Zero for Two

By Bob Engel
Marlboro College Professor Emeritus of Biology and Environmental Science

I was trying to decide whether to feed the birds today.  If I could see some insects, so could my feathered buddies.  Who would want to beat on a black-oil sunflower achene to get the seed inside when insects were buzzing around?

But because I’m a softy, I had put out the feeder and was sitting on the porch watching a lot of nothing.  Maybe six or seven juncos were hunting on the ground nearby.  No chicks, titmice, or nuthatches, and no thieving red squirrels.  I started out into the yard to bring in the feeder.  And WHOOSH — for the second time in two days, the noise of wing and tail feathers controlling very sharp turns stopped me.  It was a male Sharp-shinned Hawk in full attack.  The juncos panicked and scattered.  They all made it to cover in the privet hedge.

Sharp-shinned Hawks are the smallest and most common species of the three species of so-called Accipiters — specialized, bird-eating hawks — that breed here.  All three species are built to chase birds, and all have relatively short, round wings and long tails.  Between the constantly beating wings and the long tail, they can turn on a dime and rigidly steer through those turns.  

The Sharp-shinned Hawk, Cooper’s Hawk, and Northern Goshawk all look pretty much alike, but they increase in size from about 11 inches, to 16 inches, and then to 21 inches.  The Goshawk, the largest is also a bit stockier.  The size of these bird eaters also determines what they attack.  

“Sharpies” are after typical little brown birds: chickadees, juncos, sparrows, maybe a nuthatch. Cooper’s Hawks take jays, woodpeckers, and maybe robins.  I saw one in Arizona that had eaten so much of its unlucky prey that the hawk’s crop stuck out as it a balloon had been inflated in the hawk’s crop.  A Goshawk hunts a little differently and takes some mammals in addition to larger birds.  A couple of years ago, I saw one perch in a big pine tree in front of our house.  It was a very pale gray bird, and, therefore a male.  He sat quietly.  Five minutes later, a Mourning Dove flew into the field and the sit-and-wait Goshawk leapt into pursuit.  He was immediately outflown by the dove.  The lesson?  If you’re a larger hawk that waits to surprise a bird, the prey has to be pretty slow, clueless, or maybe a grouse paying too much attention to berries.  

So back to my bird.  It was also a male (substantially smaller and with a brighter breast than a female), and because of its intense, focused attack, it had not seen me.  I froze and the hawk landed on a small branch maybe eight feet away.  He seemed to be composing himself…a bit of preening of some primary wing feathers, a little fussing with the scapularies (feathers at the shoulder) and some bill wiping.  Bill wiping shows up after all sorts of behavior, some of it aggressive, and seems to “redirect the mind.”  Off he went, and finally saw me at about three feet.  He had failed here and was going to try somewhere else (no sightings since).  At this point, I am not certain whether he was the same bird that our feeder birds, mostly chickadees, escaped yesterday.  Today, three chickadees perched near the hawk in the still naked tree and scolded him vigorously.  He looked up at them, and I was tempted to imagine that he considered the whole event degrading.  I would have.

Quite a few years ago, a couple of ornithologists published an interesting paper in the evolutionary and ecological journal American Naturalist.  Am. Nat., as it’s called by the cognoscenti, prints papers that include both some new data and a resulting, novel idea.  The authors looked at a variety of mammal-eating hawks like Red-tailed Hawks (they eat a few snakes, too) and the three bird-eaters we’ve talked about here.  The data they found (mostly in a variety of papers) showed that bird-eating hawks are much less successful per prey strike than are mostly mammal eaters or fish eaters.  

They mused that if food is hard to get, evolution might generate substantial size dimorphism amount the sexes of all three of the bird eaters.  Why?  Because they would hunt differently sized birds, thereby reducing competition within each accipiter species.  Among hawks and eagles, the Accipiter males are significantly smaller than the females. This is all interesting, but pretty theoretical.

What I had seen were two failed attacks by male “sharpies.”  How do you note a successful attack?  When you find a pile of feathers.  I have seen lots of feather piles, and I have seen lots of chases, but I have never seen an Accipiter actually catch its meal.

The Bird Diva, Bridget Butler on VPR...and soon to be in Chester

Did you happen to catch The Bird Diva Bridget Butler on Vermont Public Radio's annual spring migration show? It aired today at noon, and it is now available for streaming on VPR's website.

We loved listening to Bridget and Jane dish on birds; it really jumpstarted our enthusiasm for getting back into the swing of things with our birding lives.

LISTEN: "In for a Landing: The Spring Bird Show, Vermont Public Radio, 5.24.17"

We have a great diversity of birds here in Vermont. I encourage folks to get out; even if it’s just during your morning cup of coffee. Step outside in your backyard. It’s really amazing this time of year what’s moving through.
— Bridget Butler, speaking on VPR

Want to improve your birding skills so that you can identify what exactly is moving through? This Thursday you'll have your chance in Chester! 

