to it and plow down through the snow and then dig furiously to get at it. This is the time of year when fox are breeding and mating, so in addition to being more visible because we can look for their tracks and maybe even see them out touring around, we might also have the best chance of hearing them. They make many different kinds of vocalizations and use them during the course of the year, but they’re most vocal during this breeding/mating time of year. The most common call is described best by I’m not sure what word, but some people like to say it’s a bark. It doesn’t really sound like a bark to me. Some people call it a scream. It seems more like some combination of that to me; it’s a barky scream.

Go for it, Chel. You’ve done this here before. You’ve given us an impression of animals before.

Anderson: Oh, I don’t think I could do it. It’s too weird. It’s too strange and I haven’t had a chance to just, you know, listen and soak it in enough to really feel like I could make it. To my ear, it also sometimes sounds like it ends almost with a short, little howl. So, it’s a “roooowwwrr.” Especially at night in February, March, these are the good times if you’re out, you know, we have some nice, mild nights this time of year, great time to go out and listen for all kinds of interesting sounds of the night.

Let’s set this record straight, now. Male fox, female fox. Give me the right names.

Anderson: OK, well, female fox are called vixens, and my understanding is that male fox are called dogs.

If the male and females are mating in February-March, when do we expect to have little foxes?

Anderson: Well, the gestation period for foxes is just over 50 days, I believe. So, you know, it could be anywhere from April sometime into May. They’d be born down in the den and be in the den for awhile before they’d be able to come up to the surface so to speak and move around. Then, you know, they hang out and play around the mouth of the den.

Like any canine.

Anderson: Like any canine.

Chel Anderson, botanist and plant ecologist. Thanks for helping us understand foxes.

Anderson: You’re welcome.

Photo courtesy of Ray Chang via Wikimedia.

Chel Anderson is a botanist and plant ecologist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel.

Anderson: Hi!

Well, a couple of weeks ago, some volunteers jumped into Lake Superior to help raise money for a charity. Yes, they did. They got out right away, leaving unanswered the question of what’s going on in the dark below the ice in our frozen lakes. So, tell me, what’s going on under the ice?

Anderson: It is cold in the water these days. Not as cold as the air temperature, though, right? At least most of the days recently. It’s not only cold, cool to cold, down there, but it’s also very dark, because, right, all the light from the sun, for the most part, is bouncing back into the sky and so, it’s pretty darn dark down there. But, it’s not all quiet down there. Things are still moving around. When fetching water from the water hole at our place, it’s not at all uncommon for us to see diving beetles moving around, giant water bugs have been at the water hole, dragonfly nymphs are being their whiz-bang predators that they are; all that is going on. Water scorpions have shown up at the water hole. So, lots of, you know, life is happening. It’s happening at a slower pace, but things are going on. Not just aquatic insect life, but also small mammals, like water shrews and star-nosed moles. They spend a lot of time, this is where they do most of their feeding, is in the water. One of the key things that’s going on, though, right now under water is that because the lakes are sealed tight with ice, the oxygen that the lakes went under the ice with is slowly being consumed by all the things that live there, except the plants, which normally take in carbon dioxide and give off oxygen, adding to the oxygen, but they’re not doing that, because there’s no light. So, the lakes have this kind of total budget of oxygen that’s there and until the ice leaves, that’s what everything has to live on. So, it’s being consumed, it’s not being created, so that, over the span of the winter, begins to have an effect on the life there. One of the really interesting ways to actually see the impact of oxygen changing over the course of the winter is to look at a little zooplankton that are called Daphnia—that’s the genus that they’re a part of—and they are planktonic crustaceans. They’re also called water fleas, but I’m not going to call them that, because they’re not fleas.

There have been some reports in the news lately about Daphnia as having a genome.

Anderson: Yeah, bigger than anything. Yeah, right.

Bigger than anything, and they’re hardly big enough to see.

