A Closer Look at Cones: Norway Spruce

by Doug Morin

 

Thwack……thwack……

What was that, I wonder?  Never mind, I have to focus.

thwackclunkbang………

Bang? Was that a bang?

thwackbang……thwackthwack

I couldn’t help myself.  I opened the window and look down to the garage and driveway.  Nothing moved.  The neighbors weren’t even home.  Back to work.

thwackthwackthwack

I raced over to the window, catching a flash of rust-colored fur bolting along a spruce branch to the inner tree.  I looked down; the driveway was covered with spruce cones.  I stayed put, waiting to catch the culprit red-handed.  A minute later, the squirrel ran boldly out one of the long spruce limbs, 40 feet above the ground.  It ran to the end of the branch, hung down off it’s back feet, grabbed a cone with its front feet, chewed the cone’s base for a few second, then let it fall.  thwackclunkbang……… The cone tumbled to the ground, hitting the neighbor’s roof, the side of our house, then my housemate’s car.

Norway spruce. Note the swooping branches and drooping branchlets. Source: http://bioweb.uwlax.edu/bio203/s2009/madisen_neil/

Over the course of the last week, the squirrel dropped about 200 cones into our yard and driveway, by my estimate.  The cones were coming off a Norway spruce (Picea abies) tree in our backyard.

Native to Europe, Norway spruce is one of the main trees in the forests of Germany, Switzerland, Austria, and Russia.  In the U.S., it is commonly grown as an ornamental and in plantations, but rarely establishes on its own.   It is widespread throughout the cities and suburbs of the Northeast, so keep an eye out and you will start seeing it everywhere.

Norway spruce may be the tree most easily identified from a distance.  Once you get the search-image, you will be able to recognize it while driving 60 miles an hour on the highway.  An evergreen, Norway spruce has short, dark needles.   The trees usually grow 50-80 feet tall and two feet in diameter, and often have branches almost all the way to the ground.  And, most importantly –here’s your 60mph field mark— branches off the main stem arc upward (“swooping”) while branchlets growing from the main branches are long and hang down (“drooping”).  Swoop and droop – it’s that easy.

Now, back to the cones.  When you imagine a cone, I bet you think of a dry, brown one, light as a feather.  But, cones are not always so. The dry brown ones most of us imagine have passed maturity and already released their seeds.  In contrast, the cones pelting our house were still developing – leathery, green (or pink early in the season!), and dense.  Plenty dense to dent a car, as we discovered.

But these cones are only one of the two kinds of cones conifers produce.  The big cones we tend to think of (and the kind now all over my driveway) are female cones.  They are usually between 1 inch and 6 inches long depending on the species and produce seeds under their scales.  Squirrels eat the seeds, explaining why our squirrel was amassing a collection of female cones.  Lesser known are male cones.

Separate structures from female cones, male cones tend to be small (1/2 inch or less in length) and not as long lasting (they often disappear in days or weeks).  They produce pollen for a short time in the spring then, having fertilized female seeds, their job is done, and

they die back.  Interestingly, the difference between male and female cones explains why the squirrel was dropping cones from high enough to bombard our roof.

Male cones on left, Female cones on right. Sources: http://projectbudburst.blogspot.com/2010/05/look-at-conifer-phenology.html, Wikimedia Commons

Most trees concentrate male cones on their lower branches and female cones on their higher branches.  This serves an evolutionary role: it prevents self-fertilization. With male cones down low and female cones up high, pollen from male cones must get blown by the wind to get high enough to reach a female cone. This wind will usually carry the pollen to another tree.  If, however, the cones were intermixed or the males were on top, the pollen would fall directly into its own female cones.

So, if the tree wants to mate with another tree, rather than itself, it puts its female cones up high… giving them plenty of time to accelerate as they fall before pelting roofs, cars, and the occasional unsuspecting bystander.

 

 

 

 

The Sensual Slug

by Danielle Owczarski

During the first cold days of fall in Burlington, I had a chance encounter with a handsome slug on my way to catch the bus. As I hurried past, it glided effortlessly across the moistened slate walkway, its black leopard-print pattern catching my eye. The image of the mysterious figure drifted through my thoughts during the short bus ride to campus.

