Thursday, August 30, 2012

Jewelweed - species profile

What: With my last post on poison ivy, I wanted to return to another good friend of mine: jewelweed (Impatiens capensis). In Centennial Woods, we only have spotted jewelweed (the yellow-flowered pale touch-me-not is found on much richer sites). I spent some time observing it while watching the hummingbirds, admiring its simple elegance. The flowers are so rich and ornate, with no shortage of suitors begging nectar. It grows abundantly anywhere there's water so I headed down into Centennial Woods below the sandy slopes and found a great patch to take some photos.

Ecological notes: Much like raspberry stems and boxelder twigs, the stalks of jewelweed have a weird white powdery bloom to them. I still have no idea what the function of these is, so if anyone knows, send me an email! I was told that it was yeast, but some sources say that this is just a myth wine makers false propagated. I would assume it might then have something to do with resistance to predation by insects or maybe it's a fungicide or for preventing water loss? Researchers in Osaka found that the bloom, at least on grapes, is oleanolic acid. They link it to preventing dehydration. Since jewelweed grows in intermittently wet areas, the bloom could prevent the plant from losing water in droughts (like right now) and thus maintain the stem's rigidity. Sounds reasonable. But why would boxelder twigs have the bloom?

Minute hairs on the surface of the leaves trap air and cause water to bead on the surface. When you hold a jewelweed leaf underwater it seems to transform miraculously into silver! These leaves were holding some of that much needed rain from last night. Many other plants do this too, and since it's a pattern we have to have a super cool esoteric word for it: superhydrophobicity (really afraid of water!! aka the lotus effect). Some plants achieve superhydrophobicity by having a dense coating of bristly hairs, others, like lotus, have waxy cuticles. Supposedly this is linked with both water retention as well as being able to wash leaves clean, even with dew. Since the water beads up it has a high internal charge and will pull dust and other stuff off the leaf surface. 

Yesterday I was noting that many had the malformed flowers, or galls. Inside that green blob there's a Jewelweed gall midge (Schizomyia impatientis). They hatch early fall and overwinter as adults. 

Where: There's a great patch of the spotted kind in CW where an intermittent stream drains off the slope (it's been dry most of the summer though) and you can follow the flow of the water by where the jewelweed grows. Jewelweed definitely prefers wetter areas. So when you find poison ivy, often times walking downslope or finding a drainage will yield a good patch of jewelweed.

Other notes: Jewelweed is pretty easy to cultivate. It's herbaceous, so it dies back every year, but it has perennial roots so it shoots up from the same spot each year. The seeds are spring loaded so when you touch them they erupt out from the pod (see the image of a swollen pod above). They're just now ripening. Seeds taste like walnuts and they've got about 3-5 per pod. Because they shoot so far they'll easily colonize a nice little patch. Ask Zac to see his jewelweed garden started from a single plant!

Tuesday, August 28, 2012

Poison ivy

What: Above is an amalgamation of 23 photos I took of poison ivy leaves (the three leaves are actually leaflets and collectively form a single leaf). I then put the transparency of each image at 1/23 to get the final result. I got the idea from visual artist Jason Salavon. I've been really interested in the diversity within a species, particularly since everything at this time of year is so abundant. It started with toads (will post a series of photos of them) but turned to poison ivy.

Yesterday I was out with my UVM class, Natural History of Centennial Woods, and we were taking a closer look at poison ivy (Toxicodendron radicans). I'm not a big fan of the "leaves of three let it be" mantra as it prevents people from actually looking at the plant. Besides, strawberries have 3 leaves, as do boxelder, clovers, some Virginia creeper, sarsaparilla, and heaps of other delicious and beautiful plants.

To avoid confusion and cement an understanding of what poison ivy looks like, we created a list of features that would help us distinguish it from other plants. Here are some of the ones I can remember:

  • Woody stem
  • Three leaves
  • Often has toothed edges to leaflets, rarely smooth (or entire)
  • Fades to a dull yellow 
  • Vines have "hairs" on them (see image below)
  • Middle leaflet has longer petiole (what attaches leaflet to stem) than two side leaflets
  • Middle leaflet symmetrical, lateral ones asymmetrical
  • Two leaflets on side look like they're giving the thumbs down

Ecological notes: Also of note on the poison ivy leaves were an abundance of poison ivy leafminers (Cameraria guttifinitella) that appear to be eating the upper layer of cells on the leaves. A couple years ago I watched a catbird eat the berries from poison ivy with great relish. I've seen rabbits nibble leaves, and apparently plenty of other animals will eat the plant and be unaffected by urushiol, the toxic oil in the leaves, stem, and buds that cause us such great irritation. So just because you see an animal eat something doesn't mean you can (particularly don't try and learn which mushrooms to eat by watching red squirrels).