We are beyond excited to welcome Butler this Thursday night at 7pm at Chester's NewsBank Conference center for "Bird is a Verb". She'll answer your questions and share her insights on the birds we'll likely to see in our backyards and nearby woods. Save $2 a ticket by purchasing your tickets online before Wednesday; tickets will also be available at the door. 

A Thought-Provoking Night With Dr. Alan K. Betts

Dr. Alan K. Betts was on hand at Chester's NewsBank Conference Center on Wednesday night as part of our adult speaker series. A well-known atmospheric scientist, Betts explained how global climate change is ushering in more extreme weather and shorter winters to New England. Scientists have predicted that by the end of this century the weather in Vermont will resemble the climate that is now in northern Georgia.

He stressed that there are actions we can take now to make a difference, including conserving the natural resources we have. He emphasized that significant strides have been made over the last 10 years to increase the energy efficiency of appliances, cars, heating systems, and lighting for our homes. Earth’s dwindling supply of non-renewable resources—along with the harmful gases they produce—makes conservation so important.

Betts went on to describe how the consumption of fossil fuels has steadily increased since last century and has contributed much to the degradation of our environment. Climate change, global warming, extinction of several endangered species, depletion of the ozone layer, increase in air pollution are just a few of the effects from which our environment is suffering. Many European countries have taken steps to move toward clean and green energy sources like solar energy, wind energy and geothermal energy to save energy and leave fossil fuels behind.

Canada's government site includes a useful checklist that outlines ten things you can do now to help mitigate climate change. How many items have you tried? >

We want to send a big thank you to Alan for sharing his passion for the environment and science; and we are grateful of course to the community of folks who came out to learn from him! 

We welcome The Bird Diva, Bridget Butler on Thursday, April 27th. Tickets are available now!

Calling All Spring Breakers: Programs for Kids, April 18-21

Join our Environmental Educator daily this week from Tuesday-Friday, April 18-21, for hands-on, pro-planet activities, nature games and creative eco-art for families. We will offer a special program each day and our museum will have extended hours for you to explore. We are open from 10am-4pm from Tuesday-Friday this week. 

Come see us; pack a picnic and take a walk in our woods!

Program Line-up

And don't forget! We are open Saturday as well!

Twigs & Stems // April 2017

Here are a few links from around the web that caught our attention in recent weeks. Have you seen something that stuck with you that you'd like to share? Post it in the comments! Love what you see here? Follow us on Facebook, as we often post these goodies as we find them. 

On Our Radar: Into the Woods With Our Children Presentation, April 7th

We recently received word about an interesting talk aimed towards parents and caregivers that will be co-sponsored by Windham Regional Woodlands Association, along with other local organizations. We think it might interest many in our community!

Read on to learn more about this free event!

In her talk, “Into the Woods with Our Children”, forester Lynn Levine of Dummerston will outline a hands-on approach to awakening in youngsters an enduring love of the natural world. A focus of this talk will be how to break down the barriers so that children will want to go into the woods (rather than playing with their electronic devices) and how we can help them “need” to return to the woods, again and again. This event promises to be particularly valuable for our region’s environmental and science teachers. 

The event will take place on Friday, April 7th at 7pm at the Vermont Learning Collaborative, 471 US Route 5, Dummerston. For more information, see the Windham Regional Woodland Association's website or email Lynn directly at

Hello Spring: April Events at The Nature Museum


Fall in step with the unhurried pace of nature with The Nature Museum!

Find simple ways to relax and recharge with nature's help at these upcoming events!

Engage with fantastic speakers and other like-minded kindred spirits who share your love for the natural world. The Nature Museum is dedicated to providing programs for everyone, from preschoolers to adults, related to biology, earth science and natural history. Most importantly, we offer discovery-learning programs to engage people in the wonders of nature and develop more earth stewards.


The museum is delighted to offer multiple programs in April, including special expanded hours during the week of spring break for area schools. The Museum will be open from Tuesday, April 18 through Friday, April 21 from 10 a.m. – 4 p.m.

Please stop by and see us!


Wednesday, April 12th

Dr. Alan Betts presents “The Impacts of Climate Change on Vermont” at the Newsbank Conference Center in Chester.

Award-winning atmospheric scientist, author and commentator will help Vermonters learn more about the ramifications of climate change and discover how we can move toward a more adaptable and resilient future.

Saturday, April 15th

Earth Day is every day! Mike Clough from The Southern Vermont Natural History Museum presents “VT Wildlife & Working Landscape” at the Grafton Inn's Phelps Barn.

Enjoy a multi-media program complete with live music and live wild animals! 


Earth Day is Every Day:
Spring Break Fun

Join our Environmental Educator daily Tuesday-Friday, April 18-21,  for hands-on, pro-planet activities, nature games and creative eco-art for families.