Anderson: Yeah, right. Exactly. Yeah, good, I’m glad you brought that up. It’s very fascinating that this tiny little thing—so think, when I’m talking tiny, I’m talking the size of an apostrophe on your keyboard. So, these are tiny, but they are visible. You can actually see them.

And we have them here.

Anderson: And we have them. They’re ubiquitous in all freshwater ecosystems. They have tree-like tentacle arms that they flail over the tops of their heads which sends them spinning in kind of backwards circle, which seems kind of silly, except for it also drives water through their outer shells. Then, the filter algae, which is what they eat, and oxygen out of the water that passes through them. So, that’s why they do all this flailing. But, they have this amazing ability that is probably part of this huge genome that they have that’s given them the capacity to adapt to the really dramatically-shifting conditions that occur in their aquatic habitats, which can range from lots of water at one time of the year to no water sometime else, but also to changes in oxygen levels. The adaptation that they have that relates to oxygen is that they can make hemoglobin. So, during the summer when there’s lots of oxygen, they are translucent. But, during the winter or any other time when oxygen begins to be depleted, they begin to make hemoglobin for themselves so that they can survive in the depleted oxygen condition.

What does the hemoglobin do?

Anderson: Hemoglobin is the best way to move oxygen from a source of oxygen to where it’s needed that any life form can make. So, it’s the thing that makes our blood red, it’s the thing that moves oxygen from our lungs to the rest of our body, to our organs, to our muscles in our bloodstream. So, they are making this for the same purpose, because, in the summer when there’s lots of oxygen, it’s just moving right through them, there’s plenty of it. They don’t need any special mechanism to bring oxygen from water into their systems to use. Once the oxygen starts to get depleted in the water, then they need hemoglobin to do that transfer more effectively and efficiently. So, because they’re making hemoglobin, as the winter goes on and the dissolved oxygen in the water becomes diminished, they begin turn color, because the hemoglobin they make is red, too. So, as the oxygen becomes lower, they get pink, and when it gets really low, then they are red. And, how long the ice lasts has a big impact on how quickly that oxygen begins to be replenished. If the ice lasts way, way late into the spring, well, of course the oxygen then gets even lower in the lakes and ponds than it does if the ice goes off early.

Before we end the discussion, I know we agreed we’re not going to talk about fish, because we talk in all other sets of circumstances, but do fish slow down in the winter?

Anderson: Yes, fish slow down. I read some great descriptions of the people diving under the ice and actually approaching groups of sunfish that are just totally still, barely moving in the water. They were described as like autumn leaves suspended in the water, and as the person went by them or dove through them, they could just move their hand to part them like you’d part leaves on the ground, and they’d just kind of shift over, not moving on their own, but just moving because the diver was moving the water to push them aside. But, yeah, they’re just conserving, conserving, conserving so that they’re just sipping, sipping oxygen so that they can make it through.

That explains my luck ice fishing. Chel Anderson, botanist and plant ecologist, thanks for helping us understand what’s going on under the ice.

Anderson: You’re welcome.

Photo courtesy of Brynn via wikimedia.

Chel Anderson is a botanist and plant ecologist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel.

Anderson: Hi!

Well, even though it seems calm and serene in the winter woods, I know there’s stuff happening. So, let’s run down the list of who’s doing what now in the woods.

Anderson: Ok, yeah. Things that kind of give us—both seen and unseen—that give us a sense of where we are in terms of the winter season. So, one thing that tells us that we’re into the January-February sort of period is that the birch trees, the alder shrubs, the spruce and the balsam trees, their seeds are coming down out of their little cones and fruits. And this is a perfect time of year to try to learn about the shapes and start to identify those seeds, because they’re really visible on the surface of the snow in between snow storms and they’re not all coming down at once. So, the visible numbers are being replenished regularly in between the snowfalls. So, that’s one thing that’s going on and those are being noticed and enjoyed by many of our local birds, including, for me, the first group of redpolls that I’ve seen. Also, I personally had a recent observation of snow buntings still around. And I know they appeared on the Christmas bird count, but there are apparently some still around. Of course, they’re birds of the arctic the rest of the year and they’re going to spend time in the winter wherever they can find some open areas or places with seed sources available on the ground, specifically. I’ve never heard of anyone seeing one at a bird feeder, but that doesn’t mean it couldn’t happen I guess. I also heard a report of a cardinal. This was local to town area, so if you’re in town, keep your eyes open. Maybe you’ll see it, too. Also, it’s worth mentioning that all over the North Country now the bear cubs have been born. They typically come in at about 12 ounces. So, now they’re eating madly and sleeping a lot and, courtesy of their mothers, they’re bulking up, heading for that hoped for 10 pounds by April. So, you know, we wish them well.

