Dec 19, 2011

hooded crane hubbub

Birdwatchers at the crane refuge on the Hiwassee River spotted a black crane with a white head among thousands of grey sandhill cranes December 13. Soon it was identified as a hooded crane, an Asian species rarely found in North America. In fact, the Tennessee sighting is only the third known occurrence in the U.S. The second was this spring in Nebraska, and the first the prior spring in Idaho (the bird in the photo).

Hooded cranes have escaped from captivity in the U.S., including a 2006 escape from an Idaho aviary. Three hooded cranes escaped in 2001, also in Idaho. Cranes can live long lives, spanning several decades. If one or more escapee survived, it is likely trying to find a flock and a mate among sandhill cranes it encounters, but it may be having trouble on one or both counts due to its appearance. This could account for the pattern of sightings.

North America has three crane flyways, an eastern route between Florida wintering grounds and breeding grounds near the Great Lakes, a Great Plains route between Texas and the northern plains and tundra, and west-of-the-Rockies flyway between Mexican wintering grounds and northern Alaska. If the Idaho, Nebraska and Tennessee sightings are the same bird, it has switched from the western to central to eastern flyway in the span of four migrations.

In winter, cranes are opportunistic, nomadic, and travel in flocks. On their breeding grounds, they break into pairs or small family groups, and individual birds return to the same nesting area year after year. Unless a crane has no family and no mate, it will be geographically loyal. Unmated birds are subjected to harassment, especially on breeding territory, and an unmated bird that looks different likely gets double trouble. This social pressure could explain how one bird could show up on three migratory routes in close succession.

It does not explain whether the hooded crane originally strayed from a Siberian flock on its own or with human assistance. An initial sighting in Idaho would be expected either way. The retreat of Arctic ice in recent summers has created more opportunities for Siberian flocks to come in contact with Yukon flocks. The wings of a captive bird would be clipped, so it would struggle to fly and keep up with other cranes until molting in a new set of feathers. It should also have leg bands, and the observed bird does not.

Is it the same bird? Is it a wild bird? No one knows for sure.

Nov 30, 2011

watching a fritillary evolve

The most abundant butterfly on Caribbean islands is likely the gulf fritillary. Its wings from above are rich orange with black spots, from below a dirty orange mottled with white spots that glimmer silver in sunlight. Medium-sized, these butterflies reproduce all year long on Caribbean islands and along the gulf coast. Each year they spread northward as spring warms into summer, each generation expanding their range, but the gulf fritillary can not survive a hard freeze in any form, egg, caterpillar, pupa or adult. When winter comes, the species range collapses back to its coastal core.

Most years, gulf fritillaries make an appearance in East Tennessee, and they may hatch a generation or two before winter sets in. This year they did well. I witnessed at least three generations, including an adult that hatched in November in my kitchen from a chrysalis on a plant brought in from the porch a few days prior. I don't know whether it would have emerged had it remained outside. I don't know whether it headed south after I released it, whether a bird gobbled it up before it got anywhere or what, but the day after it hatched, in good flying weather I set it free.

In early November, I saw a pair mating. The female surely had trouble finding a passionflower vine to lay eggs on, and her offspring likely starved or froze if they even hatched. They were this year's doomed generation of gulf fritillary.

These November butterflies were the last of 2011, but they were not the first. The fritillary that emerged in my kitchen was born in late August, part of a hatching that reduced a prolific, porchrail passionflower to bare vines as September progressed. At the height of the feast, black-spined, red caterpillars in all stages of growth covered the plant. The biggest eaters hatched in late September. Most faced a dwindling supply of leaves and cold nights, pupating later in the year if at all. Though at best a quarter of the caterpillars survived to form a chrysalis, we still ended up with a good dozen pupa hanging under the eave above the porch.

The first generation to reach Tennessee in 2011 arrived as July turned to August. They hatched a generation of fritillaries that fatted themselves on Tennessee leaves before laying eggs of their own. If the first generation's grandchildren had the good sense to fly south, their genes may have blended back into the core population in and around the Gulf of Mexico.

