Thursday, December 04, 2014

Whooping cranes spotted during stop in Champaign County

Whooping cranes spotted during stop in Champaign County

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Recently, my wife and I were out for an afternoon of birding at the Middle Fork River Forest Preserve in the northeast corner of Champaign County, when we came upon a pair of birds I’ll never forget. They were nearly five feet tall with long black legs and snowy white feathers, red caps, black masks and bright yellow eyes. Although I had never before seen them in person, I knew immediately they were whooping cranes.

Whooping cranes occur only in North America and they were apparently never very common. Their numbers plummeted through the nineteenth and twentieth centuries as a result of unregulated hunting and habitat destruction. At three points in the 1940s and 50s, the total population of whooping cranes dipped to 23 birds, with just 16 individuals in the only remaining wild flock at one time. Since then, some of the most intensive, coordinated species recovery efforts ever mounted have brought whooping cranes back from the brink--very slowly, and with plenty of bumps in the road.

The conspicuous banding on the pair of whooping cranes my wife and I observed indicates they are the result of one of these efforts, a collaboration among state, federal and nonprofit agencies called the Whooping Crane Eastern Partnership. The purpose of the partnership is to establish a self-sustaining migratory population of whooping cranes in eastern North America.

This is a critical addition to the wild population in the west, which breeds in northern Alberta and spends the winter in Texas near the Gulf of Mexico. That’s because a single disaster, such as a hurricane, could kill them all at once.

Chicks destined for the eastern migratory flock are hatched from eggs produced by captive breeding pairs and raised according to careful protocols to ensure they grow up understanding themselves to be whooping cranes, not people.

During their first year, some of these chicks participate in Operation Migration (OM). They learn to fly behind an ultralight aircraft, which then “teaches” them to migrate from their summer home in Wisconsin, to a National Wildlife Refuge in Florida where they spend the winter. The female of the pair we saw is a graduate of this program.

 [Photos by author. See biographies of the pair at these links: him 27-06 and her 26-09.]

Other chicks destined for the eastern flock are part of an experiment called Direct Autumn Release. Instead of learning to follow an ultralight, they’re released among wild cranes and learn the migration route from them. The male of the pair we saw came from this program.

The whooping cranes we saw formed a bond in the summer of 2010 and have been together since. They have nested and produced eggs, but have yet to succeed with a chick. Fortunately, whooping cranes can live into their mid twenties, so there is plenty of room to hope for them as a pair.

There is also room to hope for whooping cranes as a species. Roughly 400 of them currently live in the wild and another 200 are held at research and breeding facilities.

It’s natural to celebrate the recovery of whooping cranes as a conservation success, and certainly many smart, dedicated people deserve boatloads of credit for working to make it happen. But whooping cranes are among the most beautiful creatures that have ever lived. It’s a little more difficult to believe humans can muster the collective will to stop the ongoing destruction of so many other, less charismatic species around the globe.

Thursday, November 20, 2014

U of I Retrocommissioning Group, "Saving the planet two buildings at a time"

U of I Retrocommissioning Group, "Saving the planet two buildings at a time"

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In a recent commentary on the U of I’s progress toward goals from its Climate Action Plan, I noted that much of the credit for that progress goes to a team from Facilities & Services known as the Retrocommissioning Group. Since then, through conversations on campus and elsewhere, I’ve been reminded that few people know much about the group or the work they do. Given our long-term interests in conserving resources and saving money, that’s too bad, because the people who do retrocommissioning are champions of both.

So let me bring you up to speed.

In a nutshell, retrocommissioning refers to a process of analyzing the energy-dependent systems in a building—heating, ventilation and cooling, as well as lighting—and then doing what’s necessary to get those systems operating as efficiently as possible.

Facilities & Services first formed a team dedicated exclusively to retrocommissioning in 2007. It was composed of five people and led by Karl Helmink an engineer with long experience in heating and cooling. Their tongue-in-cheek slogan then was “Saving the planet one building at a time.” Since then, the group has grown to 20 people and it now operates in two teams, so they’ve updated their slogan to “Saving the planet two buildings at a time.” Both teams include engineers, field technicians, tradesmen and student interns.

The teams typically spend about two months on a building, and they employ a highly systematic approach. Their work entails a thorough analysis of available documentation on mechanical systems by engineers, and a comprehensive investigation of operating conditions, equipment, and more by field technicians and tradesmen. 