I’ve seen a number of shrews lately, I haven’t seen them earlier in the year, but I found that kind of interesting because of the amount of snow, but I’ve seen them on top of the snow, I’ve seen burrow trails, as we’ve talked about. So, are the mammals starting to think about having babies now, too?

Anderson: Well, I wouldn’t think so, yet, but they’re probably doing whatever they need to do in terms of coming out of the subnivian in order to keep eating. All these small rodents, it’s all about keep eating, because they’re not spending any time dormant. They’ve just got to keep eating to keep alive, you know, furnaces running. So, if they’re having trouble finding enough to eat down in the subnivian, then they’re going to come out and go somewhere else. And in terms of other indications of the season, tree wells are also something that, pick out a few different trees that get sunlight, direct sunlight, during the day around the trunks where they meet the snow and start watching the tree wells really start to form now more significantly at this time of year. Because, the difference in what heat the tree trunks absorb versus the snow absorbs means that it’s quite a bit warmer at those tree trunks and so they start to create that little depression around the base of the tree.

Now, is that because our days are getting noticeably longer? Is the sun out more? Is that what causes the tree well?

Anderson: That’s partly it, but even more so it’s the angle of the sun. So, the angle of the sun is getting higher, so there’s really more energy reaching here, even though it might not seem like that everyday, but that’s what’s going on. Trees that have a darker-colored bowl for one reason or another, of course, their wells are going to be created faster than those that have a really pale color, because they’re absorbing more heat.

Yeah, they’re absorbing the heat, and then along with that additional angle, I can see what you’re talking about.

Anderson: Speaking of depressions in the snow, this is also a great time to be checking out possible locations where grouse have sheltered in the snow over night. And, as many of our listeners may already know, grouse use the snow as a place to both get some insulation from the cold overnight, but also to be out of sight of predators. They have this amazing routine of diving, literally diving, into the snow and I have to think that earlier on this winter that crust that we had that was, you know, a half-inch or more thick must have been a little bit of, I don’t know, a disincentive. I don’t know how they handled that, because I did see some, definitely saw some earlier in the winter, but, boy, it would seem like it would be kind of dangerous to be plowing in. But, now we have enough light snow on top of that that there’s room there. And so, they dive in, literally dive into the snow, and then they kind of push and tunnel forward from where they end up and they push the snow out behind them, to close the door, so to speak, on their little shelter. Then they kind of fluff out and push the snow around to make it a little bit more of a cave and that’s where they spend the night. When they’re ready to leave, then they just push themselves up and out or sometimes they burst out, sometimes from underneath your snowshoe. I don’t know if you’ve ever had that experience.

One time.

Anderson: Oh, great. Yeah, well, it’s definitely a heart-attack moment.

Well, he wasn’t that close, but he did take off and I figured “What is that?!”

Chel Anderson, botanist and plant ecologist. Thanks for helping us understand the seen and unseen in the winter woods.

Anderson: Always fun.

Photo courtesy of aka_lusi via Flickr

Chel Anderson is a botanist and plant ecologist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome back, Chel.

Anderson: Hi!

Well, this is the time of year when we start to speculate about how much ice there will be on Lake Superior. So, let’s talk about this and the impact that big lake ice has.

