Loons – the clumsy birds

If you’ve spent time on an undeveloped lake in northern North America or Europe you’ve probably seen or heard loons.  Their calls are loud and eerie, ringing out over still water and carrying far before fading amongst the trees.

Here in Vermont the Common Loons (Gavia immer) have finished nesting, the young have hatched, and the adults are teaching their young how to survive.  Over the past few months they’ve flown in from their winter grounds, found nesting spots, defended them, reproduced, and will stay until the first ice begins to cover the lakes.  The adults carry immature young on their backs.

Kevin T. Karlson photography – common loon with chicks

When the time comes for over-wintering loons fly to the oceans.  In the US there is an excellent loon tracking program that allows you to watch the movements of individual loons over the seasons.

Loons are large waterfowl with a distinct black and white pattern, reminiscent of Penguins, Auks, Razorbills, Puffins, Terns, the questionably named Imperial Shag, and a host of others.  These birds are patterned white on the belly and black on the back for the same reason that Orca and other aquatic predators are; from below the white blends into the sky, and from the above the black blends into the water (or ground), providing camouflage from both prey and predators.

Loons are excellent fliers with long, surprisingly narrow wings

Loons are excellent flyer and fantastic swimmers, but have difficulty on the ground.  Their large bodies are front heavy and they cannot stand upright, as a result they push themselves along the ground, sliding on their bellies. The name Loon derives from Scandinavian names for lame or clumsy, “lúinn” in Icelandic and “lam” in Swedish.

Their inability to walk means that their nests must be close to the water and that the nests must be in well protected places, usually islands or extremely wet peninsulas.  As more and more lake sides are developed there is less and less nesting habitat for loons.  In addition a pair of loons needs 5-20 hectares (12-50 acres) of clear undisturbed water on a lake with many small bays and nooks and a healthy fish population.  Boats and swimmers can easily disturb nesting loons and studies indicate large reductions in nesting success in areas where people come into close contact with nesting loons.

There are few places that meet the nesting requirements and loons are highly territorial during nesting season.

Most of the time loons are heard, not seen, and when seen it is usually from at least a mild distance.  Several weeks ago I came across a freshly dead loon on the shore of a small pond.  Finding dead animals is always interesting as you have an opportunity to look at them up close and discover things you wouldn’t otherwise know.

The background of this particular loon is that it was an undersized male, blind in one eye, that (according to the banding codes) was new to the area.  It fought with the male of an established nesting pair and lost the fight.  A fellow from the Vermont Center for Ecosystem Studies moved the loon to a nearby lake where it stayed for several days, seemingly falling into poorer and poorer health until I found it on the beach.  Upon request I collected the loon so that it could be sent to one of the research labs and an autopsy done on it.

Small male loon found dead

Small male loon found dead

The first thing that caught my eye was the sleek iridescence of the feathers, tending towards a blue-purple on the neck and with an oily sheen on the black back feathers, but it was the legs that fascinated me.  Chicken, duck, and most other familiar birds have round legs.  This makes sense, these birds must support their weight while walking, or waddling in some cases.  Loons don’t walk so their legs don’t need to be especially strong side-to side.  They do need to cut smoothly through the water however, and as such they are blade-like in shape presenting a narrow front to reduce drag.

The white neck feathers stand proud from the black feathers

The white feathers that ring the neck stand proud, rising 2-3mm above a background of short, fine, dense black feathers.  Loons are cold weather birds and, like all water birds, they have dense feathers.  I did not realize just how dense those feathers are though.  Loon feathers feel like rich fur, not feathers, almost felt-like in texture and density.

White speckled back feathers

The white speckles on the loon’s back remind me of an Escher print.

Here in Vermont loons are popular animals and there has been some good work done to protect loon habitat.  As a result, loon breeding success is higher in this state than the national average.  Bans on lead sinkers for fishing have helped the loon population as well as fewer individuals are swallowing the lead and getting poisoned from the metal.

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Birds, but especially Warblers

Birds occupy a place in our imagination like few other animals.  They are colorful, have beautiful songs, and they can fly!  Who doesn’t wish they could fly?

Young Red-tailed Hawk (Buteo jamaicensis) before the tail turns red

We eat them, decorate our bodies with their feathers, listen to their songs, and keep them as pets.  In westerns the high-pitched keening cry of the Red-tailed Hawk symbolizes the openness and loneliness of the range, setting the mood and implying that the rugged, lone gunman is as comfortable on the dusty range as the hawk is in the air.

Traditional societies have based dances on the mating dances of birds, clothing has been influenced by the color and patterns of birds, and we assign symbolism to specific birds; doves for peace, hawks for aggression, eagles for freedom, the unfortunate dodo as a dead-end in stupidity, and many more.

