City Creek Nature Notes – Salt Lake City

May 6, 2017

May 2nd

First Dragonfly

4:00 p.m. For the first half-mile, cottonwood trees all have inflorescences, but at picnic site 1, there is one with one inch leaves. Box Elders are leafing out and providing the beginnings of shade. Red ozier dogwoods have two inch leaves and now look like a true bush. The same occurs for Woods rosa. The first quarter-mile of the road begins to look like a green tube. The stream runs three inches over the top of the rocks that makes the pond at picnic site 5, but it is also three inches below its highest mark on the Zen Rock.

I see the first dragonfly of the season: a reddish-brown about three inches long; it is an immature Variegated Meadowhawk. In the canyon today, there are two examples of the White-lined sphinx moth. A Western tiger swallowtail (Papilio rutulus) swims by with its bright yellow wings flashing under the sunlight.

Bicyclists dominate the road. There are over forty in groups numbering between two to eight riders. They speed down the road, and although I am on the right-side of the road, one misses me with an emergency skid and tack maneuver.

* * * *

On May 2nd, 2008, the Utah Rivers Council plans to hold a clean-up of City Creek Canyon’s stream bed (Deseret News). On May 2nd, 2007, the Utah Rivers Council plans a stream clean-up in City Creek Canyon (Salt Lake Tribune). On May 2nd, 1910, A. B. Sawyer, owner of the Little Giant Mine in City Creek, sought a lease from the city to construct a boarding house for miners 12 miles up the canyon in order to work a mining claim (Salt Lake Herald, Salt Lake Telegram). On May 2nd, 1899, the City Creek Canyon water patrolman put out a fire caused by an abandoned camp fire (Salt Lake Tribune). On May 2nd, 1897, the Salt Lake Herald suggested City Creek Canyon as a site for May day picnics.

November 9, 2016

November 9th

Filed under: Gambel's Oak, gnats, Insects, moss, Plants, Variegated Meadowhawks — canopus56 @ 6:09 pm

Ghosts in the Canyon

9:30 a.m. As I run up-canyon, the morning cold is still on the road. Coming down canyon, the Sun hits the road in the lower canyon and a few gnats have begun to rise. Gnats, small non-biting flies, live off the moss that grows profusely in the stream and rotting vegetation at its banks. In the afternoons, there are still one or two Variegated Meadowhawk dragonflies, but they are not enough to keep the gnats down. In this season’s colder weather, gnats like to stay in the warming sunlight. On November 4th at 5:00 p.m., backlit by the sun’s rays, I estimated that there between 200 and 300 gnats near Guardhouse Gate. On October 31st, while running down canyon at milepost 1.5, the line of the setting sun was above 20 feet above the road. There were no gnats at the level of the road in shadow, but looking up into the backlit sunlight, I estimated about 100 gnats were following the rising sunline. Like Gambel’s oak acorns, the prolific gnats are another base of the canyon’s food chain. They are food for dragonflies and birds.

There are many now little-used names for groups of animals, e.g. a gaggle of geese on the ground, a skein of geese in flight, or a murder of crows. A flock of gnats is called a ghost. It is an apt name. A flock of gnats in the canyon are not bothersome. One can walk or run through one without noticing them, unless one of hundreds happens to fall into your mouth, but flocks of hundreds of gnats visually appear and disappear like ghosts depending on their back-lighting.

In “Four Seasons” on this date, Barnes describes finding a sunflower in bloom in City Creek. (id. Nov. 9th).

November 3, 2016

November 3rd

Helicopter Seeds

5:00 p.m. After a major storm on October 31st that involved wind gusts up to thirty-five miles per hour, today parts of the road are still covered in the lobe shaped seeds of Boxelder trees. The seeds are about three-sixteenths (4mm) in diameter, but are attached at the end of a half-inch “wing”. Overall, the seed and wing give the impression of a musical note. The seeds hang in symmetrical pairs on a catkin, a collection of about twenty seeds. Along the road in the first mile, there are many of Boxelders up to fifty feet in height that are covered in catkins. I walk up to one to pull a couple of seeds off, and each seed is surprisingly still strongly attached to its catkin, even though the tree is leafless. I can see why it took thirty-five mile per hour winds to dislodge the seeds that are on the road. I raise one above my head let it go. It starts to rotate quickly and like its cousin, the maple seed, it “helicopters” down to the ground. Testing several Boxelder seeds, they travel an average trajectory at about thirty degrees from vertical. As any middle or high school geometry student can tell you using a 30-60-90 degree right triangle, this means that a seed released from the top of a fifty foot tree might travel twenty-five feet horizontally from its parent tree. This is just enough to land outside the canopy of the mother tree.