Anderson: With pleasure. I don’t know why, but ice on Lake Superior is incredibly exciting to me. So, I hope this isn’t overboard for those who aren’t that excited about winter in general, but I’ve lived here quite awhile now. I came up here in 1974 and, you know, during that time, we pretty much always have some ice on the shore by this time of the winter, but it’s really a fairly uncommon phenomenon on the lake, since I’ve been here, anyway, to have actual ice out on the open lake that makes it look like it’s iced over or, really rare, to have the lake actually freeze over. As we’ve talked about on a number of occasions, Lake Superior is a big heat sink. It absorbs warmth all during the spring, summer and fall and it does warm up, even though it’s not what we would call super swimmable most of the time. Because it’s such a huge mass of water, even if it’s only getting up to 40 degrees or 50 degrees in places, it takes a very long time for that heat to dissipate and get the water down to the point where it’s cold enough to freeze. So, this is a long process. So, it happens, ice forms out on the open lake and even in protected areas of Lake Superior much later than it does on our inland lakes. As we’ve talked also before, water out on Lake Superior, as everywhere else, as it cools down, when it gets to that 39 degree temperature, the water sinks into warmer water below, it’s replaced by warmer water, so that process has to go on and on and on until everything has cooled down to 39 degrees and the water is no longer sinking and being replaced by warmer water. And at that point, then the water at the surface can begin to go lower and actually get close to freezing and as that happens, and it can happen at different places and different times, because Lake Superior has shallow, more protected bays and those are going to be the first places that ice on the open lake is going to form. So, examples of that besides our harbor would be down by Duluth, up at Grand Portage bay, Thunder Bay. Those are places where you have big, shallow bays that are going to be some of the first places where ice will form on the open part of the lake. Then, elsewhere, once the surface water is actually staying colder than 39 degrees, wind becomes a huge factor in whether an ice sheet actually forms. So, the water can be down at 32 or even lower, but if we’ve got wind going on and it’s jostling it and moving it and creating waves and turbulence, just like a river, it’s not going to freeze into a sheet.

The lake is big, but it’s not affected, it does not have tides, but what is that phenomenon and does that keep the lake from freezing?

Anderson: Lake Superior does have a seiche and that can be affected by differences in barometric pressure over the different parts of the lake and it’s just a movement of water and certainly if there’s ice trying to be formed but you have any kind of an undulation, if it’s enough of an undulation, it’s going to prevent creating a sheet.

Well, I’ve been up here a couple of decades and in that period of time I’ve noticed there have been some flyovers of the lake. But, I can only remember a couple of times that it was reported that the lake was actually frozen over. What does it take to do that and does it freeze thick?

Anderson: Yes, it’s been very rare for the lake to completely freeze over, and, of course, we know it not by our own empirical experience, we can’t get up on a ridge and tell, but there’s satellite imagery that’s been available for decades now and you can actually go on the web and look at NOA’s Great Lakes Ice Atlas and you can actually look at charts of winters from the 1970s up until 2003 where they’ve taken those images and they’ve then made a chart that shows the great lakes and shows the maximum ice cover for a given year. So, the ice is going to be variable in thickness, even in a year like that. But, it’s going to have a lot of areas with very thick ice, because in order to be durable out on the open lake, ice has to be thick. Once an ice sheet forms out from our shore here, whether it survives very long or not is really dependent on the weather right then. Our ice usually forms on a cold, still night. Even if we don’t get those sheets of ice that last very long, even just having the ice form and then be moved around by the waves creates all this interesting dimension to the shoreline that we don’t see at other times of the year.

There’s a phenomenon that I’ve noticed that doesn’t seem to be too related to waves, but just in the general motion of the lake, when ice that’s, you know, less than an inch or maybe an inch, at the most, thick, starts to move into shore and slide up over itself and creates an incredible sounds and it’s an amazing experience.