Limax maximus, also known as the great gray slug and leopard slug. (Photo:© R.J. McDonnell, University of California, Riverside)

Originally, when I thought about writing a blog on the natural history of the great gray slug (Limax maximus), I imagined the story to be a simple, thoughtful, interesting piece; little I knew of the great gray’s sensual secrets. Those of you with weak stomachs or other sensitivities related to natural reproduction may want to surf your way to a blog about cooking or kittens. This story is for those with unquenchable curiosity and a sensible grasp on nature’s sexual exploits.

The great gray is a hermaphrodite. Within its slimy skin layer are organs that support both female and male reproduction. Lucky for the great gray, it is not a simultaneous hermaphrodite like the banana slug, who can self-fertilize. No, the great gray must entice a partner to share in the event of reproductive triumph.

L. maximus, native to Europe, and naturalized in the United States and Australia by way of food transport, leaves a thick string of mucus on the ground in early summer to attract its mate. This activity happens mainly during the night hours for this nocturnal species, who feeds on mushrooms and withered plants.

When its partner detects the secretions, it will follow closely, taking a soft nibble on the tempter’s behind. In a grand chase (at a slug’s speed), the two head for an overhanging feature (a brick wall, tree, or mossy rock). They begin to writhe in what seems a blissful engagement, rubbing and twisting around each other’s lubricated bodies.

As the foreplay advances, they begin to fall gently from their perch, attached only by a dense strand of slime, their pendulous bodies entwined in mid-air. Next, in unison, from an opening (gonopore) on the side of each slug’s head, the penises emerge and begin to entangle. The elaborate spiraling of the white translucent penes forms the shape of a flower similar to that of a blossoming morning glory. The unified form then takes on an azure glow and fertilization ensues. The sperm travels up through the twisted organs, through the gonopores, and inside the slug’s body finally reaching the eggs. The act is complete, both fulfilling their reproductive desires.

It would be biased to leave you with an unspoiled depiction of the great gray’s reproductive story. On some occasions when the entanglement becomes too complex and the slugs are unable to pull apart, apophallation must occur. They chew off one or both penises to relieve the imbroglio and the great gray is left with one working organ to continue its life’s work.

For those of you who can’t get enough, check out David Attenborough’s video clip of the great grays in the act: Limax maximus Reproduction Video.

Blue jays and bird colors

by Nancy Olmstead

The woman who lives downstairs from me feeds the pigeons almost every morning.  I know she’s out there when I hear a great swooshing of wings: dozens of pigeons flutter down to our driveway to greet her.  She’ll also put out peanuts for the squirrels.  Sometimes a crafty blue jay slips in there and grabs a peanut.

One of those wily blue jays flew up to the fire escape outside my kitchen window, and as it was adjusting its peanut, I got a good look at it.  Blue jays are such a bright blue color; it’s shocking in our Burlington landscape of brown and gray city birds.

Birds come by their colors in different ways.  The blue of a blue jay is not a pigment; it’s created by the physical structure of the feather.  The color is all in the way the molecules are arrayed.  If you ground up a blue feather, thus breaking apart the structure, there wouldn’t be any color anymore.  If you backlight a blue jay feather, you won’t see the blue anymore.  Next time you find one, place it between your eye and a flashlight beam, or hold it up to the strong sun – no blue.

In contrast, northern cardinals borrow their bright red color from plants.  The carotenoid pigments that make a cardinal red can’t be synthesized by animals; they have to be ingested from plants in a bird’s diet.

What are all those feather colors for, anyway?  Scientists know that birds have good color vision.  In species where the male and female are colored differently, color is usually important in mate choice.  A female American goldfinch is picky about which male she partners up with – a male with lovely, bright yellow color is preferred, while a male with drab plumage could find his partner straying.

Colors can also be structurally important.  The most abundant feather pigment is melanin, which gives strength to areas of the feathers that need to be particularly resistant to wear, like wing tips.  Herring gulls are a good example of a bird with these melanin-rich wing tips – they show up as an almost-black color.  Many terns also have this pattern of dense melanin pigmentation at the wing tips.

I’m not sure what role color plays in the life of a blue jay, but I’d like to find out.  Male and female blue jays look pretty similar to me, so perhaps color isn’t a big deal in mate choice.  Or maybe there are small, subtle color variations that I haven’t picked up on yet.

I should team up with the lady downstairs.  I could bring the blue color chart and maybe she could bring the bag of peanuts.