Members of the team also confer with representatives from the buildings where they work throughout the process to make sure their needs are met. “When our work is finished,” says Helmink, “they’ve got to be happy with the building”.

One straightforward thing the retrocommissioning teams do is identify maintenance issues that tend to multiply in overlooked places as facilities age—things like clogged ducts, stuck dampers, damaged coils and worn out sensors. Beyond attending to such issues, they also focus on ensuring that lights and heating and cooling are on only as they are needed, rather than around the clock. Toward this end they install occupancy sensors wherever they can.

Such tune-ups can have really amazing impacts.

The greatest reduction in energy use from one year to the next? A whopping 56 percent, achieved at the Admissions and Records Building. But even the average reduction in energy use following retrocommissioning is an amazing 28 percent. And because retrocommissioning has now been conducted at more than 50 campus facilities, the cost savings are really adding up, too. Over the past seven years the work of the Retrocommissioning Group has saved the University more than 22 million dollars on energy costs.

Critical listeners might wonder whether the gains achieved by Retrocommissioning are lost over time; I’m happy to report they are not. That’s because the process also involves adding buildings to a centralized computer system monitored by a team member, who can dispatch crews to fix significant problems as they arise. So, for example, if a valve gets stuck open leaving heat on when it’s not supposed to be, it takes little time for the problem to be discovered.

In fact, Helmink pointed out, problems are often corrected before building users are even aware of them. Kind of makes you wish you could have the Retrocommissioning Group work at your home, doesn’t it?

Thursday, November 13, 2014

November brings sandhill crane spectacle to northwest Indiana

November brings sandhill crane spectacle to northwest Indiana

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The calls of sandhill cranes carry on the wind by some magic. Whether they are flying, and your view of them is obscured by a tree line, or they’re feeding in a harvested cornfield, where their rust-stained gray feathers make them difficult to pick out, you typically hear cranes before you see them.

And hearing sandhill cranes is a great pleasure. They talk quietly among themselves in family units, which include mother, father and one or two young of the year, which are called “colts.” (Colts stand as tall as their parents by Fall, but their plain gray “caps” are distinct from the bright red ones on adults.)

What’s more dramatic, though, is the way cranes call to one another as they collect in larger groups, either in flight or on the ground. To me these calls resonate in a mix that brings together something of pigeons cooing, something of geese honking and something less birdy, too—a stick rattled along serrated ridges on a wood block.

You may know by one means or another that sandhill cranes gather by the hundreds of thousands along the Platte River in western Nebraska during their migration north in the Spring. But did you know there’s scaled down version of that spectacle in western Indiana each Fall, one that’s much more accessible to us? It takes place at Jasper-Pulaski Fish and Wildlife Area, which is just 60 miles north of Lafayette.

Sandhill cranes that breed in the upper Midwest and central Canada begin gathering at Jasper-Pulaski near the end of September, and their numbers grow until mid- to late November, when they peak at about 20,000. Imagine that—20,000 of these majestic birds together in the same place less than
half a day’s drive from where you are now.

During their stopover in Indiana, the cranes keep a very regular schedule. At night, they roost in marshes at the reserve, where they’re
safe from predators such as coyotes. In the morning, for about a half hour either side of sunrise, they come together to socialize in Goose Pasture, a vast field that’s overlooked by an observation platform.

The cranes then head out into nearby agricultural fields where they spend the day feeding. There they take advantage of corn that was lost in the harvest, as well as a wide range of other foods—everything from plant materials to worms, insects, mice and snakes.

Your best bet for seeing cranes up close is to cruise the gravel roads south of Jasper-Pulaski (carefully, of course, with respect for the people who live there) and pull over quietly to watch them feed.

The real crane spectacle at Jasper-Pulaski takes place in the hour around sunset, as they congregate again at Goose Pasture before heading back to the marshes for the night. At that time flocks pour in from every direction, and the calls of birds already on the ground blend with the calls of birds in the air to create music like none you’ll hear elsewhere.

This gathering also affords great opportunities to see the cranes “dance”; they bow, they jump into the air, they flap their enormous wings and generally wind each other up, then settle down again, sometimes in a wave of activity that ripples across the field.

If you go to see the sandhill cranes at Jasper-Pulaski you’ll definitely want to have binoculars, and if you have access to a spotting scope bring it along, too. And take extra warm clothes. You wouldn’t to be driven from the observation platform by cold before the twilight show is over.