Is the gulf fritillary evolving an overwintering strategy? Is their range expanding due to climate change? Was their success in Tennessee this year merely stochastic? Yes to all three. Any traits that favor range expansion are likely to perpetuate and rise toward dominance, and stochasticity is always present because it is entropy. A yearly excursion northward is an overwintering strategy, even if a clumsy one. The gulf fritillary is evolving right before our eyes.

Aug 18, 2011

not a bird no more

A trove of fossils in China from around the time birds were evolving continues to yield insights into how feathers and flight evolved. Science still does not have a good story for the evolution of birds, but the cast of characters has gotten bigger. With so many new clues, Archaeopteryx has now been dethroned as 'oldest bird'. Birds came off the dinosaur family tree near Archaeopteryx, but not from its branch.

Recently National Geographic ran an article on feathers that summarizes much of the known fossil record, how it relates to the chain of ancestry and what it tells us about the evolution of flight.

At the time of Archaeopteryx, numerous dinosaur species had feathers or protofeathers, and evolutionary pressure was diversifying and selecting feather traits. Many animals clearly unable to fly possessed feathers, so they did not originate to enhance flight. Flight originated once feathers already existed.

The better story emerging from the fossils is this: flight evolved from swimming and diving. In their squabbles over whether birds flew from the ground up or down from the trees, scientists neglected this third option. Dinosaurs started entering water for prey, gradually evolving specialized scales with thermal properties and spending more time in the water. Their aquatic habits eventually included true swimming, which lead to the gradual evolution of larger and more powerful muscles and aerodynamic feathers. Swimming set the stage for aerial flight.

The origin of flight in birds is the story of the evolution of the breastplate to which a bird's wing muscles attach. This bone shows specializations seen only in birds, and flight muscles attach in a way that is essentially an inversion of forelimb musculature as it appears in every other four-limbed vertebrate including humans. We know that flying reptiles like Pterodactyls are unrelated to birds because they lacked an inverted musculature and large breastplate.

Birds have a muscle configuration all their own, and the wishbone is part of their unique skeleton. It is found only in birds and in dinosaurs like Archaeopteryx, Sapeornis and few others. While those fossils have wishbones, they lack large muscle-attachment sites on the breastbone and show no indication of significant strength in their forelimbs. So inverted musculature evolved prior to the origin of birds. It is not an adapatation to flight but a precursor.

Aerial flight requires strength, even just to glide. The power demand makes transitions from terrestrial to aerial locomotion unlikely, and the major retooling of the breastplate in birds is the sort of change that happens gradually, on geological time scales rather than generational scales. It is simply not reasonable to expect the evolution of flight to be as simple as the tales science has been exploring.

To understand the origin of flight, we need to think of a process taking many steps and millions of years, and the story should take place in water. Water is far more buoyant than air, so flying in water requires less power. We call that swimming. Gliding in water we call diving. An aquatic origin provides the time and opportunity for big changes in power and musculature. Diving lizards become swimming lizards, and shorelines become open waters. Eventually a master swimmer makes transition to aerial flight.

The oldest fossils that possess a bird's breastplate are the Hesperornithes, which resemble diving birds like loons. There are numerous marine varieties of birds, including albatrosses, ducks, gulls, pelicans and sandpipers, and they are deeply rooted in bird phylogeny. Terrestrial and forest birds arose later in avian history: fowl, hawks, songbirds, woodpeckers, these are younger varieties of bird.

Science has overlooked an aquatic phase in bird evolution, but it is staring us right in the face.

Jun 12, 2011

blackberry season

Right about now, your tomato vines need you to pick their first fruit so they will grow a dozen more. It is tempting to wait for the first red fruit, but foolish. A green tomato harvest is a must for a bountiful year. Do not succumb to red's seduction.

Instead, harvest a handful or two of the ripest blackberries you can find, toss them in oil with a chopped onion or leek, salt and a dose of dry spices. Cook to submission, then toss a layer of basil and other fresh herbs onto the pile and smother with green tomato chunks. Cook it down to a sauce. When the blackberry seeds are cooked, your sauce is done. They like it if you share your wine.