Fern Surgery

by Carly Brown

The hand saw sits on the disinfected countertop. Fresh fern-appropriate soil waits in a bucket next to my workstation.  I wheel the ferns in on their ‘gurney’, a garden cart that I pull through the greenhouse to the office. I pass by the succulents, the lipstick tree, and finally the cacti. I am wheeling the ferns in for surgery.

As a greenhouse student employee I work in House 2 amongst the pitcher plants, orchids, and ferns. Once a week I scout the area for greenhouse pests. My hand lens is more or less permanently pressed to my right eye as I search for spider mites, thrips, and aphids (more on that in another post).  Today, however, is fern bisection and transplant day. I have transplanted before, but I have never cut plant clusters into pieces to put a smaller individual back into the original pot. The ferns have not only outgrown their pots, but will soon outgrow their area in the greenhouse if they are not cut back.

Removing the large leather fern from its pot is not a task for the weak. Its deep green, shiny, waxy-looking fronds rise up above my head as it sits on the counter. The pot is dense with secret underground growth. Using all of my strength, I flip the pot upside down and rap it against the edge of the counter until the fern slides out of the pot. Catching it in my hands, I flip the fern right side up. Intricate roots and underground rhizomes support its structure enough that it retains the pot shape. The rhizome on a fern is comparable to the stem on a flowering plant. Though it is below the soil it gives the plant a sturdy structure, much like our legs.

I grab my surgical tool: the saw. The goal is to divide this fern into four equal sections. I start the cut, putting all of my muscle into it, but the saw does not make progress. I move the saw back and fourth, but it does not go deeper into the soil. Is this possible? Am I trying to saw through a piece of metal that I did not see? My muscles strain as I push and pull – back, forth, down – until I finally feel the saw going deeper into the soil. After the saw makes it halfway, something gives. I have made it through the hard, almost woody, rhizomes of the fern, and can now detangle the more delicate roots.

Pulling apart the fern base, I am mesmerized by the beauty in the mess of rhizome structures weaving in and out of each other. I have admired ferns in the forests and fields, and have recently tried delicious fiddleheads smothered in butter.  Despite my above-ground admiration, I have never known what goes on in the life of a fern below the cover of soil.  After making a second bisection I place one section of the fern in its old pot and fill it with new soil. This new soil hides the fern’s secret – its solid, intricate, rhizomatous base. After returning the leather fern to House 2, I drench the dry soil with water to jumpstart the growth that will eventually reveal the secret to another naïve student employee on transplant day.

 

 

 

Witch-Hazel: The Honeybee’s Last Forage

by Leah Mital-Skiff

We extracted honey this weekend from our backyard hive.  The late date of this final extraction is evident in the density of the deep-amber goldenrod-dominant honey.  Its slow movement through the series of filters on a cold day reminds our family that we should be out apple picking rather than forcing our bees to further stock up for winter on chilly days. I worry every year that we have taken too much too late from the bees as I watch the late-blooming asters begin to wilt at the beginning of fall.  The forage for our honeybee colony is reduced this time of year as they work harder to fill and cap their final honey chambers for winter.

The dynamics of supply and demand have reversed.  Where flowering plants have competed for pollinators throughout the spring, summer and early fall, the pollinating insects now face a shortage of pollens and nectar as most flowers and deciduous plants have senesced for the year. However, one plant, witch-hazel, has evolved to capitalize on this shift.  On the cold days of fall when other plants have lost their color, witch-hazel bursts into a show of yellow flowers beckoning our bees from the warmth of the hive to forage just a bit further into the fall.

Witch hazel flower photo taken by Neahga Leonard through a hand lens for magnification.

Witch-hazel, Hamamelis virginiana, is a shrub native to Vermont and a common understory tree with a high shade tolerance.  Its anti-competition-late-season-pollination strategy comes with additional adaptations to produce a viable seed crop and environment for germination.  Like our honeybees, which remain in the hive on colder days to protect the queen, few other pollinators remain flying this late in the season.  While witch-hazel does not compete with other flowering plants for pollinators, it does contend with temperatures and reduced daily sunlight that signal pollinators to reduce their flight.  For this reason, most of the witch-hazel flowers go without pollination and the plant produces few fruits.