Here in the US the we chose the Bald Eagle to symbolize our nation, choosing a bird that is at least as much of a scavenger as it is a hunter, over the objections of Benjamin Franklin.  Make of that what you will.

Some birds live only a few years, others like parrots and albatrosses live as long as a healthy human.  Many birds can “fly” under water as well as in the air, the Water Ouzel of the American West, Loons, Cormorants, and Gannets that plunge into the water like falling rockets, diving many meters down to chase fish.  Some birds have given up the air entirely, Penguins retain their flight in the water, but the Ratities, an ancient lineage including Rheas in South America, Ostriches in Africa, Emus in Australia, and the extinct new Zealand Moa returned to their dinosaur origins, running at high speed on the ground, forgoing the air forever.

Corvids, crows and jays, Parrots, and Cockatoos are renowned for their intelligence, problem solving, and in the case of Corvids, tool use.  These birds rival small children and chimpanzees in their mental abilities.

Birds also can tell us about changes in climate and the environment.  Banding them allows for long-term identification of individuals.  Feathers can be analyzed for isotope ratios, telling what the birds have eaten and where.  Populations can be tracked to see how they respond to changes in environmental conditions.

Vermont Center for Ecosystem Studies employee banding a bird on Mt. Mansfield

I am not an ornithologist, I find birds to be largely mystifying.  I don’t seem to have the ear necessary to distinguish species based on their calls, a vital component of birding.  Despite this, I do greatly appreciate birds and try to photograph them when I can, in part to help me learn, in part because they are pretty, and in part because birds are often easier to see and are more prolific than many other animals.

Birding is a popular activity.  Of all groups involved in conservation and outdoor activities, birders have the highest average income, and companies that make the high quality spotting scopes and binoculars necessary for this activity adjust their prices accordingly.  Many of the most interesting and colorful birds are tiny and fast, necessitating patience and luck, or good equipment, or, most often, a combination of the two.

Warblers are popular birds to watch in New England.  New World Warblers are an often colorful group of small passerines, commonly called “perching birds”.  The name derives from their sparrow-like appearance.  Many of the New World Warblers over-winter in the neo-tropics, flying up to New England as the weather warms and food becomes available here.  Most of the ones I see are in the Septophaga genus, meaning “moth-eating”, though this is sometimes misreported as meaning “fly-eating”.  Others fall into the Cardellina and Geothlypis genera.  I am not sure what the origin of Cardellina is.  Several of the birds in this genus are reddish or pink, and others have a lovely song, it may be a comment on a loose similarity to Cardinals.  Geothlypis roughly means “earth warbler”, perhaps reflecting the essential silliness of many scientific names.

Over the last few years I have managed to take photos of a small number of them:

Canada Warbler (Cardellina canadensis)

This lovely little Canada Warbler was on the ridge-line of Shenandoah National Park and didn’t care that I was nearby.  I heard the song and had to hunt a little bit to find him.

Common Yellow Throat (Geothlypis trichas)

This Common Yellow Throat followed me through the woods as I waded through ferns and sedges in a wet wooded meadow near my house.  It didn’t seem afraid of me at all, more curious than anything.  It kept the caterpillars in its beak, suggesting that there was a nest with young close by.

Black-throated Green Warbler (Setophaga virens)

A few months back I heard a soft but rapid twittering in the woods on my morning walk.  Over my head a flock of 5 or so little birds flitted back and forth faster than I could follow.  One of them briefly touched down and held still for just long enough to snap this photo.  From there I was able to figure out that they were Black-throated Green Warblers.

Black-throated Blue Warbler (Setophaga caerulescens)

On our bird-banding day on Mt. Mansfield this little Black-throated Blue Warbler was found in the mist net.

Yellow-rumped Warbler (Setophaga coronata) western subspecies on the sunflower stalk, eastern subspecies held in hands

The Yellow-rumped Warblers may be the easiest of the warblers to see.  They range from California to New England and have been divided into several sub-species that are nearly indistinguishable to my eye.  The eastern variant is known as the Myrtle Warbler (Setophaga coronata coronata) and the western variant as Audubon’s Warbler (Setophaga coronata auduboni), but they are both Yellow-rumped Warblers to me.

Yellow Warbler (Setophaga petechia)

Finally this small Yellow Warbler was in an apple tree in deep shade.  It sat and watched me for several minutes, then flitted away.

Learning these birds has given me a greater appreciation for them, although I must admit that the task of learning these little guys would have been much more difficult if I couldn’t take photos of them and take the time to look closely at their details.

