Category Archives: Fruits

Red (white and blue) carpet for migrant birds

They’re forest beacons, glowing come-hithers to migrant birds. These gene catapults, each carrying a plant’s hope for another generation, are ripening this week in Sewanee and across the eastern US. Not coincidentally, thrushes and other south-bound birds are also on the move (see BirdCast for the feathered forecast near you).

Some fruits from the woods near Sewanee:


Ghosts rise from forest duff

2015-07-13 indian pipe monotropa 018Ghost plant, Monotropa uniflora, is now flowering in shaded woodlands. The species is also known as Indian pipe or corpse plant. Each stem is about finger-high and has a nodding flower at its tip. The plant’s pallor tells the story of its peculiar feeding methods. Rather than using pigments to gather sunlight, the roots are sheathed with fungi from whom the plant gets its food. Monotropa is quite specialized, connecting to a small number of Russula fungi species. The fungi in turn feed themselves by tapping the roots of trees, so Monotropa is indirectly feeding from other plants, using a fungus as the money-laundering intermediary. Whether the fungus gets anything in return from Monotropa is not known. The plant is usually regarded as wholly parasitic.

2015-07-13 indian pipe monotropa 009Monotropa belongs to the Ericaceae plant family, a group that includes heathers, blueberries, rhododendron, and sourwood. These species often live on nutrient-poor acid soil where symbiotic relationships with fungi help the plants to thrive in conditions that are otherwise hostile to roots. Monotropa also favors acidic areas and is often found in deep shade under conifers. It seems that Monotropa took its family heritage and changed it from mutualism to piracy. If so, this is the genus that no-one likes to discuss at the Ericaceae family reunion. Quite why the fungus would put up with its parasite is a mystery. It could be that the evolution of defensive mechanisms has not happened because the tiny Monotropa plant draws so little food compared to the supply that the fungus receives from trees. It is perhaps no coincidence that nearly all non-parasitic Ericaceae plants are shrubs and trees, and only Monotropa is a tiny sprout. The plant’s narrow range of fungal associates may also indicate that only a few fungus species can be fooled. All this has conservation implications: Chris Martine and Alison Hale have recently published a fascinating article suggesting that chemicals from invasive plants such as garlic mustard may disrupt the relationships between Monotropa and its fungi, causing population declines.

The species lives in North America, Asia, and Central America, with large geographic gaps between each population. Recent studies of DNA show that these populations have diverged from one another and have distinctive genetic signatures, suggesting that they might best be regarded as different species. How the species came to have such a distribution is unknown: the dust-like, winged seeds may have traveled by wind or the distribution may be an echo of the ancient geographic connections among these continents.

Five days after the bloom pictured above, pollinating bumblebees have done their work and the red fruit capsules are swelling. The flower’s rain-shedding, bee-welcoming droop has straightened and the fruit points directly to the sky, presumably the better to catch some favorable winds to a neighboring uncolonized fungus, or to Japan.

2015-07-18 monotropa fruit 002

Snow graphemes, scribed by plants

Fallen leaves and fruits etch the snow when caught by the wind, leaving inscrutable messages. Tree roots do the same as they carve up through asphalt. The last few weeks have provided ample opportunity to read these signs.

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These snow scribblings bring to mind David Hinton’s description of the work of the Chinese poet Summit-Gate (峰門). Summit-Gate would gather particularly beautiful autumn leaves and carefully lay them in book-scroll boxes. These boxes were her library. When snows came, she took the leaves to her poetry shelter and released them one by one, watching their wind-blown botanical calligraphy on the snow. She could read the start of every poem but, by choice, the conclusions eluded her.

There is more to her story, all told in David’s excellent book, Hunger Mountain, a meditation on landscape, mind, and literature.

So in these snowy days, we can learn from Summit-Gate and keep our eyes on the surface to see what legumes, samaras, and cast-off leaves might be saying. Ideograms are also being continually made and erased on other surfaces: beaches, dusty roadsides, perhaps even the ooze on a scummy lake. This is “tracking” of a different sort.