Flowers and last year’s orange-brown fruits co-occur in the fall. Photo: Neahga Leonard

With its leaves dropped, witch-hazel’s other unique adaptation becomes evident against the backdrop of the bare northern hardwood forest in the fall.  Unlike other plants, witch-hazel flowers and fruits simultaneously.  The fruits, however, are a full year behind the flowers, having finally matured from last year’s mid-fall pollination. They have persisted on the shrub all winter to mature in the fall along with the new flowers.  Two shiny black seeds are ejected explosively (a distance up to 3 meters) from the woody capsules.  One theory of the name witch-hazel is attributed to the sound of the expelled seeds hitting the dry leaves of the forest floor.  People associated this eerie phenomenon with witchcraft practiced deep in the woods on still autumn days.  This theory competes with the more popular reason behind the name.  The bendable, forked branches were used by witches as dowsing rods, wishbone-shaped twigs, to find groundwater sources, valuable metals, or even missing children.

Enjoy this last show in the woods once the blaze of foliage has come to an end and even the goldenrods have given up for the year.  If you are lucky enough to witness the explosive seed dispersal and find the seeds among fallen leaves, the rich, white oily interior is edible, collected and prized in the past by Native Americans. Perhaps, it will be warm enough for our honeybees to make their final foraging flights to meet you there; their focus will be the flowers.

New Life Storms into the Forest

by Liz Brownlee

The roots stretch high into the sky – ten feet, maybe fifteen.  Soil hangs midair, clinging to the roots. A tiny white pine sits in the depression, reaches for the warm, gaping hole in the forest canopy.

The red maple once towered ninety feet tall, spreading its arms wide into the canopy.  Screech owls made their home in the tree.  Woodpeckers searched for dinner.  Black Rat Snakes lounged in its branches.

Its leaves were the first to turn each Fall, and their brilliant red told of cool nights to come. Its seeds – little helicopters – spun down on the Spring breeze.

Now that giant lies on the ground, another victim of Hurricane Irene’s powerful winds. This forest, at Mud Pond Conservation Area in Williston, is littered with downed trees, thrown on top of each other like so many pick-up sticks.

Downed trees could seem like a tragedy to a passerby.  But the white pine seedling, small as it may be, knows a more complete story:  falling trees create new life in Vermont’s mature forests.

Forests of tall, old trees are cool, dark, moist places.  The leaves from full-grown trees absorb almost every bit of sunlight before it can reach the ground.  Seedlings starve for warmth and light.  They cannot grow, and they can wait years – even decades – for a tree to fall.

A storm, then, allows new life.  Wind is the most common way Vermont trees come toppling to the forest floor. The downed red maple is a “wind-throw,” because it fell in a powerful storm.

The suddenly sunny forest floor is a very happening place.  White pine and birch seedlings shoot up practically overnight.  Deer munch on young plants. Fungi break down the tree’s trunk, and worms, beetles, and salamanders move in.

The forest could not grow anew without downed trees.  Just ask the white pine seedling.

 

For hiking in Mud Pond, and other locations in the Town of Williston:  http://town.williston.vt.us/index.asp?Type=B_BASIC&SEC=%7BE8A7EC77-4332-4BA8-BBEF-6B1AB2B4F06C%7D&DE=%7BCF447A7E-7514-4078-9910-933255CB6967%7D

 

Natural Destinations: Silvio O. Conte National Fish and Wildlife Refuge

By Danielle Owczarski

A view of Lewis Pond and the Nulhegan River Basin during October foliage.

Far from Burlington, hidden in the low basin of the Nulhegan River in the Northeast Kingdom, awaits a little known National Fish and Wildlife Refuge. The 26,000 acres of refugium established in 1999 encompasses three headwater tributaries to the Nulhegan River, itself a tributary to the 7.2 million acre Connecticut River watershed. Protection of this basin is critical to the health of many species of plants and wildlife and to the water quality of the Connecticut River. The Silvio O. Conte National Fish and Wildlife Refuge was created to protect these valued natural resources.

The North Branch of the Nulhegan River.

Now is the best time to visit the quiet boreal and northern hardwood landscape. Red and sugar maple, balsam fir, tamarack, yellow birch, and beech color the landscape in the fall months, nourishing the soul’s need for creative inspiration. Lewis Pond, the Nulhegan River trail, and Mollie Beattie Bog (named after UVM Alumni and first women director of U.S. Fish and Wildlife), are a few of the Tolkienesque attractions within the refuge. Start your tour at the exemplary Visitor’s Center in Brunswick, VT, to collect trail maps and wildlife viewing guides and explore the interactive interpretive exhibits.