Anderson: I agree totally. It’s just an incredibly inspiring and intriguing phenomenon. Both the sounds, as you say, if it’s really thin ice and it’s just starting to break up, it has this really light—what’s the name of that instrument that has the—the glockenspiel! It has that tone, just this beautiful light, clear tone, of small, bright sounds that come out of the ice. But, if it’s a thick sheet of ice that’s either formed on our shore or formed somewhere else and blown over here, but if one forms here or elsewhere and it comes to our shore when it can be pushed along by the wind and actually grind its way, both either right up, like you’re talking about, on to the shore or along the shore, but they’re grinding away on the bedrock as they go, and that’s a really good example of how lake ice plays a huge role as a disturbance factor on our bedrock shores.

Is there any difference in the character or quality of the ice on this side of Lake Superior as opposed to the other side?

Anderson: Big sheets of ice form more frequently and earlier in the year in other parts of the lake where the character of the lake is generally shallower. That’s why often the first ice sheets we see come from someplace else on the lake, could be the south shore, might be the east side of the lake, where there are big areas that are shallower and they can be very thick when they get here and they come ramming up on the shore.

Chel Anderson, botanist and plant ecologist. Thanks again for helping us understand this time what’s going on with ice on the big lake.

Anderson: Always a pleasure.

Chel Anderson is a botanist and plant ecologist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome back, Chel.

Anderson: Hello!

Well, we have, from time to time, talked about how birds cope under various circumstances. We’ve had sub-zero cold, wind and snow so far, so how do birds adapt to this severe weather?

Anderson: Great question. And, we could ask ourselves, how do we adapt?

Sometimes I do.

Anderson: Because it would give us some clues as to how birds adapt, but they do have some extra-special adaptations that are worth remarking on for sure, because they really are amazing in some ways. Birds have actually a lot of resistance to cold, and the obvious one, of course, is their nice, down coat. And we’ve talked before about how they can fluff those up, put air up in among their feathers just like you fluff up your down comforter when the night is going to be particularly cold and they do that and over the course of the day watching at your bird feeder or if you can watch a bird in the woods for the day or a good part of the day and the weather changes and you’ll see the bird change. You’ll see it looking really poufy, Michelin Man sort of style of figure, you know, early in the morning or when the temperatures are coldest and then as temperatures moderate during the day, you won’t see them looking like that so much. If they stop and rest for awhile in one place, then you might see them eventually kind of fluff out again to regulate their temperature, but that’s definitely a key thing, but it’s not all. We’ve also talked about how they eat high-energy food. They’re going after the highest energy food that they are adapted to eat and that they can find, and that’s because they need that energy-rich food to keep their high metabolism in full swing.

I was just going to ask about their metabolism. Do you also happen to know anything about body temperature?

Anderson: I can’t tell you exactly what body temperature any given bird is, but it’s much higher than our temperature, and importantly, in terms of this high metabolism, they have about two times the glucose level in their blood as we do. So, that’s how they keep that furnace going.

Song birds are pretty small, most of them. What song birds can tolerate cold the most?

Anderson: Well, from what I understand, common and hoary redpolls, which we do see her some years, maybe most years even if we’re lucky. They apparently have the highest cold tolerance of any songbird and apparently one of the ways, along with the ways that we’ve already talked about, they have a specially adapted pouch, either kind of part of or near their esophagus and they can actually fill that with food as it gets close to nighttime. Birch seeds would be a good example. They would focus on feeding on those in the latter part of the day especially, and they can stash a lot of those seeds in that pouch and then use that during the night to help them maintain their furnaces, to help them going strong. Other birds like Evening Grosbeaks and some other northern finches have a crop and they can store seeds in their crop and use those to help them maintain overnight. But, apparently, redpolls have set the record in terms of maintaining overnight. But, most birds utilize other adaptations to protect themselves overnight besides those that have the opportunity to cache some food internally and use it. Some birds, temporarily, when they’re at rest at night or other times of the day in response to cold might shiver. OK, shivering is a way to boost your heat. But, of course, you can’t do that indefinitely, because it takes energy to do it. But, that’s a temporary relief from cold that a lot of birds will use when they’re at rest and at other times of the day. Small birds are at a disadvantage compared to large birds because their surface to mass ratio is greater. So, they have an adaptation of having more feathers per unit of bodyweight that helps them compensate some for that disadvantage that they have. Redpolls have one particular special adaptations, the finches have another, jays have yet another. So, there are multiple ways that these issues of how do you maintain your body temperature overnight in particular that birds have evolved to do that.