Mayapple fruit

On a recent walk in Shakerag Hollow I ran across this mayapple (Podophyllum peltatum) plant lying prostrate on the ground, its fruit resting on the leaf litter surface. This is box turtle food. Turtles love the fruits and serve as seed dispersers for the plant. The fruit is the size of a small lemon.

Mayapple contains chemicals that are used in anti-cancer drugs, so our health depends, in small part, on the ecological services provided by box turtles. One more reason to drive carefully? I moved this fellow (red eyes, domed plastron = a male) out of the way last week…

Celandine Poppies

On my return to Sewanee, I made a trip down Shakerag Hollow to see whether I had missed the blooms of my favorite spring flowers, celandine poppies (Stylophorum diphyllum). These are short-lived flowers, easily damaged by rain, a fragility that somehow makes them all the more compelling.

Most had set seed already, with hairy pods hanging below the leaves.

But a few flowers remained. This is one of the few yellow-flowered species in the spring (in this patch of woods, they are the only one).

Ants play an important part in the life history of this species. The small fruits that fall from the pods have large ant-attracting food packages, elaiosomes, attached to them. The ants drag off the fruits, eat the attractant, then discard the fruit. In this way, the poppy seeds are “planted” in the good fertile soil of an ant waste heap. Thank you, ants.



Waxwing invasion

Flocks of hundreds of cedar waxwings descended on Sewanee this week. They travel in nomadic groups, searching for sugary fruits. Unlike most birds in our region, waxwings feed almost exclusively on fruit for much of the year. In Sewanee, they are sporadically common in the spring and fall, but very scarce in summertime. Most of the birds that are here this week will move north and east to breed. Look for them perched in tight clusters in the treetops or fluttering around fruiting shrubs.

The waxwings’ high-pitched calls (up to 8kHz, nearly twice as high as the highest piano note) are distinctive, but they test the limit of our hearing. For many people, the calls are inaudible except at close range when the sound gets loud enough to cross the ears’ detection threshold. As we age, we naturally lose hearing in the high range, although this can be accelerated by exposure to loud noise (earplugs are a naturalist’s best friend…).

Waxwings are named for the tiny red “flags” on the end of some of their wing feathers. Although these little flags look like wax, they are made of the same material, keratin, as the rest of the feather, infused with red pigment. Young birds have fewer flags, so these red marks may act as social signals through which older birds can avoid breeding with inexperienced youngsters. Older birds have higher breeding success, so it is to their advantage to stick together.

The yellow bar across the end of the waxwings’ tails is also produced by a pigment in the feathers. Over the last forty years, waxwings with orange-banded tails have appeared, especially in the north-eastern parts of the continent. At first, scientists speculated that this was a new mutation, spreading through natural selection. Further study showed that no genetic change was involved. Instead, the waxwings were feeding on the fruits of an invasive plant, Morrow’s honeysuckle, that contained orange pigment. If a molting waxwing feeds on this honeysuckle, the new feathers will pick up the orange pigment. In addition, all the fat in their bodies gets stained. I think of waxwings every time I see someone sucking on a blue slurpee. Surely their insides must be turning blue; maybe the hair will follow.

The photos on this page show the various ways that the waxwings use their silky crests to signal to each other — flat, cocked, and spiky. This expressiveness, combined with their eye-bands and overall silky plumage makes them one of the sharper-dressed birds in our region. Classy.

My account draws on information in: Witmer, M. C., D. J. Mountjoy and L. Elliot. 1997. Cedar Waxwing (Bombycilla cedrorum), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology. doi:10.2173/bna.309  The lead author on this paper is Mark Witmer, a colleague from grad school. He showed me the orange insides of a waxwing once — very cool.


This lonesome old tree by the waterline has a special visitor perched at its top: a merlin visiting from Northern Canada. Merlins (Falco columbarius) are small falcons that breed in the boreal forest. They are uncommon winter visitors to our region. We found the bird at the end of our class visit to Crow Creek Wildlife Refuge near Stevenson, AL.

Merlin, condensed to about 2 pixels. Great views through the scope, though.