Mollie Beattie Bog, a black spruce woodland bog, is a significant natural community in Vermont. The interpretive trail includes a handicap accessible boardwalk.

The headwaters of the Nulhegan offer a tranquil and wild setting for fly fishermen and women. The Black Branch and North Branch, along with Lewis Pond, comprise healthy brook trout populations, which are periodically stocked by the Vermont Department of Fish and Wildlife. The most recent stocking in the Black Branch on June 20, 2011, included 100 eight-inch yearling brook trout. Studies conducted in 2000 indicate that self-sustaining wild brook trout populations exist within the cool clear tannic waters of the refuge streams. The ideal habitat supports healthy macroinvertebrate populations that provide nourishment for the trout throughout the year.

A wild brook trout caught in the Nulhegan River.

The refuge also supports scientific research studies. While driving or hiking along the refuge roads, lined and filled with gravel and dirt, you’ll come across plots of young low grasses and shrubs, managed to encourage breeding and nesting of the American Woodcock (Scolopax minor). The area is also home to such projects as the Migratory Bird Stopover Habitat Study, the Canada Warbler Study at the Nulhegan Basin Division, Effects of Habitat Fragmentation on Carnivore Distribution and Fitness Indicators in Vermont Forests, and the Study of Public Use on the Nulhegan Basin Division.

Be sure to enjoy the ride.

This land is truly a place for anyone with a passion for the outdoors whether hiking, bird watching, hunting, fishing, observing, or renewing. So turn off the computer, grab a friend, and immerse yourself in Nature.

For directions to and in-depth information about the Silvio O. Conte NFWR:

http://www.fws.gov/r5soc/come_visit/nulhegan_basin_division.html

A Conversation with Norman Myers

by Liz Brownlee

UVM Field Naturalist and Ecological Planning (FNEP) students sat down with Dr. Norman Myers this week for a casual conversation.  He is on campus this week for multiple talks, including a “Gund Institute Tea” this Friday. 

 We bantered back and forth about biodiversity, social engagement, and the future of the planet.  Dr. Myers is quite the personality – his answers are full of stories and anecdotes, and he loves challenging the audience with some questions of his own.  Below are some of the questions from our conversation.

 Dr. Myers revolutionized conservation some thirty years ago when he introduced the idea of “biological hotspots,” which concentrates efforts on small areas of the planet that host a huge array of native species. Dr. Myers is also a UVM Marsh Professor-at-large.  Meet this environmental mover and shaker this Friday and ask questions of your own this Friday, Oct. 7, at the Gund Institute’s weekly “Gund Tea” in Room 133 of the GreenHouse Residential Learning Community.

 

FNEP: Why do we care about the diversity of life on earth (biodiversity)?

Myers: The one most important thing in the world is biodiversity and mass extinction.  How do I demonstrate that?  In 1958 I went to Kenya (as a photographer).  Within minutes of stepping off the plane I was in a preserve, staring at a lion’s tonsils, looking a giraffe in the eye.  There was the giraffe, doing its own thing in its own world.  I say to hell with everything else.  There was a rightness about it.  I’m shocked and appalled that we’re still letting these species disappear.

In the 1980’s science thought we were losing one species per year.  I found that we’re actually losing one species per day. The worse news is that the rate of extinction is to increase soon. It’s because we are not only destroying species’ habitats, but also evolution’s ability to create and adapt.

If I had a million dollars to devote to research, I wouldn’t put it to counting daisies. I’d put it to figuring out why we’re letting this holocaust continue.

 

FNEP: Where are the leverage points?  Where are the places we can put a concentrated effort and make large amounts of progress?

Myers: It’s biodiversity hot spots.  These are the best places for our funds. Some conservationists say it’s performing triage, but the reality is we’ve been performing triage for fifty years.  In the 1980’s we spent $17 million to save the California condor – it’s great that we saved the bird – but at that same time we could have addressed mollusks in the Mississippi River and saved 200 species.  Investing funds in one species automatically keeps money from other ecosystems and species [in other places].  So we need to address priorities for ecosystems and for evolution.

 

FNEP: What gets you out of bed in the morning?