Serve the resulting sauce over pasta, fish, rice, tofu, tempeh, vegetables or meat, which you can toss into the pan if the sauce refuses to thicken. Happy green tomato season!

Jun 2, 2011

nest update

This morning the blue-headed vireos were vigorously defending their territory from a blue jay. Though it was much higher up in the trees than their nest, the pair was scolding and dive-bombing the jay, hoping to drive it off.

Unfortunately they may be protecting a young cowbird. The noise overhead roused a hungry nestling, just one, its eyes still closed. It seems too large already. Cowbird nestlings eject their nestmates, so seeing just one head is a bad sign. I checked the ground beneath the nest for evidence and found nothing, but such a morsel probably would have been found by a possum or raccoon on its nightly prowl. I fear my guests may be raising a chick that is not their own.

May 31, 2011

science for the fishies

If you've read anything about commercial fishing in the past decade or two, you know that industrial fishing practices range from irresponsible to appalling. The worst practices cause major seafloor destruction and grotesque slaughter of "by-catch," marine life ranging from rough fish to sea turtles. Over the past century, countless fisheries have collapsed under the strain of unsustainable harvest, leaving regional economies in ruins while the global industry trudges blithely to its next victim.

The anonymous fish flesh that you buy frozen and breaded in the supermarket or fast-food restaurant is the product of a shadowy industry where breaches of treaties, boundaries and quotas are routine. Even when a seller makes promises about the origin of a fish, their claims are unreliable and unverifiable, until now.

The Economist reports that a European consortium has developed a DNA-sampling procedure that can ascertain not only which species of fish a fillet came from, but which ocean and population. Right now the technology only covers four major commercial species: cod, hake, herring and sole, but its scope will expand.

The device is not intended for consumers at the end of the supply chain, but for those who buy in quantity. As a consumer, you can help by being curious about fish you buy and responsive to labeling or the lack thereof. This new technology is a welcome development that should bring some honesty to a market that has thrived on obscuring links between products and the sometimes horrendous practices used in harvest.

May 22, 2011

new yard nester

Red-eyed vireos nest in my yard every year. They are wonderful birds and welcome guests, but this year a different vireo seemed to be settling in the yard. I had heard it singing for a week, longer than migrants stick around, but I still did not tell anyone for fear of jinxing it. I thought a blue-headed vireo might be taking up residence!

Both species are common in the eastern U.S., but red-eyed vireos are more widely distributed. Blue-headed vireos prefer higher elevations and deeper forests. When I first came to the South, it was to study neotropical migrants in Nantahala National Forest, and blue-headed vireos were abundant in that rare place.

Aside from reminding me of a special time and place, they are charming in their own right. They used to be called solitary vireos, a terrible misnomer since they almost always occur in pairs, chattering at each other like an old married couple. The only reason I can imagine for their former name is the melancholy tone of their song. That same endearing expressiveness comes through in all their vocalizations.

Also, they look like they are wearing spectacles.

Today I saw their nest just a few yards from my front porch in the lowest limb of a white oak.

May 5, 2011

most courageous scientist ever

History is full of scientists who are heroes: savers of lives, solvers of mysteries, builders of the future. They are, however, a pretty nerdy lot, achieving great feats of the mind like wrestling with mathematical equations, dismembering molecules and exploding paradigms, but rarely performing physical acts of courage and strength. Then there is Ken Sims, volcanologist from the University of Wyoming:

"He didn't have a hammer, so with a hard slam of his fist he broke off a piece of fresh lava. It was shiny, iridescent black, and so hot that, even wearing thermal gloves, he juggled it from hand to hand.

But he had it. The zero-age sample. Through a war zone, up a mountain, down a crater, to the edge of a lava lake, he had it. Now the science, at long last, could begin.

Read the whole shoe-melting tale of Congo's Nyiragongo volcano at National Geographic.

May 1, 2011

successful journey

The white spot near the center of this photo is proof of a successful journey. It is an egg. The female that laid it flew some 1500 miles to get to the meadow behind my house, where she and at least one other monarch butterfly have been fluttering around for a week or two depositing eggs, one at a time, on butterfly weed and common milkweed plants.