Merlins are spectacular little birds. They sit and wait for an unsuspecting songbird to fly past, then they explode into rapid flight and chase down the prey, catching it in midair. They are the fighter jets of the bird world: fast, maneuverable, and uncompromisingly fierce. “…no falsifying dream/Between my hooked head and hooked feet”.


The warm weather turned up some other unusual phenomena: great-blue herons standing over their big stick nests, maples in bloom, and chorus frogs singing. This is a very peculiar January — prolonged warm weather has unlocked all kinds of activity that in normal years would not happen for another month.

Red maple flowers...on Jan 31st

In summer, the water in the Crow Creek Refuge is carpeted with the large round leaves of American Lotus (Nelumbo lutea; also called Water Chinquapin). Now, the plants are invisible (their stems are underwater in the mud) except for the strange seed receptacles that litter the shoreline like organic showerheads.

Seeds fit inside the holes on the top surface.

We also found a rare specimen of Florus plasticus washed up on shore.

The pollinator of this flower is unknown, but it probably requires a battery.


A single mistletoe plant is growing near the top of an ash tree behind Shenanigans and Woody’s Bikes. Mistletoe is not common in Sewanee, although it can be quite abundant on the lower slopes of the coves.

American mistletoe, Phoradendron leucarpum (literally, the "white-seeded tree thief")

Recently, biologists have realized that mistletoe is a very important part of the ecology of forests. In fact, mistletoe has such a major effect on other species that it has been called a “keystone species,” one of the major determinants of a forest community’s vitality. How so? Mistletoe steals some of its host tree’s food and combines this with the food that it makes for itself through photosynthesis. This combination of a big trust fund (the tree) and a steady job (the mistletoe’s own leaves) allows the plant to live large, offering abundant nectar in the early spring and fat, nutritious fruit later in the year.

Bees love the nectar which comes earlier in the year than the nectar of most other flower species. Birds and many climbing mammals adore the fruit. The pulp of the fruit is sticky, ensuring that it will stick to branches after it has passed through the bird. More, the seed is often so gummy that it sticks to the birds’ feathers. Birds have to grab the seed, then wipe it off on a branch — a perfect way for the mistletoe seed to get placed exactly where it needs to be. So, this small plant is used by dozens of invertebrate and vertebrate animals. One butterfly, the great purple hairstreak, has gone so far as to become wholly dependent on the plant. Its caterpillars will eat nothing else.

In other parts of the world, including the western U.S., different mistletoe species provide a similar range of services. Some even provide favored nesting areas for many birds. A review of mistletoe biology a few years ago stated that, “…the widespread perception of mistletoes as destructive weeds needs to be challenged. Many landholders, managers, and even biologists regard mistletoes as invasive pests, damaging to individual trees and detrimental to forest health. [But] …mistletoes have a substantial positive role in many forests and woodlands, and should be given appropriate recognition.” (from: Watson, D. M.. 2001. Mistletoe — a keystone resource in forests and woodlands worldwide. Annu. Rev. Ecol. Syst. 32:219–49)

Of course, mistletoe has other roles in the ecology of our world. So, I’ll sit and do my end-of-semester grading under the thief, ever hopeful that songbirds will visit.

Autumn, part 2, begins

A vigorous killing frost laid waste to the last of the tender summer plants in the vegetable garden.

RIP squash vines

I harvested the last of the peppers before they could get zapped,

then planted garlic bulbs in the empty pepper beds.

New birds in the garden today, all refugees from the north that will stay with us for the winter: dark-eyed junco, yellow-bellied sapsucker, and white-throated sparrow.

Pileated woodpecker feasting on magnolia fruits

The sun was rising directly behind the magnolia tree

Southern magnolia (Magnolia grandiflora) fruits are dyed bright red by lycopene pigment, the same colorant that gives tomatoes their glow. They are buried in the brown husk at the bird’s feet. Like other colored autumn fruits, the magnolia is advertising its wares to passing seed-dispersers.

Across the road, the male’s mate was pecking at a dead tree trunk. After a minute or two, she flew down to join him at the fruit bar.

Note her black mustache and black forehead (the male has red in both places).