Thursday, November 06, 2014

Alligator snapping turtles reintroduced in southern Illinois

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If you’ve ever seen a snapping turtle in Illinois, it was almost certainly a “common snapping turtle.” Common snappers can be found throughout the state, and they’re able to adjust to life in nearly any body of water. This commentary is not about common snapping turtles. It’s about alligator snapping turtles, which are bigger, gnarlier southern cousins of common snapping turtles.

Alligator snappers are distinguished by three ridges of spines on their upper shell and a head that looks huge in proportion to their body. They also have a wicked hooked beak. And they get big, too, bigger than any other freshwater turtle in North America, with top weights in the wild reaching 155 pounds.

[Photo by Eva Kwiatek. Ethan Kessler draws blood from an alligator snapping turtle just before releasing it.]

Alligator snappers prefer life in large rivers like the Mississippi, Ohio and Wabash or waters directly connected to them. So they were never widespread in Illinois, which also marks the northern limit of their range. Over the course of the twentieth century, alligator snapping turtle populations in the state were wiped out entirely by habitat alteration and overharvesting. But favorable conditions now exist in enough places to make reintroducing them feasible.

I spoke recently about a project to do just that with two of the people at its forefront, Mike Dreslik, a herpetologist with Illinois Natural History Survey (INHS) in Champaign, and Ethan Kessler, who is working toward a master’s degree in the Department of Natural Resources and Environmental Sciences at the U of I, with Dreslik as his adviser. Here’s what I learned from them.

The current reintroduction, which involves collaboration with multiple other state and federal agencies, as well as the St. Louis and Peoria zoos, involves a long-term effort. That’s because alligator snapping turtles are long-lived creatures, and they don’t reach sexual maturity until they’re 11 or more years old.

This summer Dreslik, Kessler and others released a total of 97 alligator snapping turtles in a creek at the southwestern edge of the state. To say those turtles were released, though, tells only a small piece of the story. On the day they were let go, every one got a health checkup, which included a visual exam and blood work. They were also fitted with tiny data loggers that record water temperature, and 62 them had radio transmitters attached to their shells.

With the help of those transmitters, Kessler and company relocated each turtle three times a week through the rest of the field season. Partly this was to keep tabs on the health of the turtles and to see whether they were competent at life in the wild, since nearly all of them were reared in aquariums at hatcheries or zoos. Happily, they really were and only one of the turtles with a radio transmitter died this year.

Additionally, the information gathered in relocating them will help scientists answer important questions about habitat preferences and movements. The surprise on this front came from the biggest of the released turtles, a 16-pounder. He immediately moved nearly a mile upstream to a big logjam, where he then stayed put for the rest of the season.

The answers to questions about movements and habitat preference will, in turn, help to answer a broader one, which has implications for the prospects of other endangered turtle species as well. As Dreslik summed it up, “How do we reintroduce turtles to the wild with the greatest chance of success?”

For now, though, the more pressing concern about Illinois’ new alligator snappers is how well they cope with winter. We’ll check back next spring to see.

Bonus turtle

Explaining this as part of the radio commentary got too convoluted so I left it out there. But INHS herpetologist Chris Phillips came up with a real surprise as he was groping around in deep, murky water to find one of the turtles with a radio transmitter; he found a wild alligator snapping turtle, the first one in the state since 1984.

[Phillips (left), Kessler and native Illinois alligator snapper. Photo by Mike Dreslik.]

As to what exactly that means, the jury is still out. But given the amount of time and effort that has gone into looking for alligator snapping turtles, no one I spoke with was inclined to take it as evidence of some hidden, viable population.

Thursday, October 30, 2014

Enjoying spiders

[In anticipation of Halloween and the spirit of throwback Thursday, this week's spot comes from 2005, when my kids were still young enough to do just about anything I asked of them.]

Enjoying spiders

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Halloween is upon us, the one time of year people put up spider webs at home instead of taking them down. It’s also a great time to celebrate and explore some of the things that creep us out. Like spiders.

Since children are usually a little more open to these subjects than adults, I’ve enlisted the young naturalists from my house, Jane and Will, to help out with today’s show.

Let’s start with the basics. Kids, are spiders insects?

Both: Nooooo.

How can you tell?

Jane: Spiders have eight legs; insects have six.