Their earliest eggs have already hatched. This weekend I saw caterpillars so small they must have just hatched and a couple that looked like they've had a few good meals. They will eat for several weeks, molt several times, and eventually attach themselves to a leaf or stem with silk, form a hard shell over their bodies and begin metamorphosis into a gorgeous orange, black and white butterfly.

The monarchs flitting about my meadow right now are not so gorgeous. The wear and tear of their flight to and from the mountains of Mexico clearly shows.

Not only are the wing edges tattered, the scales are worn or absent, leaving dull colors. Though monarchs are talented enough flyers to glide on a breeze, she has undoubtedly flapped those wings millions of times. Her abdomen is bare. Despite her appearance, her attitude is pure butterfly: exuberant, whimsical and sunny.

Here she is laying the egg pictured above:

Her offspring with be beautiful and richly colored, and they will seek mates in the meadows of Blount county, lay eggs on the same milkweed plants, and their offspring will grow big, pupate, emerge gorgeous and undertake the journey to Mexico before freezing temperatures arrive. One or two will return next spring, as they have for millions of years.

It all starts with an egg and a tiny caterpillar that will probably never wander from its natal milkweed until it grows wings.

Apr 16, 2011

spare the tent caterpillars

Don't hate me because I infest your cherry trees. Don't hate me because I may eat every leaf on the tree. I will not touch a single flower, you watch.

The tree will grow a new batch of leaves and produce a full crop of fruits all the birds will love. Some of those birds will even eat me after bashing me to death on a twig to knock off my hairs.

If you burn my tents, everyone suffers, especially the guilty. Me and the cherry trees made a pact a long time ago; who the hell are you?

Apr 5, 2011

post-flood spider web update

My friend Andrei noticed a link under one of the National Geographic photos that I had overlooked. It described a similar phenomenon at a park in Texas in 2007. During a wet period and an outbreak of midges and other aquatic and semi-aquatic insects, a tree near Lake Tawakoni became completely enmeshed in spider silk.

An arachnologist collected about 100 spiders from the webbing and identified species from 11 different families. The dominant species was Tetragnatha guatemalensis, a fairly common spider distributed throughout the Americas. This family, common name being long-jawed orb weavers, is riparian, typically building horizontal orb webs over water. They exhibit colonial behavior, tolerating neighbors to the extent of sharing thick, foundational silk strands within which they build their daily orb web. None are truly social. Their typical web looks nothing like the sheet webs covering these trees.

Research has shown that spiders' aggressiveness diminishes when food is plentiful. In flush times, it's common for a web-building spider to catch more prey than it can consume. What may have happened in Texas and Pakistan is floodwaters drove spiders whose normal habitat is edges of streams and rivers to refuge in trees. When rains subsided and the spiders began to seek places to build webs, flying insects were in such abundance that simple drag lines served as adequate traps. Instead of going to the trouble of constructing orbs, they just wandered around, leaving silk lines as all spiders do, too sated to bother with risky, aggressive interactions with other, similarly situated spiders.

The end result was a huge, disordered mass of silk covering entire trees and shrubs.

Apr 1, 2011

post-flood spider webs

National Geographic published this photo of trees covered in spider silk in Pakistan. This area was ravaged by major floods last year, and as waters receded, these trees became one giant web.

According to the article, floodwaters "drove millions of spiders into the trees," but this is highly unlikely. For starters, most spiders are not at all social. Another spider is just something to attack and eat. A tree full of stranded spiders would be a scene of carnage. Secondly, spiders build many different types of webs, but each species builds in a distinct style. These trees are almost surely colonized by a single species, not a collection of flood refugees.

There are a few species of social spiders, even one that occurs locally. I've seen their webs along Third Creek. They build a messy glob of silk most spiders would be ashamed of on branch tips over water. They look like the work of caterpillars, and these photos look like cherry trees infested with tent caterpillars.

The article includes no photos of the spiders, but I'm sure NatGeo is reliable on that account. My guess is these webs were built by social, riparian spiders. Rather than being driven to the trees by the flood, colonies probably experienced a population boom feasting on flies that feasted on the detritus of the flood.

luxury jets

I've long suspected that exhaust from airplanes, by virtue of being released high in the atmosphere, is more problematic than exhaust from cars and trucks. A new study in the prestigious journal Nature confirms that air travel causes more climate disruption, but not for the reason I imagined.