Well, one more thing. What can we do as bird feeders, what’s the best thing to do to help them have this high-energy food that they need this time of year?

Anderson: Well, right, focus on the highest energy, putting out high-energy food. So, the oft-repeated thing is that suet, whether you make your own or buy it is really great, anything with a lot of fat in it can be suet, it doesn’t have to be animal fat. So, some people make up suet balls that incorporate peanut butter and things like that. So, high fat. Obviously, seeds that have the highest fat content, so black oil sunflower seeds are kind of a seed that many species can eat and are very high in fat, so that’s a good choice.

I’ve never seen redpolls at suet feeders. Am I just not seeing that or don’t they generally do that?

Anderson: Finches are not going to show up at suet feeders. The birds that are going to show up at your suet feeder are the ones with the pointy, narrower beaks, because they’re the ones that are going to be able to get that, scrap it off and peck it out. Finches are really all about seeds and fruit when it comes to food. And, of course, insects, when they’re feeding, trying to feed their young. But, in the winter, they’re going to be about seeds and fruit. But, if you’ve been feeding birds, started early and are feeding birds right along, you’re very-local-to-your-home-place birds are becoming somewhat reliant on that food. So, if you’re going to be gone, you need to either have someone stocking your feeders or you need to slowly wean your birds off the amount of food that you’re putting out because they’re not anticipating that that’s just going to disappear.

Chel Anderson, botanist and plant ecologist. Thanks for helping us understand birds in winter.

Anderson: You’re very welcome.

Chel Anderson is a botanist and plant ecologist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel.

Anderson: Hi!

Well, they’re white and pretty ferocious hunters. So, tell us about least weasels.

Anderson: OK. Will do. Least weasels. Let’s start out with some basic things about weasels, because it’s easy to get them confused, I think. We have a group of little weasels, and the least weasel is, of course, the smallest followed by the next largest, which is the ermine. They are different. Some people confuse them. And then, the next largest—so the largest of the weasels—is the long-tailed weasel. So, we’re going to talk about the least weasel, which, as you say, is a very notoriously ferocious and feisty predator of the woods and meadows and fields of a fairly large range of North America. We’re kind of in the southern half of its range, so it goes all the way up into the arctic. So, it’s a pretty successful little carnivore, but a hard one to get a look at because they’re quick, they’re small, they’re really busy because they are hunting pretty much 90 percent of their lives, which are pretty short. They live about a year, is all. So, it’s a fast- and furious-paced life for a least weasel. Least weasels are 6.5 to 8.5 inches long and about a quarter of that is the length of their little, short tail. So, these are really small creatures. Sleek, long and sleek, and chocolate brown on the back and tail in the summer and white on the chest and belly in the summer. Then, turning all white like the ermine in the winter.

Do all weasels turn white?

Anderson: No, the long-tailed weasel does not turn white. The ermine and the least weasel do. The key distinguishing feature—both summer and winter, but especially obvious in the winter between the least weasel and the ermine—is that the ermine has a black tip on its short tail. The least weasel does not have a black tip.

Well, how do these guys survive in the winter?

Anderson: Yeah, well, the least weasel is eating between a third and a half of its body weight every day. So, think about trying to do that yourself.

No, I’d really rather not think about doing that. I wouldn’t be able to get in the studio.