Will: Yeah, and spiders have only two body sections; insects have three.

Jane: Besides that, all insects have antennae, and most have wings.

Will: Spiders don’t.

There are more than five hundred species of spiders found in Illinois, more than three thousand in North America. The big ones like tarantulas, orb weavers, and wolf spiders tend to get the most attention, but they represent only a small portion of the spiders all around us.

And spiders are all around us. In an often-repeated bit of wisdom, which I pass along here without scientific confirmation, you’re never more than three feet from a spider.

Spiders thrive in and around buildings, on trees, in grass, under rocks, and in caves. There’s even a spider that lives most of its life under water, using air bubbles trapped in silk to breathe.

Kids, does this mean we’re in constant spider danger?

Both: Noooooo.

Very few spiders are aggressive toward humans. When they bite people it is usually because they have become trapped next to the skin, either in clothing or bedding. This is not to say a bite from a spider can’t be serious. In Illinois, both brown recluse spiders and black widows can deliver a bite requiring medical attention. As a rule, though, people greatly overestimate the likelihood and severity of spider bites. Spider venom is meant for spider prey, which is mainly insects and other spiders.

If it creeps you out to think of how many spiders there are around you, think of how many more mosquitoes, flies, and other pests we’d have without spiders on the scene to eat some of them. Or better still, enjoy some of these cool spider facts.

Jane: Some spiders with fierce names, such as the rabid wolf spider, are really harmless to people. Others, like the black widow, live up to their names.

Will: Trapdoor spiders live in burrows underground. At night they wait by the door and spring out to capture insects passing by.

Jane: Spiders can parachute. As you may remember from Charlotte’s Web, spider young send out a balloon of silk to be carried away in the wind.

Will: A bolas spider swings a strand of webbing like a sticky tetherball to catch moths out of the air.

Is your spider sense tingling yet?

Jane: We sure hope so.

All: This year, think spiders for Halloween.

Thursday, October 23, 2014

Progress on Illinois Climate Action Plan a focus at U of I Institute for Sustainability, Energy, and Environment

Progress on Illinois Climate Action Plan a focus at U of I Institute for Sustainability, Energy, and Environment

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Let’s face it, conservation is rarely sexy. And stories of conservation can be difficult to tell, because they typically lack individual heroes and often turn on doing less of something, not more. To wit. Between fiscal years 2008 and 2014, the University of Illinois at Urbana-Champaign reduced its atmospheric carbon pollution (“emissions,” if you prefer) from 530,000 tons to 450,000 tons. That’s 15 percent.

As an institution we taught, housed and fed no fewer students, did no less research and outreach, and continued our world-class contributions to the arts and culture as before. We even added the significant energy demands of the National Petascale Computing Facility to the mix. And still, we reduced our carbon pollution by 15 percent.

That means we’ve made significant strides toward carbon neutrality by 2050, a commitment we undertook in 2008 by signing the American College & University Presidents’ Climate Commitment.

How did we make such strides? I spoke recently with Ben McCall to find out. McCall is a professor of chemistry at the U of I who also holds an appointment as associate director in the Institute for Sustainability, Energy, and Environment, which was launched in December 2013.

McCall reminded me that roughly 90 percent of campus carbon emissions are attributable to energy. “That’s the big fish,” he said, “so changes we make in energy usage, production and purchasing have the greatest impacts on emissions.”

Conservation—that is, the energy we are not using—is the most important aspect of the energy picture, and “energy use intensity” (defined as energy unit demand per unit of floorplan) is the metric used to gauge that. Between 2008 and 2014 energy use intensity on campus was reduced by 20 percent.

McCall was quick to point out that the lion’s share of credit for this reduction goes to the work of Retrocommissioning teams from U of I Facilities & Services. “They’re the ones who do the unglamorous work of going from building to building to tune up the mechanical systems, and that’s where the biggest savings come from.” (Those in charge of Retrocommissioning at F & S calculate the cost avoidance made possible by their work to be near $22 million.)

The context for McCall’s remarks about energy on campus was a broader conversation about the Illinois Climate Action Plan (iCAP), which was developed in 2010 and includes other targets relating to sustainability. One of the important targets for 2015 that we’ve already reached is a 20 percent reduction in the use of potable water. Another we’re nearing is the purchase of 30 percent of the food used by U of I Dining Services from local sources.