During a wind gusts on October 27th, as I jogging past Boxelders near picnic site 6, a few of these “helicopters” would dislodge and float down will a light rain. One was freed from the highest branch by a first gust of wind, and as it floated to eye level, a second wind gust blew through. With that burst of wind, the helicoptering seeds stopped in mid-air and rose slightly, but as the gust diminished, it resumed its descent to the road.

Until relatively recently, the aerodynamics of these flying seeds was a mystery. Using the same principles of flight that govern birds and jetliners, the seeds should technically not float or “helicopter” slowly to the ground. The seeds should drop like a stone. Solving that mystery also explained other instances of creatures that should not fly and should not be able to hover, including several found in the canyon, i.e. – bees, dragonflies and hummingbirds.

In 1991, Lentink at Wageningen University of the Netherlands, Dickson and their colleagues determined that helicoptering maple seeds had a different mechanism of flight than that used by bird or man. As the seed helicopters, the leading edge of the seed’s wing generates a small, horizontal tubular vortex over the wing. This generates a low-pressure vacuum that lifts or sucks the seed upward. Unlike a bird, the wing has no familiar aerodynamic lifting shape. In normal flight like that of a bird or airplane, a smooth laminar flow over a wing’s special shape, similarly generates low-pressure above the wing, and the relatively higher pressure under the wing then lifts the wing and plane or bird into the sky. These horizontal vortices are called leading edge vortices or LEVs.

You may have seen analogous vortices when using a paddle in the water, when moving your arms while standing a pool, or when a plane lands through fog. Horizontal vortices form off the tips of paddles, your arms, or the tips of an airplane’s wing. In the case of the seed, a spinning vortex forms over the entire length of the wing’s flat surface.

In 1996, Ellington of the Vrije University in the Netherlands and his colleagues extended this concept to explain how many insects, like bees, moths and butterflies, can fly when aerodynamically, they should be unable to do so. They found the beating wings of moths generating the same leading edge vortices seen in helicoptering maple seeds. In 2000, Z. Jane Wang at New York University modelled flapping insects wing and noted that for some insects, two counter-rotating vortices are formed. One is a higher pressure vortex under the wing and it pushes up, and the second is a lower pressure vortex that “sucks” the insect up. In 2001, Lauder at the Harvard University built mechanical insect wings in order to better model the leading edge vortices. In 2004, Adrian Thomas at the Smithsonian Tropical Research Institute and colleagues studied dragonflies tethered inside wind tunnels, and they imaged the counter-rotating leading edge vortices (id. Fig. 11). In 2011, Liang and colleagues at Purdue University built mechanical wings with rigid veins similar to those seen in both Boxelder seeds and dragonfly wings, and they found that the ridge veins increased flight performance.

Wasps, bees and dragonflies have a different number of wings. Wasps only have two wings; dragonflies and bees have four. Bees have smaller fore-wings that lock into the larger back wings to form a single wing surface during normal flight. Only the dragonfly has two sets of independently moving wings, and only it moves the wings out-of-phase: while one wings goes up, the other flaps down. The dragonfly can rotate the angle of attack for each wing independently. In 2008, Z.J. Wang noted that the out-of-phase beating gives the dragonfly additional-enhanced lift. These results of Ellington, Lauder, Wang and Thomas give a clearer picture of how the dragonflies seen in the canyon hover and do their amazing acrobatic maneuvers (August 11th).

In 2005, Warrick at the University of Oregon and colleagues showed how hummingbirds also use leading edge vortices to feed while hovering in front of flowers.