Anderson: No, but it would take a lot of time, right? Even though getting food is a little bit easier for us, you know, even if you have to go somewhere and go shopping for it and prepare it. It’s still fairly easy. But, if you have to hunt for your food, this is a big endeavor to eat that much of yourself. A least weasel weighs one to maybe 2.5 ounces, so this is less than you can mail with a first-class stamp. So, they are small, but still, eating half your body weight is going to suck up a lot of time and they pack a lot of energy and feistiness in that little package that they are. This time of year, they are spending a lot of time searching, and they use kind of random search pattern for their hunting method. And they are checking out every little tunnel down into the snow, every little tree well that will eventually develop. They are using both visual, auditory and scent clues to know whether they should explore further when they poke, you know, their heads down a dark hole. And, of course, they’re small enough to be able to go down into that subnivian layer and move around down there. Even though, of course, it’s going to be quite dim, they’re going to be able to move around and search for their prey in that subnivian layer and take advantage of those better temperature conditions. Because, remember, like all of our critters, they’re living in this energy budget world in the winter and they need to be able to sustain their body temperature in the face of the cold, so if they can get down and spend some time in the subnivian and have it pay off in terms of finding some food, then you’re having a better chance of sticking within that energy budget.

What are they going to find down there?

Anderson: Well, their big items are going to be rodents of all kinds—mice, shrews, voles. They might even find the occasional insect that’s dormant, and they would eat those, and in the summer, they eat insects as well as if they happen into ground-nesting birds, small ground-nesting birds, they would definitely take advantage of those options. They’re very efficient and effective predators. They are ferocious as you said, in the face of especially something—another animal, including a person—trying to take away a kill, they will go on the offensive against much larger animals in defense of a kill that they’ve made. But, because of their size and, of course, because they are important players in the lower part of the food chain, they’re a great meal themselves, so they are actively hunted by larger mammals, fox, even larger weasels like the ermine or the long-tailed weasel. House cats, even, have been known to take least weasels, and then raptors, of course-- owls and goshawks. If you want to try to see evidence of them, because they’re really hard to see in the summertime, as a lot of our other smaller animals, winter is a good time to try to pick out their tracks from among the variety of tracks that are out there. So, if you want to try to check that out, recall that weasels are bounders, so you’re looking for pairs or small clumps of tracks that are separated by long leaps. And, in the case of the least weasel, we’re talking about the leaps that aren’t maybe more than 8 inches, and that would probably be the outside. And, they’re going to have very tiny groups of tracks because their feet are only about a half an inch in length and width. These are weasels that might leave a bit of a body drag because they have such short little legs, if the snow is really light and fluffy, they’re going to go down. You know, you might be lucky enough to spot one zooming across the surface of the white snow. But, if it has a black tip, don’t be misled.

So, that’s the most we can say about the least.

Anderson: Perfect.

Chel Anderson, botanist and plant ecologist. Thanks for helping us understand what’s going on with least weasels this winter.

Anderson: You’re welcome.

Chel Anderson is a botanist and plant ecologist. She lives in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel.

Anderson: Hi, Jay.

Well, it is the dead of winter, as they say. Time to check in with our four-legged friends: deer. How are the deer doing?

Anderson: Yeah, well, deer are definitely among us. I think we’re all very aware of deer and they’re one of those creatures of our landscape that are so beautiful and so graceful and really a wonder to behold. But, they also pose some challenges to us because of some of their behaviors related to winter. So, let’s talk about the deer and why they do what they do and how they sometimes end up crossing paths with us in ways we would prefer they didn’t. To start with, the Whitetail deer is one of the most successful mammals on earth. It has a range from southern Canada to South America. So, this is a very successful animal. It has learned to adapt to an amazing array of environmental conditions and habitats and including urban habitats, right? So, it’s really not that far afield to say deer are everywhere, you know, except the driest deserts and the most, totally inhospitable places.

Yeah, they hold deer hunts in Duluth, in the city.