In his role at the Institute for Sustainability, Energy, and Environment, McCall is coordinating the work of six recently established Working Advisory Teams, which bring together students, faculty and staff who have interests and expertise in various aspects of sustainability. Just this week these teams finalized assessments of progress the U of I has made on its current climate action targets, and released suggestions for revising the plan.

If you’re interested to see what the teams came up with, or even explore the possibility of joining one yourself, keep an eye on the Institute’s website, It’s a work in progress, but materials related to progress on the climate action plan should be available within the next week or so.

Thursday, October 16, 2014

Ancient oaks link us to the Big Grove

Ancient oaks link us to the Big Grove

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When people think about the landscape of central Illinois prior to European settlement they tend to think “prairie,” vast expanses of flat land covered in tall grass and tall flowers. And for the most part, that image is pretty accurate.

But groves of trees intruded on the grasslands here and there, especially on the eastern edges of rivers and streams, which created natural breaks to prairie fires driven by winds from the west.

Such groves were dominated by fire-resistant species of oak, and interspersed with hickory, ash, walnut, sugar maple and linden trees as well. 

[Photo by L. Brody Dunn. The bicentennial oak on the lot of the Quaker Meetinghouse in Urbana, IL.]

Prairie groves were quite hospitable to humans compared to the prairie itself, offering game and shelter, as well as respite from some of the discomforts of life in the open. They were preferred sites for American Indian villages, and the first places to be settled by Americans of European descent coming from the east.

One of the largest of these timbered areas in our region was named by settlers of the early nineteenth century the Big Grove.

As it was mapped in the original survey of the area in 1821, the Big Grove covered about 10 square miles. Its western edge roughly paralleled the Saline Branch, the stream that drops into Urbana from the north and runs through Busey Woods and Crystal Lake Park before turning east toward St. Joseph. Along its southern edge the Big Grove extended to about where Urbana’s Main Street runs today.

If you’re familiar with Urbana and the locales just north and east of the City, you know there’s no forest left that would merit the name, “Big Grove,” most of the wood from those trees having gone into houses, fences, farm implements and fires long ago.

But here’s something really cool. Some trees that began life in the Big Grove still stand today. You can touch them. Heck, you can hug them. They’re the kind of trees that elicit that response from people.

Near the corner of East Main and Maple Streets, a bur oak that predates the Declaration of Independence rises to a height of more than 80 feet from the yard outside Long’s Garage.

Farther from the center of town on East Main, a still larger bur oak can be seen on the eastern edge of the site of the Friends Meetinghouse. We can take this tree to be roughly 240 years old now, based on calculations made in 1976, when the International Society of Arboriculture recognized it as a “bicentennial tree.” 

At Leal Park, which is on University Avenue near the Carle complex, there’s yet another bicentennial oak marked with a plaque.

Greater numbers of oaks that predate European settlement can be seen—and hugged—at some other Urbana Park District sites. Some of the largest trees in Crystal Lake Park and Busey Woods are relics of the Big Grove, as are 10 or so of the trees at Weaver Park on East Main Street.

If you’re interested to do a little more reading before you head out on your treehugging adventure, check out the Website “Children of Giants” recently established by UI professor of entomology Stewart Berlocher at

Thursday, October 09, 2014

Local action on global warming

Local action on global warming

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This summer, the Champaign-Urbana Mass Transit District maintenance facility got something really cool to go on top of its roof—a big photovoltaic system, more than 1200 panels.

According to Jane Sullivan, whose title at MTD is Grant Manager and Sustainability Planner (and who is a 2012 graduate of the UI School of Earth, Society, and Environment, where I teach), it’s the biggest solar array currently operating in central Illinois.

It will generate 350,000-kilowatt hours of electricity over the course of a year, which translates to about one quarter of the electricity used there. (The maintenance facility is a busy place, operating 24/7 when the U of I is in session and providing full service maintenance for the District’s fleet of 102 buses.) Sullivan said the investment in solar is in keeping with the broader environmental mission of the District. “We’re interested in finding as many ways as we can to reduce our environmental impact, and reducing greenhouse gas emissions is an important part of that.”

The motivation for a solar array that went online at the First Mennonite Church of Champaign-Urbana this summer was similar.

Holly Nelson, a member of the congregation’s “Green Team” who helped to instigate the project and see it through, characterized it this way: “We had taken smaller steps toward being more sustainable and caring for creation, including reusable dishes and a community garden. This was something bigger for us.”