In conclusion, the canyon currently hosts many examples of where nature has solved the problem of flight and hovering using leading edge vorticies instead of a bird’s flapping aerofoils or man’s propellers: Boxelder seeds, maple seeds, Variegated Meadowhawk dragonflies, red-rumped central bumble bees, Bald-faced hornets, Black-chinned hummingbirds, and several moths, butterflies and other flying insects. The first dragonflies, the massive Protodonata with 30 inch wingspans, appeared in the fossil record 325 million years ago. Flowering trees first began to dominate forests in the Cretaceous period beginning 145 million years ago, and they co-evolved with bees. Hummingbirds appeared 22 million years ago (McGuire et al. 2014).

Today in the canyon, even though the Boxelders where hammered by the strong winds, only a small fraction of their catkins were dislodged. Most Boxelders are still thick with seeds, and I can still look forward to more future showers of helicoptering seeds on windy days.

October 19, 2016

October 19th

Watercress Foraging

1:00 p.m. During a post-storm cold but sunny day, four insects are on the road: a Praying mantis, immature Eastern Boxelder bugs, a Variegated Meadowhawk dragonfly, and an unidentified bee. The bee was possibly a domesticated honey bee with equal spaced black-dirty-yellow bands on its abdomen. While all trees have turned color, about fifteen percent of the trees along the road are now completely leafless.

Below picnic site 6, watercress beds line the north side of the road where a water seep runs year round. Watercress is also found there on the south side of the road in beds in the stream itself. The beds look mangy, but not because it is Fall and cold. Their tops are still uneven and chopped. In June, an extended family from one of the Southeast Asian countries came to the canyon over three weeks and harvested watercress in great leaf bags. It was a great family affair involving several generations – grandparents, parents, aunts, uncles, and young, playful, smiling grandchildren. Some of the elders were in traditional dress, and the children wore heavy metal tee shirts. It was unclear whether they were gleaning out of economic necessity or as cultural practice as they all piled into a large luxury SUV at the end of their gathering. But they took too much; the watercress beds have never fully recovered; and this is a metaphor for non-sustainable consumption that undercuts our confidence in modern post-industrial lifestyles.

According to local experts, and I am not one, there are many edible wild plants in the canyon in addition to the fruit tree cultivars. Pine needles and wild mint (Mentha arvensis) from the upper canyon can be used to make tea. Wild onion (Allum acuminatum Hook) and wild carrot (Lomatium dissectum) can be found in the spring. Blue elder berry bushes can be found along the upper canyon trail (Sept. 8th). With much labor, the bitterness of Gambel’s oak acorns can be leeched out, and the flour turned into pancakes. Stinging nettles (Urtica dioica) and thistles can be boiled and then used as greens. Mountain dandelion (Agoseris glauca Raf.) greens can be added to salads. Some say even oak and maple leaves are edible. Barnes notes that the Ute indians ate these and also the root of arrowleaf balsamroot (Balsamorhiza sagittata) that grows profusely on the ridge between City Creek and the Avenues and on the west side of the ridge between City Creek and Ensign Peak (“Four Seasons”, Sept. 1st). The bulb of the state flower, the Sego Lily (Calochortus nuttalli) is edible, and the Sego can commonly be found on the high-slopes and ridges of either side of canyon during spring. But not being skilled in plant identification and since some edibles are easily confused with look-alike poisonous plants, I have not tried any of these.

With next spring’s growth, the watercress beds should become even thick mats again.

October 9, 2016

October 9th

Filed under: European Paper Wasp, mosquitoes, picnic site 11, Variegated Meadowhawks — canopus56 @ 7:08 pm

Wasp Shock

8:30 a.m. Along the road, taxpayers provide free plastic bags for visitors to pickup their dog’s droppings; however, the dispensers purchased by the City do not work well. The rolls of bags frequently bind up inside the housing. At picnic site 11, I pop the lid to the dispenser in order to free the roll. Today, it is empty except for two plastic bag rolls and a small beginnings of the fan shaped nest of the European Paper Wasp (Polistes dominula).