Myers: Your question is, “Why do I stick with this game?” I could have made more money selling used cars. But isn’t it exciting to be the generation that faces this thing and wins? It’s exciting to be alive for such a cataclysmic problem, and know that I’m trying to stop it. It’s empowering to know I can [help stop it].

Listen, I have an advantage over you lot.  When I was a little boy and the War was on, I used to listen to Churchill every night. The US and England were hiding, and Hitler was winning at every turn.  Churchill came on the air and said, “No! We can do it.  We can change this. We can win.” And he knew he was speaking rubbish.  But he kept talking and we did win.

 

FNEP: The difference between the War and mass extinction is that we had a common evil to oppose.  Today, not everyone agrees it’s a priority: we want to save a bird but we also don’t want to see kids starve.

Myers: But sometimes one problem’s solution can solve others, too.

And who would have thought that in 1950 that Americans would stop smoking, that the Berlin Wall would fall, that Apartheid would end?

 

FNEP: Those efforts are characterized by social pressure, good leadership, and subsets of people who cared deeply.  They knew what the world looked like without their problem, they could aim towards it. How do we do that with biodiversity and conservation?

Myers: Do you know the story of Henry V from Shakespeare?  The English are backed into a corner by the French, they are outnumbered ten to one.  Henry spoke to the troops: “If you don’t want to stand together, shoulder to shoulder and fight them, here’s money – leave.”  By the next morning, there were twice as many fighters.

 

FNEP: One major issue with saving biodiversity is the shear number of people on the planet.  But how do you begin a conversation about fewer people and less consumption when it’s every species’ imperative to reproduce and prosper?

Myers: I’m encouraged by a conversation I heard about (because it means the conversation is happening). It happed at the Vatican.  Someone pointed out that the edict of “Go forth and multiply” was issued when the Earth’s population was two.  He pointed out that the smallest families on Earth are in Italy.  And the smallest family size in Italy occurs in Rome.  And the smallest family size in Rome is…well, you get the idea.

Canada mayflower – more than meets the eye

By Nancy Olmstead

What is an individual plant?  It’s pretty clear when you are looking at an individual squirrel, or an individual blue jay: it starts at the tail and ends at the head.  The question gets harder to answer when you look at some kinds of plants, including many of our New England forest wildflowers.  Scientists who study forest plants need to be able to tell one individual from another.  If they can’t, their studies might accidentally be made up of many samples of the same few organisms, which would bias the results toward organisms that were sampled multiple times.  One example of an understory plant that presents this challenge is Canada mayflower (Maianthemum canadense).

This cute little plant can be found from the arctic to the Atlantic in a broad swath across northern North America, through the upper midwest and the iron belt states, and down the Appalachian mountains to northern Georgia.  When you’re walking in an upland New England forest during the late spring, summer, or early fall, keep an eye turned toward the understory.  You are likely to see a Canada mayflower plant.  You might see areas where many Canada mayflower plants grow in a loose patch close to the ground.  Some of the plants are just a single, teardrop-shaped leaf growing about four inches above the ground, while other plants have two or three leaves.  From late May to late June, you’ll see a crown of 10-30 tiny, white flowers on the plants with multiple leaves.  Some of the flowers will turn into reddish, round fruits by summer’s end.

If you gently dig up the base of one of these plants, you’ll find a slender root (or two) that runs horizontally into the soil.  If you keep digging carefully, you may be able to follow that slender root right over to a neighboring “plant.”  And you could go on to the next “plant,” and maybe to the next, and so on.  Eventually, some root connections break down, but they are all the same plant.  Canada mayflower has a clonal growth habit – it uses roots like other plants use twigs, to spread out leaves and capture more light.  Some clones cover more than 20 square feet; old ones can reach 30-60 years of age.

So what is an individual, and does it matter?  Maybe it doesn’t matter to a hiker just admiring the flowers.  But for a scientist trying to study plant responses to the environment, it matters a great deal.  If we want to understand how plants are reacting to acid rain, or dealing with a changing climate, we have to know where a plant begins and ends.  Our questions require us to take independent samples.  With molecular techniques, researchers can test individual stems to determine genetic identity.  But it’s expensive and time-consuming.  Our understanding of these beautiful wildflowers will therefore be limited until we discover an easy way to tell who’s who.