It turns out that condensation trails, or contrails, trigger formation of cirrus clouds much like those which form naturally. Cirrus clouds are high, thin and wispy, and they appear when moist air meets temperatures cold enough for ice formation. These clouds trap heat in the atmosphere, and the authors estimate that short-term warming from contrails is about equal to long-term warming from the plane's release of carbon dioxide. The climate footprint of air travel, therefore, is double what you'd calculate looking only at fuel consumption.

More study is needed to fully understand the climate impacts of jets, but it's safe to say that we need to view air travel as a luxury, not a convenience. In a gluttonous age, routine air travel may be our biggest indulgence.

Mar 29, 2011

pinkish gray

Though spring has just arrived, winged elms are already in seed. Orangish when they flowered in February, elms are now encased in a vaguely pinkish gray. When the seeds mature, they will dry and grow brittle enough to break from the twig in a wind. A shape not unlike a boat's propeller makes the oval seeds spin as they descend, keeping them aloft good distances from the parent tree.

Elm seeds also drift into piles like snow.

Redbuds are at the height of color, oaks dripping yellow with flowers. Tuliptrees are bringing an exuberant green to hillsides. Right now you can tell almost every species of local tree at a glance from its color and stage of growth. Maples, like elms, are growing seeds.

Most native trees flower first then leaf out, but a few grow leaves first. Every species has unique timing and sequence, and once you learn to notice, you can learn which is which. Some grow seeds right after the flowers fall off, others spend months growing fruits or nuts that mature in summer or fall.

Two of the main groups that have not yet broken bud are hickories and ashes. Both are about to go. They leaf and flower simultaneously.

Mar 3, 2011

bringer of butterflies

When cutleaf toothwort pokes through the leaves, falcate orangetip butterflies are not far behind. They are the primary native pollinator, a small white butterfly whose orange is but a blur. Falcate orangetips rarely spread their wings while perched, showing only the mottled grey underwings.

A glimpse of their orange is a treat, and sitting amid toothworts for a few minutes is your best approach. When they perch, their weight is enough to jostle the flower. They flutter while regaining balance, and occasionally the wings don't fold up all the way, leaving the orange exposed.

I thought I would see one last weekend, but I only saw a mourning cloak and a question mark. I had to dig up a falcate orangetip photo from 2008.

These butterflies are close relatives of sulfur, cabbage and white butterflies, Pierids. One of the more speciose local families, more than a dozen species may be seen in Southern Applachia, most are a good bit larger than toothwort's friend.

Feb 26, 2011

they're here

Toothworts sprouted today. Most have a good bit of growing left before they flower, but that will not take long while the days are as warm and bright as today. Soon our woods will be sprinkled with a pinkish white that is the starter's pistol on the wildflower bloom, cutleaf toothwort.

Sure, bloodroot and hepatica can emerge earlier, but their appearance does not foretell spring like Dentaria laciniata. Bloodroot and hepatica are hard to find, whereas toothwort is all over the place. It is the uncurling of their stalks that defines the start of spring, and it was today.

Feb 20, 2011

unexpected nature

Ten Mile Creek runs through the heart of West Knoxville's sprawl, accompanied in segments by a paved greenway. Today I hiked there, and I found it clogged with privet and bush honeysuckle to the point that little else grows. The canopy is native trees, but much of the understory is invaders. Native vines have been crowded out and replaced by honeysuckle and bittersweet.

Recent construction has respected the creek more than a few older developments with flat grades and rubble piled to the lip of the creekbed. Such earth moving restricts the floodplain, raising floodwaters. Sprawl's parking lots, rooftops and roadways allow less rain to soak into the ground. Instead, it finds its way quickly to creeks, which overtop their banks more often.

Scouring along Ten Mile is a culprit in the absence of biodiversity. Much of the seed bank that might have restored native plants after construction was washed away in sprawl-exacerbated floods. The sprawlyburbs are flood-prone by design. That is why it is comforting amid all that ecological damage to see life persevere.