Away Dog! Apocynaceae, the Dogbane family

Near my house, next to the road the ground is sandy with a scattering of pebbles in the mix.  Like much of Vermont what is not bedrock is ground up glacial debris deposited when the vast continental glaciers melted away.  The ground is sandier than most places at my house because I am perched on the southern slope of a small rock outcrop, a place where the downward pressure of the glacier was lighter, water flowed under the ice, and fine sediment was deposited.

In that sandy ground there are wild strawberries, mosses, dandelions, fleabane, hay scented ferns, a few coneflowers, some potentillas, Allegheny blackberry, a little bracken fern, and a small stand of dogbane (Apocynum cannabinum) with delicate pink flowers.

Hemp Dogbane (Apocynum cannabinum)

Before moving to Vermont my only experience with this plant was via books.  I always wondered why it was called Dogbane.  Was it like negative catnip for dogs?  Or was it simply toxic to dogs?  Apparently it is a toxin, and not just to dogs.  Ingestion of any portion can induce cardiac arrest and both the family and genus name literally translate to, “Away Dog!”  Apocynum cannabinum has, thick, milky sap, much like a milkweed, indeed Milkweeds (Asclepiadoideae) are now considered to be a subfamily of the Dogbanes (Apocynaceae).  Other members of the Dogbane family include two of my least favorite plants, Oleander and Vinca, both from the Mediterranean and common in California where they were introduced as ornamentals.  Oleander can be seen in any urban environment in Southern California, most often as a highway divider plant.  The sap is extremely toxic, raising painful rashes, and the smoke can be lethal if inhaled.  Vinca, more commonly known as periwinkle, is  common in Northern California where it invades riparian areas, covering both ground and small trees in a dense, vining mat of glossy green leaves studded with pretty blue flowers.  It is nearly impossibly to eradicate once in place.

In the past some Apocynaceae species were used to make a poor quality rubber, others for toxin to apply to arrows.  Some species produce edible fruit and others edible flowers.  We extract heart drugs from a few of them as well.

The dogbane in my yard, Apocynum cannabinum, is a traditional North American source for extremely strong fiber, hence the “cannabinum ” species name, referring to the hemp-like characteristic of the plant.  Common names run from simply Dogbane, to Indian Hemp, Wild Cotton, and Hemp Dogbane.  The fibers are stripped from the stalk in late fall and can be twisted into a fine, strong cord.  Cords made from dogbane were prized for their great strength and used for sewing, fishing lines, and other work requiring fine cordage.

The Hemp Dogbane ranges from calf high to chest high.  The ones in my yard top out at waist high.  The have an odd branching structure, perhaps best described as irregular opposite.  The main stalk continually divides in a binary fashion, with one side acting as a dominate leader, this pattern is often repeated on the side branches, but in some cases buds on both side of the stem will form side branches instead.  The result is a roughly Y shaped plant that rapidly spreads as it grows.

Apocynum cannabinum whole plant.

The leaves are opposite and the undersides are covered with a fine pubescence.  I expect that the hairy leaves are an adaptation to help cope with moisture stress.  Plants often evolve this trait to create a boundary layer of trapped, still air that aids in preventing moisture from being blown away.  The upper leaf surfaces have a matte waxy texture, a little like nasturtium leaves.  Water beads and runs off of them rapidly.

Apocynum cannabinum leaf hairs

The seeds are held in long, horn-like pods.  This time of year few of the seed pods have developed, but a couple of plants are a little further along in the cycle than others.

Apocynum cannabinum seed pods, not fully developed

Few of the leaves have any insect damage, but the flowers are popular with a number of insect species.  I’ve seen ants, flies, bees, and moths going to them.  Hidden amongst the flowers are predators as well.  The Goldenrod Crab Spider (Misumena vatia) seems fond of my dogbane.

Goldenrod Crab Spider (Misumena vatia) playing parlor games with a fly

Goldenrod Crab Spiders are so called because they often hide amongst the bright yellow flowers of goldenrod, a common meadow plant in New England.  The spiders change color from white to yellow and back again based on input from their eyes.  The yellow color seeps up to stain their carapace, providing camouflage.  When they move to a pale flower the production of this pigment stops and the spiders slowly turn white once more.  Experiments show that the spider will not change color if it cannot see what color plant it is on.

These are not web building spiders, they are ambush hunters, grabbing unsuspecting prey in their wide arms.

The smell of the flowers is odd and difficult to describe, incorporating many scents including a dusty sweetness and a faint rankness like dried meat on the edge of going bad, but they are pretty.

Happy Aphelion! Wait, what’s that and how does it relate to the climate?

Well, today is one of the most interesting days of the year for me.  This year, 2012, July 5th is aphelion, the day that Earth is furthest from the sun in its orbit.

It is rare (in the tens of thousands of years scale) that the northern hemisphere summer solstice are so close to aphelion.