The Fall Migration of Raptors

By Emily Brodsky

Just about when the leaf peepers begin flocking to the roadways to observe Vermont’s spectacular autumn foliage, an equally-enthusiastic set of nature lovers is trekking up the peaks to watch a different seasonal event: the fall migration of raptors.  Also known as “birds of prey,” this majestic group includes the eagles, falcons, hawks, vultures, ospreys, and the less-familiar but no-less-impressive group called the harriers, of which North America has only one (the beautiful Northern Harrier).   Perched on a mountain outcropping, one can predictably see large numbers of these birds as they make their way to southern climes.

Whether you’re a veteran bird-watcher or a novice, raptor-watching (usually referred to as “hawk-watching,” even though other types of raptors are included) is a great way to spend an autumn afternoon.  One of its draws is that the birds are highly visible.  Unlike the diminutive songbirds, which hop around incessantly and hide in dense shrubs, raptors are large, steady, and during migration, exposed.  Also, because each group of raptors flies differently and has a distinctive shape, these birds are easy to tell apart.  The peregrine falcon, for example, has long, pointed wings, which it flaps continuously for its fast, powered flight.  In contrast, the bald eagle rarely flaps and its broad, sturdy wings make it look like a flying plank.  At the popular hawk-watching sites, you’re likely to find fellow observers on the summit to help you with identification; learn the shapes and flight patterns of the major groups and you’ll be a hawk-watching maven in no time.

 

So when and where is a Vermonter to begin?  The peak of fall raptor migration is from mid-September to early November; try going at different times of the season to see different species.   The most popular hawk-watching sites in Vermont are Mount Philo, 15 miles south of Burlington, and Putney Mountain in the southeast corner of the state.  Snake Mountain in Addison and Mount Ascutney in Windsor are also decent spots, as are Coon Mountain, just beyond the ferry terminal in Essex, New York, and Mount Tom in Massachusetts, straight down the Connecticut River from Brattleboro.

In addition to being a popular place for recreational hawk-watching, Putney Mountain is also an official migration monitoring site.  Because raptor migration is predictable and easy to watch, people have been counting migrating raptors and recording their numbers since 1934, when the first official count site was established at Hawk Mountain Sanctuary in Pennsylvania.  Since then, numerous similar counts have been established all over the globe, from the Panama Canal to the Strait of Gibraltar.  The long-term migration data collected at these sites allow scientists to monitor raptor populations; numbers vary greatly from year to year, but over long periods of time, scientists can identify trends.  The decline in juvenile Bald Eagles migrating past Hawk Mountain Sanctuary in the 1970s alerted Rachel Carson to the threat of DDT to these important predators, and she wrote about this trend in Silent Spring, the influential book which led to the ban of that harmful pesticide.  Visit the Putney Mountain Hawk Watch just for fun, or participate in the count to play a role in history.

You may be wondering why people hike up mountains to watch raptors migrate, instead of just observing from their driveways.  Do mountains simply afford better views of the sky?  The answer is that raptors concentrate along specific routes during the fall migration, and just as you’re more likely to find lots of cars on I-89 than on a dirt road in the sticks, you’re much more likely to see large numbers of raptors along these migration flyways.  Flyways tend to stick to mountain chains, because these topographic features allow for easy flight.

Source: http://donsnotes.com/nyc-nj/hawk-watch.html

As you can probably imagine, migration is exhausting.  When we humans are exhausted, we can take a nap and recharge; to a raptor, exhaustion usually means death.  Some raptors, such as Broad-winged Hawks, fly as many as 4,500 miles in about nine weeks to reach their wintering grounds.  To make it that far, they must do whatever they can to save energy along the way.  Lucky for raptors, there are some great energy-saving tricks.

When winds blow against a barrier such as a mountain, they’re forced upwards.  During migration, raptors fly along the sides of mountain ridges to take advantage of this upward push of air, called an updraft.  Instead of flapping their wings to generate lift, raptors can simply spread their wings wide and ride the updrafts like a surfer rides a wave.  Updrafts can carry raptors hundreds of miles along a continuous mountain chain like the Appalachians, which conveniently runs from north to south.  Not only does this strategy save migrating raptors an enormous amount of energy; it also makes for a great show, since updrafts carry the birds right past the slopes.