The 32-panel array at the church is of a different scale than the one at MTD, but so is the need it serves. It generates the equivalent of roughly two-thirds of the electricity used to run the facility over the course of a year.

[Photo by Jason Hawksworth. Holly Nelson on the roof with solar panels at First Mennonite Church of Champaign-Urbana.]

About forty percent of the money invested in the First Mennonite project was covered by a rebate from the Illinois Department of Commerce and Economic Opportunity. (If you’re wondering about solar for yourself, your business, or a nonprofit, you can look into this incentive here.) But the majority of the funding came from donations by the congregation dedicated specifically to the project. To Nelson, the congregation’s enthusiasm for the project was evident in how quickly that money came in. “It’s the biggest investment our church has ever made,” she said, “and we raised all of it in a month.”

You may remember from a commentary last year that Champaign resident and U of I physics professor Scott Willenbrock had installed solar panels on his family’s home in a quest to achieve “net-zero” energy use; that is, to generate as much electricity as the family used at home.

That’s an ambitious goal for a house built in 1929. But when we spoke recently, Willenbrock reported that in the first six-month period for which he had data (January 1 to July 1 of this year) they had achieved it. On top of that, they did so even with the demand for electricity added by an all-electric car they bought in April.

You can learn more about Willenbrock’s project, which has applications for anyone interested in conserving or generating energy at home at

In terms of conserving and generating energy, no building in town—or in all of the U. S. for that matter—is more ambitious than the new home of Electrical and Computer Engineering at the U of I. You can visit there and learn more about it at a public dedication ceremony tomorrow afternoon. The building is located at 306 North Wright St. and the ceremony begins at 1:00 p.m.

Thursday, September 25, 2014

An ecological look at acorns

An ecological look at acorns

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Last week I found a walnut on my windowsill, a big fat one with an unblemished bright green husk. Soon after, another appeared stuck in the wheel of my car. Now they’re cached everywhere around the outside of our house, from the shelf on the grill to the flowerpots on the deck.

Acorns are everywhere now, too, as anyone who bicycles where there are oaks can attest. A person’s got to keep both hands on the handlebars to avoid having them wrenched sideways.   

While these seeds may be present me with minor annoyances, they’re much more interesting and important from an ecological perspective.

Scientists group walnuts and acorns together with hickory nuts and beechnuts in the category of hard mast. This they distinguish from soft mast, which generally refers to fruits like crabapples and blueberries but can also apply to other parts of plants that serve as food for wildlife.

[Photo by author. Gray squirrel eating an acorn in a Chinkapin oak.]

According to Ed Heske, a mammal ecologist with the Illinois Natural History Survey at the U of I Prairie Research Institute, “The most important thing about hard mast from the perspective of wild animals is that it’s storable. Without hard mast many mammals that don’t hibernate in winter would have little to eat.”

Of course, while it’s a good thing for squirrels that acorns can be stored for eating over the winter, it is not in the interest of oak trees to expend all of the resources needed to produce such wonderful seeds if all of them wind up as squirrel food.

Evolution has provided oaks with a clever reproductive strategy to avert that outcome, referred to as masting cycles.

 In most years, oaks produce a sort of baseline quantity of acorns, and populations of animals that depend on them become calibrated to that. But every few years or so, depending on weather and other factors, the oaks of a local area synchronize their energy and produce a bumper crop—up to a hundred times the baseline quantity of seeds in some species. With populations of acorn eaters limited by the leaner years, chances are that some portion of acorns from the bumper crop will go uneaten and grow into the next generation of oaks.

There is another wrinkle to this story, though. Some years back Heske and a colleague conducted a study that found acorns would result in new oak seedlings only if some of them were buried by squirrels and then never recovered, a situation expected primarily when acorns are superabundant in mast years. Otherwise something—whether it was a deer, turkey, mouse or weevil—always ate them up from the soil surface before they had a chance to germinate.

In addition to promoting new generations of oaks, Heske explained to me, bumper crops of acorns initiate a cascade of other ecosystem effects. Extra acorns, for example, enable forest-dwelling mice to reproduce especially well; during mast years they can add an extra litter or two, and add to the size of their litters as well.

Good for the mice, right?

But what’s good for mice is, in turn, good for great horned owls and the other predators that eat mice. They generally experience a bump in reproductive success in the year following a mast year.