Where: Centennial Woods, and any moderately rich, well-drained but moist soil near you.

Thursday, August 23, 2012


Female ruby-throated hummingbird (note white tips on tail)
Female ruby-throated hummingbird (note white tips on tail)

Visiting purple loosestrife
What: The second half of the last post is a delightfully little bundle of energy! Ryan and I had headed down to the powerlines after Jon told us about how many hummingbirds there were. I have been waiting for the spotted jewelweed (Impatiens capensis) to blossom, as each summer around mid/late August we get a flush of ruby-throated hummingbirds (Archilochus colubris) feeding on the nectar.

Ecological notes: Any hummingbird gardening guide lists jewelweed as a must (apparently ruby throated hummingbirds prefer spotted jewelweed to yellow jewelweed, I. pallida). Bumblebees and some butterflies also visit jewelweed flowers, but they're not nearly as effective at pollinating the plant, indicating that an evolutionary relationship might exist between the morphology of the flower and the feeding behavior of hummingbirds. I found some interesting notes about the relationship between the two, with unsupported claims that the weak petiole of the flower allows the plant to bend away from the hummingbird's advances, thus protecting the plant's ovaries from the long sharp piercing bill of the bird. Problem is that the complex shape of the flower places the ovaries at the back of the flower, well out of reach of the bird.

Research out of UMass Amherst indicate another, more likely possibility. Jewelweed flowers have flexible pedicels (stems) that allow the flower to bend readily. When feeding, hummingbirds flick out their tongue to slurp out the nectar. Each time the bird does so the weak pedicel allows the flower to recoil back in response and before flapping back forward. As it springs forward the flower dusts its pollen across the upper bill of the bird. It all happens in a brief second, so it's difficult to observe, but the tight relationship is enough to ensure successful pollination. To test this relationship, the researchers immobilized some flowers by wrapping wire around their pedicels. The rigid flowers were far easier for the hummingbirds to suck nectar from (visits were 25% shorter to these flowers), but significantly decreased pollen transfer (by about 50%). They also found that the stems of the flower didn't move when visited by bees, indicating that this is indeed an adaptation specific to hummingbird foraging behavior.

According to the researchers, there may also be a link between the shape/size of the spur (the hook at the back of the flower) and which pollinators (bees vs. birds) go after the individual flower.

Where: Centennial Woods, powerline

Other notes: Summer is coming to an end - you can feel the first crisp coolness of the night air. Queen Anne's lace is going to seed, morning glories and bind weed flowers are out in full force, fruits are ripening (go harvest wild grapes!), Jerusalem artichoke is flowering, and the birds are getting antsy ready to head south.

Tuesday, August 21, 2012

Dew this morning

Sunlight filtering through pines/red maples

What: Ryan and I went on a Centennial Woods wander early this morning right as the sun was coming over the Greens. The grass soaked our feet, and everything under the powerlines was covered with dew; a steamy mist was rising up from the ground and the forest had a beautiful glow.

Sunlight filtering through pines in Centennial Woods powerline cut

Ecological notes: We had really warm weather yesterday (in the 80s, and an afternoon rainshower) and it was relatively warm at night, cooling significantly by about 4am. Dew forms when heat radiates off an object and moisture in the air condenses out as it cools (like when droplets form on a cool glass of lemonade). The rate of condensation has to be quicker than rate of evaporation. So you wouldn't expect to get dew when:

  • it's windy (increased rate of evaporation), 
  • dry (not enough moisture to condense out), 
  • there's little difference in temperature between the surface of an object and the air
  • when it's super sunny or when it's cloudy
This is why dew tends to form in the morning or evening under a cloudless sky without wind. Dew is a common late summer phenomenon when days are warm and nights cool. But because the ground is so warm in the late summer, things directly touching the ground don't have dew on them. On the other hand,leaves, my windshield, and other exposed surfaces do get dew.

Dew on unopened chicory flowerDew on mugwort flower buds

Where: Centennial Woods

Dew on Phragmites leavesDew on Phragmites leaves

Other notes: The jewelweed is in full bloom right now, providing some wonderful late season nourishment for bees and hummingbirds.

Dew on bumblebee and spotted jewelweedAptly named birds nest (Queen Anne's lace)

Monday, August 13, 2012

Harvesting Honey

What: Callan, Zac, and I suited up and checked in on our hives. A few weeks ago we added supers to the hives and were hoping that the time for harvesting was finally here. And indeed it was! We gave one of our hives a headstart by giving it drawn out comes at the beginning of the season, and the upper of its two supers was completely drawn out with capped honey and no brood. The super probably weighed upwards of 30 pounds! The video shows a bit about the harvesting process once the frames had been removed from the hive. Zac also shows off some wonderful natural history knowledge.