The afternoon of the day following the last storm (October 6th), I also walk up to dispenser, and as usual the plastic bag roll will not feed out of its slit. I open dispenser’s lid to free the roll, and its top half (10 in. x 12 in. by 4 in.) is filled with about 100 bright-yellow European Paper Wasps. As I jump back in alarm, the lid drops open, and all of the wasps spill out into a pile at the base of the dispenser. A few remain within the dispenser and they cling to the plastic rolls. I brace for an en masse stinging, but the European paper wasp is not particularly aggressive, and the colony has been stunned into docility by the intense overnight cold. They crawl around on the plastic rolls and on the ground while staring at me vacantly. The face of the European paper wasp is similar to their relatives, the Bald-Faced hornets, who have a nest a quarter-mile down canyon. For the European paper wasp, the lines in their face where exoskeleton plates meet are colored yellow and not white as in the Bald-Faced hornet.

I checked back an hour later. The colony, including all the wasps clumped on the ground, have flown off. They have decided that building a nest in a moving plastic roll was not a good idea.

Human make micro-habitats, and, if possible, a parcel’s original plants and animals readily adapt to those changes. The wasp using a plastic bag dispenser is an example, and the holding tank public toilet around the corner from the dispenser at picnic site 11 is another. Mosquitoes are not a significant nuisance in the summer canyon; numerous insect and bird predators, like Variegated Meadowhawk dragonflies, keep them in check. This morning, inside the toilet at picnic site 11, humans have created an ideal micro-habitat for mosquitoes, and the walls of the toilet are covered in about one-hundred “no-see-ums”. They have a ready source of water in which to breed; they are protected from the predators outside by the toilet’s walls, and heat from decaying matter in the holding tank provides a source of warmth.

But on this cold morning, these mosquitoes, like the paper wasps, can do little more than weakly flail about on the walls. None can warm themselves sufficient to fly, and thus, I am able to take care of my morning business unmolested.

Across from picnic site 11 is the gas pipeline check value. Here and along the road, several hundred bright-yellow roadside sunflowers could be found at the height of the summer. Now, only two live yellow blooms remain.

October 8, 2016

October 8th

Filed under: Dragonfly, Variegated Meadowhawks — canopus56 @ 4:14 pm

True Name of the Dragon

10:00 a.m. At various times, I referred to dragonflies, but those references were generic and were without a identification of a specific species. On July 29th, I described dragonflies flying in a B-25 bombing formation, and on August 11th, I noted a dragonfly feeding frenzy. On August 22nd, I observed cliff swallows feeding on dragonflies. Dragonflies move so fast that a certain identification is impossible and they rarely cooperate by conveniently resting on a leaf or stalk.

This morning, insects are still recovering after the storm of October 5th, and a few dragonflies, cabbage white butterflies, and moths can still be found. However, because the overnight temperatures have been in the 30s, they are all sluggish. In the cool morning air at mile 1.2 and 1.6, I find two separate dragonflies sunning themselves on the road. They are so punch-drunk from the cold that they do not fly off when approached.

They have the clear perpendicular wings that are the mark a dragonfly, and their abdomens are segmented in brown and pale yellow stripes. Dragonfly eyes are unique and if they have 10,000 to 30,000 lenses in their compound eyes. This allows them to perform the precise acrobatic maneuvers needed to catch small insects. In contrast the house fly has 3,000 to 5,000 eye lenses in its compound eyes.

After taking a photograph and doing some research, field guides instruct that these dragonflies are immature Variegated Meadowhawks (Sympetrum corruptum). The meadowhawks are a member of the skimmer dragonfly family (Libellulidae), and they differ from other families in that they have a distinctive lobe at the margin of each eye. I unable to distinguish this feature between photographs of various types of dragonflies.

The term meadow “hawk” is ironic. Although these hawks are a predominate predator of small insect world, the meadowhawks themselves are prey for the cliff swallow, the scrub jay, the Mountain chickadee, and the Northern flicker.

In the Norse and Germanic legends, knowing the true secret name of a creature gives one special powers, e.g. – the release of the miller’s daughter from the imp’s curse when she speaks his name, “Rumpelstiltskin”. When I return to the canyon tomorrow, I will in the style of a currently popular childrens’ book character, raise my wand and speak the true name of the meadowhawk, “Libellulidae sympetrum corruptum.”  I anticipate that the meadowhawks will continue in their aerial contortions and will remain oblivious to my bidding.


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