Ten Mile Creek Greenway curls between a fence and an artificial cliff at the edge of the Sam's Club/Walmart complex. The cliff is constructed of wire-baled rocks, but the trees below were not cut, so large tulips, sycamores, hackberries and others butt up against the fake cliff. Below that fence and through the woods, a wetland remains, and I saw ducks in the water.

I stopped to look through binoculars and found two pair of mallards feasting on aquatic plants. I heard a rustling from the leaves on the other side of the fence, looked down and discovered a hermit thrush flipping leaves and hopping toward a rusted shopping cart of uncertain age. Around the next bend I stopped to scan the wetlands from another vantage point and noticed a lump on a limb overhead. It was a sleeping raccoon curled into a cradle of tree limbs.

Nearby I saw a Cooper's hawk fly up from the creek to a low perch. It was probably cleaning itself after devouring a small bird. A few native alders linger in the sea of privet.

Feb 2, 2011

fooling a heron

After a delicious lunch at Sweet P's BBQ on the Stock Creek embayment, I wandered over to the water to see what was around. A song sparrow lurked in the weeds, but mostly I saw great blue herons, about a dozen. Most had staked out a hunting spot, and the few that had not were squabbling over turf with swoops and squawks.

Then the gulls moved in, at least a hundred ring bills. They glided over the water and soon began diving en masse into the water with vigorous plunges. A nearby heron had the same thought I did: they are after fish. The heron excitedly ambled out into the water, right into the center of the flock of gulls, but there were no fish. After a few indignant moments amid plunging gulls, the heron returned to its spot.

I snapped a bunch of photos at the fastest shutter speed the overcast day would allow, and upon inspection I could see the gulls were hitting the water feet first. Gulls have webbed feet, not talons, and when they pluck fish from the water, they grab them with their bill. My guess is the gulls were taking a bath. I'm not sure what the heron thought.

Jan 26, 2011

sky behind a sycamore

No native tree is as easy to recognize as the sycamore. Its bark peels in unique ways, leaving smooth white branches and trunks that can not be mistaken. Sycamore trunks and branches curl and twist. In moonlight sycamores glow; in sunlight they offer odd shapes and shades of of green and brown.

An animal you would never suspect of using camouflage: huge, mint green luna moths, wings edged in thick purple with tails and eyespots, vanish against sycamore bark. Sycamores are most abundant along streams and rivers, happy with wet roots, thirsty, and the flush of spring turns their white bark green. Moths the size of your hand can be next to invisible perched on a sycamore.

Sycamore wood burns poorly and is difficult to cut and mill. With little productive value but an ability to stabilize streambanks, sycamores are often left alone when land is logged or cleared for pasture or development. Even where most trees are gone, majestic old sycamores might remain, doing no one any good except luna moths, stream dwellers and whatever depends on stream and river water being clean.

Jan 1, 2011

lichen this

It was one of those beautiful days when everything is wet. Between wind, rain and fog, moisture creeped in every crevice from all directions. Water being that which merits the most gratitude, I see wet days as beauty, though they break limbs and topple trees. Mist feeds things like mistletoe and lichen. Water is a rare delicacy they savor, and when they get a drink on a new year's first day, it is cause for celebration.

Against wet bark, lichen glows brighter than normal. Flat, winter light and exaggerated contrast bring pale lichens to prominence, but it may not just be wet bark at work. Lichen may actually glow brighter in wet, winter weather.

Lichen is a symbiotic pairing of algae and fungus, the original pioneers of dry land. Long before there were trees, flowers or fields of grass, algae and mold grew on a stark landscape of rock, sand, dirt, but nothing that could be fairly called "soil." Soil is an end result of biodiversity, not its ancestor. Algae, moss, molds and mycelia don't need soil; soil is the graveyard of their proliferation and evolution.

Lichen likely predates most or all terrestrial plant and animal life, and a warm, wet winter afternoon may remind it of the stark, ancestral Earth where algae and mold first partnered. It may glow mint-green and grateful against gray bark.