It was amazing to see how much honey we harvested relative to the size of the super. The ball jars are actually sitting on a deep, which is 9 5/8" deep, whereas the super we harvested from is only 6 5/8" deep (its total volume is only about 1.2 square feet). 

Ecological notes: A lot of the clovers are past their peak and the mints, late season squash flowers, and goldenrods are taking center stage. I've seen the first knotweed flower buds, which is among the last sources of nectar for honey bees before winter sets in.

Where: My backyard

Other notes: We got about 2.5 gallons of honey off of our first harvest. Last year we had an early and a late harvest off of one hive, totally about 5 gallons of honey. Hopefully we will be able to harvest honey from our other two hives this year if we get a good flush of nectar over the next few weeks.

Sunday, August 12, 2012


What: After returning from a 8 day trip in Alaska, I'm so grateful to return for the crescendo of summer buzzing through the trees and meadows here in Burlington. Last night Callan and I paddled from North Beach to downtown to listen to the Lumineers play a lakefront concert. Old Crow Medicine Show headlined and we could hear them playing in the distance as we headed back home. I think the clicks from the bats, chirps from the angle-wings, croaks from the green frogs, and zzzzzzipsss from the katydids definitely upstaged them.

Ecological notes: Most of these insects are hard to spot because they're making their noises from high up in the canopy or once you get close they go silent. Occasionally I spot one of the musicians on the ground. Today while walking to the farmer's market I was lucky enough to find a pair dog-day cicadas (Tibicen sp., perhaps T. canicularis) locked together in their nuptial celebration. Lamely, I'm not sure but I think the one on the left is the female.

I took the below photo on May 11th this spring, in which you can see the smaller male copulating with the female - this is a derived behavior, as a primitive characteristic is to have the female on top. Not surprisingly, it's both intriguing and somewhat repulsive at the same time; I can't quite seem to figure out why some insects mate in this position while others like the cicada lock in a position facing away from one another - if anyone knows, please post a comment. I don't claim to be an expert on insect sex (see Dr. Tatiana's Sex Advice to All Creation for that), but from what I can gather the male has a telescoping "penis" composed of an aedaegus, a structure that extends from the abdomen - the rear third of an insect - and an endophallus, which extends further to deposit spermatophores into the female reproductive tract. Insects don't have swimming sperm, but encapsulated spermatophores and so need to be directly deposited to the site of implantation.

Aptly named, the dog-day cicadas are among the later insects to start making their buzzy wing-flapping noises. The related periodic cicada (Magicicada sp.) has a life cycle that results in outbreaks over large geographic areas every 13 or 17 years, depending on species. Both numbers are prime numbers and probably prevent repeated overlap with any would-be predators that might be on 2,3, 4, or 5 year population cycles (a predator with boom populations every 5 years would only over lap with the periodic cicadas every 85 years). Dog-day cicadas appear every year (and are therefore also known as annual cicadas). Not coincidentally, annual cicadas are predated upon by cicada killer wasps, while periodic cicadas are not known to be predated upon by any wasps. To hear a sampling of Tibicen cicadas check out Insect Singers

Where: My backyard and all over Burlington. The image was taken on Latham Ct in the middle of the road and I found a couple of dead ones nearby.

Etymology notes: Dog days refers to when Sirius, the Dog Star is overhead in the sky, which occurs during late summer.

Monday, August 6, 2012

Carolina locusts

What: Just before leaving for Alaska, I was finding great pleasure in taunting the Carolina Locusts (Dissosteira carolina). It seems like any dry lot or gravely path has at least a couple of these every 10 feet or so that will just explode off the ground when you get close enough. While at rest they virtually disappear into the background - unless that background is a blue tarp - but when they fly, their black wings with yellow border stand out (in flight they superficially resemble mourning cloaks).

Ecological notes: Grasshoppers (Order Orthoptera) undergo incomplete metamorphosis (hemimetabolism). So rather than have four distinct life stages (egg, larva - like a caterpillar, pupa/chrysalis/cocoon, adult) as with animals that undergo complete metamorphosis (holometabolism), they have three stages (egg, nymph, adult). Note the different terminology - larva is for animals with complete metamorphosis, nymph for animals with incomplete metamorphosis.

Having distinct life stages allows for a species to partition up habitat between life stages (e.g. monarch caterpillars eat foliage, adults eat nectar) rather than compete for resources. Because nymphs strongly resemble adults (except having underdeveloped wings and no reproductive organs), they might compete for resources. Dragonflies and many other insects avoid this by having aquatic nymphs and terrestrial adults. We can add a new term here: naiad, which entomologists use to distinguish when a nymph will occupy a different environment than the adult. Grasshoppers and locusts, along with many other insects, don't partition up the environment in this way (called paurometabolism).