Anderson: Yeah, in the city. So, deer are really amazing animals, but like all animals that stay through our winter, they have to be able to survive the rigors of winter which basically come down to an animal has to be able to live within an energy budget, and the energy budget consists of the fuel you can consume, find and consume, and the energy it takes to move around and get it and to avoid predators. They need to be able to deal with the temperatures. They also need to be able to deal with the depth of the snow, and they have to have food; those three things. For deer, good food resources are basically woody vegetation; shrubs, small trees, that’s what they are surviving on. So, they need to have an adequate amount of that wherever they are spending the winter. Then, for temperature, they come equipped with a wonderful fur coat. And, as anyone who spends the year here knows, they are a different color here in the winter than they are in the summer. So, the coat acts both as a camouflage, but also as a thermal regulatory device. And, in the summer, we have that nice, reddish coat that is very thin that allows the deer to reduce heat stress. Then, in the fall, that color begins to change, begins to lighten up to grey-brown, and that’s as the winter coat comes on and the molt happens and the guard hairs grown out about two inches long, these very fluffy guard hairs that come out and then underneath that is a very dense, dense layer of shorter hairs. And the combination of those guard hairs trapping air between the outside and that underlayer of hair and then the density of that fine layer underneath, that is a tremendous insulator. So, deer, moose as well, you see them walking around the woods sometimes with this blanket of snow on their backs, because they are so well-insulated, that heat-trapping device of their fur coat is really, really excellent at keeping them warm.

Deer yard, what is that and why?

Anderson: Yeah, let’s talk about that. So, we talked about how temperature is an important thing; they have to be able to regulate for, and they have their coat. But, the coat alone isn’t necessarily going to work when it’s 40 below and the wind is blowing 30 miles an hour. So, deer definitely take advantage of thermal cover. We’ve mentioned this before, too. So, thermal cover is a place where there are coniferous trees growing—hopefully in a group, but even just one will make a difference—and with branches that come down close to the ground. So, this is primarily balsam fir, spruces, and cedars, or young conifers of other kinds, but the branches have to be down closer to the ground, not towering way up high. That keeps the air from moving away from the ground so quickly. So, it holds—I mean, it sounds silly. I mean, thermal cover when it’s 30 below? But, it does make a difference how quickly the heat moves away from you, as the animal, and the ground. So, those needles help slow down that movement of air and they can also act as a windbreak. So, if you’re a smart deer, you’re going to find a place out of the wind, could be in a grove of conifers, might be behind a ridge, you know, where the landform creates a block to the north wind or whatever the direction of the wind. And they also then can find themselves leaving behind what is a solitary and widely-space life during the summer as either box-isolated male deer or small family groups of does and their fawns. That kind of falls apart during the winter, because the deer tend to go to these places that offer them the best shelter. And, as the deer yard there, they pack down the snow, just from their movements they pack down the snow. So, then they start to improve the condition with respect to that other winter feature that we haven’t talked about yet which is snow depth, which might be the most critical factor for deer. Deer are very well-equipped to deal with our temperatures, but because they can’t grow longer legs, they can be very stressed by snows that surpass about 15 inches in depth, because they’re having to bound everywhere they go, otherwise they’re wading, and they can’t drag their legs through the snow particularly once any kind of a crust develops. And, if the snow gets to the point where it’s 20 inches, than even larger deer begin to drag their bellies and their chests, so think in terms of yourself being out without a trail in 24 inches of snow or more and how that feels like wading. I mean, the energy you expend to just go a short distance is huge. So, that’s when the energy expended to get to your food begins to exceed what you can gain from eating that. If you can, you move to places where there isn’t so much snow, maybe really packed down by deer in the yard, or in the case of where we live, we have one very huge deer yard, which is right here close to the lake. Because, close to the lake we have, typically, milder temperatures and we have lower snow totals. So, as the snow builds inland, they will begin to move down toward the shore. And, eventually, they, many of them, will spend the winter here, or much of the winter here, because of the factors that I just mentioned. That’s why it’s not just a figment of our imaginations that there are more deer by the shore in the wintertime than there are in the summer, because many of the deer that have lived the rest of the year inland have come down to the shore.

Chel Anderson, botanist and plant ecologist. Thanks for helping us understand what the deer are doing.

Anderson: You’re welcome, Jay.