Tues. 4.18:  “Fur, Feather & Bones” at 11am. For families, by donation.

Wed. 4.19: “Blabbing About Birds and Talking About Turkeys” at 11am. For families. By donation.

Thur. 4.20:  “Now You See Me, Now You Don’t” at 10am. For preschoolers and families. $5.

Fri. 4.21: Museum open from 10 am – 4 pm.

Thursday, April 27th

Get a spring tune-up just in time for bird migration season with The Bird Diva, Bridget Butler. Learn tips and tricks for bird identification, find equipment and resources, discover birding by ear and ways to find different birds.

Winter: Relentless

By Bob Engel
Marlboro College Professor Emeritus of Biology and Environmental Science

The average high temperature in Albany, New York has risen from 31°F in January to 46°F on March 20th. Average lows are in the mid-twenties.

Here in Marlboro, a place of never-ending winter, we’ve had almost a week of scattered lows that were at or just below zero. Some of our recent highs were below Albany’s normal lows. On March 14 we were buffeted by a nor’easter with high winds and maybe 18 inches of snow. 

March is a tough time for animals. The easy food is long gone and almost nobody is carrying much body fat. Some are actually digesting their muscle tissue; the quest for energy becomes unrelenting. But what if you’re inactive or hibernating? How do you deal with temperatures at or well below freezing? How do you prevent the rupture of cell membranes in tissues that get below zero? It’s just like a beer bottle left outside. When water freezes it occupies 10% more volume than it did as a liquid. Pop goes the bottle cap and out comes a plug of beer. Cell membranes could also rupture.  Bummer.

So that’s our question for today. How much freezing, if any, can a dormant or hibernating animal tolerate? And how do these critters prevent becoming partly or mostly frozen?

Let’s look at the obvious, first. All resident birds keep their body temperatures well above freezing, usually just a bit above 100°F. A few, like the Black-capped Chickadee, drop their temps at night to conserve energy (like we do with our thermostats). But then they go right back up to “hot” for the next harried day of foraging.  

Just a few of our mammals are true hibernators (e.g., a few bats, woodchucks, and a few obscure rodents like jumping mice), meaning that they drop their body temperatures to 34°F up to 40°F, and are virtually inert. A pile of sawdust placed on a woodchuck stays right there until mid-spring. But hibernators do not freeze and they will elevate their body temps a bit if they happened to have not chosen a good spot to spend winter. Intermittently active types like chipmunks do not hibernate in this sense. Bears stay inactive but hardly drop their body temperatures. This is not an option for small hibernators—they’d run out of stored energy. To be sure bears are ready for anything even vaguely digestible when they emerge.

That leaves the “cold-blooded” types like herptiles and arthropods, and this is where is gets interesting. Their body temperatures drop to whatever their ambient temperature is.  But freezing may not occur even if the ambient temperature is well below freezing.

I used to worry about some frogs like spring peepers and wood frogs. The story was that they snuggled down into the leaf litter (thereby getting some insulation) and then “hoped” for snow that provided more and prevented freezing. But what about cold periods without snow?  Should we assume that some freezing will cause tissue damage and elevated winter mortality rates for these creatures? Well, no. 

Several lab studies have shown that a variety of frogs can tolerate total freezing in a few larger biological compartments, but not all. In some species, the duration of the freeze is important; a close relative of the peeper, for example, can tolerate freezing for about a week. But what about a longer period? Then the trick moves to preventing freezing in more critical body compartments like those that contain important organs.

Almost all of the “cold blooded” critters produce some kind of antifreeze. It’s just like what’s in your car’s radiator; freezing is precluded by preventing ice formation or ice crystal growth. The first antifreeze identified was glycerol, a pretty simple three-carbon molecule that prevents ice formation by bonding to water molecules. It’s common in polar fish and a lot of other things. We have since identified sugars like glucose (in the wood frog) and a variety of proteins that bond to several sites of ice crystals, preventing further ice growth. These proteins are found in everything from insects to reptiles. Proteins are expensive to make (glucose is robbed from the liver), but they prevent even more expensive outcomes like death.

There is one more biochemical trick: the antifreeze proteins and sugars also exert an osmotic pull on water surrounding organs like the heart and digestive glands. The resulting “dried” organs are much less likely to freeze.

Even with these molecular solutions, reptiles and amphibians start to peel away as it gets colder with latitude. Southern Canada is about the best they can do (woods frogs and a few other “true” frogs, and the common garter snake are exceptions). But insects go much further north. The champion is a gall producer in Arctic willows (appropriately called the willow gall fly). As a larva, it can survive minus 60 °C (-76°F)!  It’s body fluids are half water and half glycerol!  It stole all that carbon from the willows, who took it from the air. It’s range includes Alaska; I don’t know if it goes all the way to the end of land in Greenland.  The Arctic willow does that, which is as far north as any woody plant goes.  Tough bugs; tough plants.