Each shed of the exoskeleton (called an instar) brings the nymph closer to sexual maturity. With Carolina locusts, they get larger and darker. The females will get larger than males (about 2.5" long). Despite the color changes, at each stage they are nearly perfect at blending in to their background. Perhaps the color change from nymph to adulthood forces them to find new backdrops with which to camouflage and avoid competing with other life stages in this way.

Camouflage is a method of concealment of confusion that allows an animal to avoid detection. There are generally three types of camouflage. Dazzle camouflage totally disrupts a predators judgement about the size, shape, speed, and distance of a prey. Much like this pinwheel, this pattern is disorienteering. A lion attempting to go after a zebra will have no trouble spotting a herd, but might have trouble picking out one from the pack and visually separating it from the other zebras. Military boats took advantage of this patterning in World War I and WWII.

An animal may also camouflage itself by pretending to be something that it isn't. I posted earlier about the beautiful wood nymph moth that conceals itself by mimicking bird poop. Animals that utilize mimesis take advantage of the fact that predators maintain search images for prey items, avoiding cuing in on things that are inedible, like twigs (e.g. walking sticks, geometrid caterpillars like inchworms), bird poop, thorns (e.g. thorn bugs), leaves (e.g. katydids), etc. Mimicry is similar, but here only a body part resembles something else rather than the whole body, like those big glowing "eyes" on the wings of a sphinx moth.

Animals may also use a disruptive camouflage technique, called crypsis, that makes an animal difficult to see. An animal can do this by having a coloration similar to the background, as with the Carolina locust, breaking up its outline, countershading (fish have dark backs, light bellies), or one of the coolest, changing colors, like our native gray treefrog (or is it green?).

The locusts are so good at this. I had not trouble spotting them while they were in the air, but as soon as they landed the game began: trying to spot them in the woodchips, sandy patch, or shadows of grass that they landed in. 

Where: Backyards everywhere

Other notes: While locusts, these aren't the species associated with plagues and/or catastrophic agricultural decimation. While common and widespread, they might only seem more abundant because we come into contact with them more often. They prefer dry, rocky/sandy waste places - where better to find this than a city!

Friday, August 3, 2012

Late season nesting

What: Last week I spotted a female robin (Turdus migratorius) bouncing around in the slippery elm (Ulmus rubra) at the corner of my house. It was so neat to watch because the bird almost had an architectural eye when looking at the tree. I imagined it looking at angles of branches, sturdiness of limbs, relative hiddenness of the entryway access to food and water. She investigated for quite awhile, bouncing every so often to a new vantage point to reassess the quality of her new domicile. I had followed her to the spot because I heard a male robin singing and I hadn't heard one in a while. When I went to investigate I saw the female in my driveway picking up nesting material and then dropping it (female robins alone build the nest and incubate the eggs). It was like she was doing a full inspection of the territory for quality of supplies and location. This week I checked in again on her progress and she is now sitting on some eggs (not sure how many yet, will report back later).

Robins nest made mostly of mud with
twigs, grass, and bark strips (Ruby Mtns, Nevada)
Ecological notes: Last year a pair nested on the light outside our neighbor's door, the year prior they nested on the floodlight on my garage and fledged three young. I was bummed this year when we didn't have any nesting robins for most of the spring. What a treat though to have this pair, and so late in the year too. Most birds are done nesting by now and have started flocking together in larger groups (Monday I spotted about 50 geese honking and flying towards the lake).

Robins can have two to three clutches in a year, so I'm assuming that this is the second or third for this female this year. In general male robins are a darker gray, with a darker patch of slate on top of their heads, females tend to be browner. Lots of sources I read just parrot other sources, so I don't know how reliable they are. Apparently males have more robust streaks on their throats than females, but I don't know how reliable this is since it's a relative comparison. I'm in out of town right now (the photos are a couple days old), but when I get back I'm excited to look closer at their throats. Since the females are the only ones that sit on the eggs, that should be a pretty easy thing to study. The one sitting on the  Males are definitely the only ones that sing though.

Where: My backyard

Other notes: Robins are one of three types of birds we have that use mud to build their nests, phoebes and swallows being the other two in Vermont. I've watched a robin dip a stick in mud and carry it to the nesting site. You can see in the above photo that the nest also incorporates twigs, grass, and strips of plastic. Phoebe and barn swallows are pictured below:

Phoebe nest made primarily of moss, (Shelburne Farms)
Barn swallow nest made mostly of mud and grass (Bread and Butter Farm)