Source: http://www.loudounwildlife.org/HHHawksInAir.htm

Updrafts are helpful when the wind blows.  Early in the fall, however, when the sun is still high and the air is calm, raptors rely more heavily on another phenomenon of physics. You’ve probably seen hawks or vultures flying in circles, high in the sky with their wings outstretched.  These birds are using a trick called soaring flight.  As you know, the surface of the Earth is quite variable; some spots are covered with rocks, some with woodlands, and some with houses and streets.  When solar radiation hits these surfaces, they each heat up at a different rate, and thus, the air just above the ground heats up unevenly.  In spots where the ground is warm, the air rises, forming columns called thermal air currents (or thermals, for short).  Raptors find these thermals, and spiral upward without having to flap their wings.  When they get nice and high in one thermal, they exit and glide toward another (losing altitude but gaining distance), and they rise up again.  In this way, they can travel long distances without expending much energy.  Mountain slopes heat up faster than the valleys below them, which means they’re good places for thermals; thus, raptors stick to the mountains even on calm days.

Mountains aren’t the only places in which to spot large numbers of migrating raptors; these birds tend to follow shorelines as well.  Thermals don’t form above water bodies like they do over land, because water releases heat slowly and evenly.  Without thermals or updrafts, raptors must use flapping flight – the most costly kind of flight.  For migrating raptors, flapping across a large expanse of water is risky business: if they run out of energy, they drown.  Consequently, most raptors avoid flying over large water bodies, and when they reach one along a flyway, they hug the coast – or, if they must cross, they find the shortest crossing.  Short crossings and narrow strips of land between water bodies act as concentration points, or bottlenecks, funneling thousands of raptors over the land as they avoid the surrounding water.  Examples are the south-facing peninsula of Cape May, New Jersey, the narrow crossing from Europe to Africa across the Strait of Gibraltar, and the thin strip of coastal plain at Veracruz, Mexico.

Migration behavior varies among species.  Broad-winged hawks, for example, depart for their approximately 4,500 mile trek to northern South America in early September when the thermals are strong.  Aptly named, Broad-winged Hawks are built for soaring flight.  Although Broad-winged Hawks are solitary for most of the year, they flock during migration.  Scientists believe flocking helps the birds to find the best thermals, although it could serve other purposes as well, such as protection; even most raptors have to worry about predators.  Broad-winged Hawks are one of the main attractions at raptor watch sites, since it’s possible to see hundreds or even thousands of them soaring together.

Unlike Broad-winged Hawks, Cooper’s Hawks are mediocre long-distance flyers.  These birds have stubby wings and long, rudder-like tails; they’re built for maneuvering among the branches in their forested habitats.  Cooper’s Hawks don’t generally migrate very far, and some don’t migrate at all.  Those individuals that do migrate tend to do so later in the season than Broad-winged Hawks, departing in October and November, and dropping off along the way as they find suitable wintering grounds.  They rely heavily on updrafts to save energy during the trip, and are easy to spot on north-facing ridges.

You may ask: why do the birds go to all this trouble, anyway?  Or, better yet: if they don’t like the cold, why don’t they just stay in the south, where the weather is toasty-warm year-round?  A common misconception about migration is that it’s prompted by temperature change.  Since we like to follow the warmth of the sun in the wintertime and many of us head south to Florida beaches, we assume birds and other migratory animals share our preferences.  In most cases, however, migration relates to temperature only indirectly.  In actuality, migration is mostly about food.

As the northern days grow shorter and the temperatures drop, plants cease to produce fruits.  Annual plants reach the ends of their lives, while perennials drop their leaves and transfer their sugars into stems and roots for winter storage.  Many of the insects and mammals that feed upon these plants turn in for a months-long slumber, or stock their larders with seeds, nuts, and other high-energy morsels and settle into their winter dwellings.  Ice creeps over the surfaces of lakes and ponds, sealing in their inhabitants until the spring thaw.  Carnivorous birds suddenly find themselves with little to eat.  So, they follow the food.  And, because it coincides with warmer weather, the food just so happens to be in the south.

When migratory raptors reach their wintering grounds, they must compete with resident birds for food and roosting sites.  This works out okay in the winter, when the birds need only worry about themselves; once spring comes along, however, the birds must compete for nest sites, and food for their offspring as well as for themselves.  Making the grueling return journey is worthwhile, since the raptors will have their choice of nesting spots when they reach their mostly vacant northern homes.  They’ll also get there just in time for dinner; after the snow and ice melt, there will be fish, rodents, songbirds, and juicy insects around just about every corner.