The time during the year that aphelion and perihelion (when we are closet to the sun) changes over a roughly 100,000 year cycle, known as the Milankovitch Cycle.  Our orbit around the sun is not a circle, it is an ellipse with an eccentricity of about 0.0167.  This orbit both changes shape and rotates around the sun much like a spirogram tracing out a flower-like shape.

Ellipse with 0.5 eccentricity. Earth has a much smaller eccentricity, making the orbit more nearly, but not exactly a circle. Aphelion and perihelion are the two ends of the egg shape.

Perihelion precession

 

It is summer in the northern hemisphere, a time when people often say things like, “We are closer to the sun than we are in winter.”  This is not really true.  Summer is a product of the angle at which Earth is tilted, right now Earth is tilted so that the northern regions lean toward the sun.  In terms of orbit we are actually at the furthest point Earth gets from the sun.

This has interesting implications in terms of the global climate.  This means that right now winters tend to be warm (the planet is closer to the sun) and summers cool (the planet further from the sun).  In the big picture this places us in the midst of a global cool cycle, the type of situation that tends to lead to ice ages, like the one we are emerging from.

The climate picture is not so simple, though.  Even in terms of celestial mechanics there are other factors that play into the climate picture.  Two large, cyclical factors are the precession and wobble of the Earth. One of these is the obliquity, or the angle at which Earth is tilted.  This is our Axial Tilt, and it is currently 23.4º, but the Axial Tilt changes between approximately 22º and 24º, over a 41,000 year cycle.  This affects where the tropics lie and how much solar energy different regions of Earth receive.

Range of Axial tilt – Wikipedia indicates 22.1º to 24.5º , other sources vary on the exact outer limits of the range, but they are all near 22º and 24º of tilt.

The final large scale cycle that comes into play is Axial Precession.  Spin a top, or a gyroscope; the handle by which it was spun precesses, or rotates around the axis of spin at a fixed angle.  In the case of Earth this cycle varies between 19,000 and 23,000 years.

Precession – just like a top or gyroscope, Earth’s axis of spin makes a slow circle

No single one of these factors leads to an ice age or global tropical forests, they must combine in just the right way to set the conditions.  These cycles are like waves in water, sometimes they cancel each other out, other times they reinforce each other.  Past climate records show clear evidence of the effects of these cycles.

NASA – Orbital Time Series showing the cyclic nature of the three major orbital cycles

NASA – Solar Insolation (energy received from the sun) and O18 (an heavy isotope of oxygen) records in sediment indicating temperatures at the time the O18 precipitated.  O18 is heavier, so it takes more energy to keep it aloft, and water made from this isotope tends to precipitate first when the temperature drops.

Once the orbital conditions are right then, other Earth surface factors come into play.  Where mountain ranges are, whether oceans are polar or tropical, how saline the oceans are, the arrangement and distribution of the continents , and volcanic activity, such as the Deccan and Siberian Trap.  These are immense lave flows in India and Siberia that pumped immense amount of greenhouse gasses into the atmosphere and seem to have strongly affected the climate.  Even short duration, one-off events such as the 1815 eruption of Tambora in the Dutch East Indies (now Indonesia), can have global climate effects.  Tambora is implicated in what is commonly known as The Year Without Summer when the global temperatures dropped by 0.4–0.7 °C , leading to massive famines across the northern hemisphere as  result of immense crop shortages.  This may have been a period of low solar activity as well, adding to the poor growing conditions.

Impacting bodies also can play a major role in the global climate.

The upshot of this is that we really should be paying close attention to the current rapid warming trend as it is happening at a time when it appears, from the large scale cycles, that conditions are not right for a warming trend of the magnitude we are experiencing.  This is a warning sign, one that we need to pay attention to.

The climate always changes, and that is as it should be.  The problem we now face is that our physical and social infrastructure has been built around the idea that the changes are small and seasonal rather than global and systemic.  Our cities, roads, fields, power generating systems, and economies are based on things pretty much staying as they are, which will not happen.  Even without us tipping the scale the climate would not stay the same.  We need to be aware of this and act accordingly, looking at the much larger picture.

If we don’t, well, life on Earth will be just fine in a few tens of millions of years, but we may not be around to see it.  If we continue on the path we are now taking, we many not even be around to see the northern summer occur at perihelion.

This is our planet.  Right now it is the only one we have.  Understand it, enjoy it, and please don’t break it.

The good folks at NASA have put together a great, short paleoclimate primer at the link below, which is where the last two charts come from.

http://earthobservatory.nasa.gov/Features/Paleoclimatology_Evidence/

The first three images from from the Wikipedia article on Milankovitch Cycles – they had the best diagrams.

I will return to the usual, smaller scale aspects of nature in the next post, which will be about Dogbane.