March 17, 2013
MARTINS HAVE LANDED
Last Sunday, March 10th, a certain familiar, bubbly chortle cascaded from the sky, and sure enough it was a pair of Purple Martins freshly arrived from Brazil or thereabouts for their summer of nesting. You can see the pair on the bird box just a few feet from where I was sitting at https://www.backyardnature.net/n/13/130317pm.jpg.
The female with her gray underparts perches at the left while the blackish blue male attends at the right. Normally male "scouts" who search for nesting sites arrive a few days before the females, so probably the male was here earlier. You can see the status of arrival of male scouts across North America, and report your own scouts' arrivals, on the Purple Martin.org Scout Report Page at http://purplemartin.org/scoutreport/.
It's the female who decides where to nest, and which male she wants to pair with for the season. She often returns to where she nested previously. Upon her arrival, her first job is to review the available males competing for her and other females. Once a pair is bonded, both sexes share in nest building and maintenance, in defending the nest, and both feed and care for the offspring. Purple Martins often nest in colonies, but members of the breeding colony are not related.
Martins are monogamous, but both sexes are highly promiscuous. Females may have multiple mates while maintaining a single nest. Studies show that the less impressive the male is in a bonded pair, the more likely the female is to mate with other more dynamic males during the mating season. From an evolutionary perspective this is an elegant strategy because it provides more dynamic birds more chances to pass along their genes, while not wasting the willingness of less desirable males to defend a nest and care for nestlings.
In August of 2011 when I was writing from the Caribbean beach of eastern Yucatan, hundreds of martins migrated down the coast every day, migrating back to South America. You can see a picture from then showing them shoulder-to-shoulder on the resort's antenna guy-wires and tower at https://www.backyardnature.net/n/11/110807pr.jpg.
Our visiting martin couple here along the Dry Frio didn't stay long and didn't return on subsequent days, so probably the female didn't like the nest and/or the male she was with. One problem with the nest may have been that House Sparrows already had occupied several compartments in the bird box. You can read about House Sparrows and Starlings being "super competitors" for Purple Martins at http://purplemartin.org/forumarchives/archive/Supercompet.htm.
Another interesting essay on "vindictive sparrows" making it hard for martins to nest is at http://purplemartin.org/forumarchives/archive/HSrevenge.htm.
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MENODORA, LOVER OF SUN & WIND
During all my walk I'd been scanning the woods edge and the understory for spring wildflowers, but there were none. However, returning home, in mostly bare, sun-scorched, windblown, drought-cracked, deer-trampled clay at the gravel road's edge finally I did spot something new, a small, sprawling, silvery-leafed, sand-encrusted plant with bright yellow blossoms about ¾-inch across (20mm), as shown at https://www.backyardnature.net/n/13/130317mn.jpg.
A close-up of a flower with its spherical stigma and two shorter stamens well exserted from the corolla tube, beside the plant's deeply incised leaves is shown at https://www.backyardnature.net/n/13/130317mo.jpg.
This blossom was unusual because of its prominent stigma and only two stamens. The more typical arrangement for such a flower would be to have an inconspicuous stigma down in the corolla tube, and five stamens. For a better look at the quirky bloom I tugged at the corolla and the whole thing came loose as if it were just lying in its calyx. In fact, now I noticed that already that morning several flowers had opened, wilted, and fallen to the ground. Breaking the corolla in my hand lengthwise along one side, I opened it up and saw how the stamens were attached to the corolla tube, as shown at https://www.backyardnature.net/n/13/130317mp.jpg.
I couldn't recall having ever seen such a large, yellow, radially symmetrical blossom with only two stamens attached to the tube wall. What family would such a flower belong to? The deeply incised leaves arose in pairs at each stem node, as if we had a member of the Mint or Verbena Families. Flower ovaries in those families are deeply to somewhat 4-lobed, but these flowers' ovaries weren't. However, often parts of such 4-lobed ovaries abort and the developing fruit turns out looking more or less like what I was seeing. I decided that the scrappy little plant probably belonged to the Verbena Family, largely because certain creeping, dry-place-loving Verbenas bear leaves more or less like it. However, the blossom certainly didn't look like a Verbena flower! Really, this plant was a mystery, and that was great.
After wasting a couple of hours imagening the little plant to be a member of the Verbena Family finally I figured out that it was something else entirely, and much more interesting. The plant in our photo is MENODORA HETEROPHYLLA, sometimes known as the Low Menodora, or Redbud. To Easterners used to Redbud trees, the name Redbud may sound out of place, but when you see a corolla of this plant about to open up you understand immediately where the name came from. You can see such a flower bud at https://www.backyardnature.net/n/13/130317mq.jpg.
A view of the underside of a freshly open flower shows what happens to the buds' crimson surface area at https://www.backyardnature.net/n/13/130317mr.jpg.
The Low Menodora is a member of the Olive Family, the Oleaceae. Other members of the Olive Family North Americans might be familiar with include Privet shrub, Jasmine, Lilacs and ash trees. And they all look very different from our little ground-hugging, yellow-flowered plant.
The Low Menodora is described as living on clay, gravel and sandy loam of caliche outcrops and rocky hills, as well as in mesquite pastures in central and southern Texas, south to central Mexico... and, amazingly, in Botswana, southern Africa. The plant's occurrence in two such widely separated distribution areas as Texas and Botswana is highly unusual, and as of yet is unexplained. The two populations became separated a long time ago, however, because now they constitute two distinct varieties. In other words, the populations separated long enough ago for them to have evolved different features, but not long enough ago to have formed two completely different, genetically isolated species.
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PERIWINKLE FLOWERING
Upon my arrival here last August my first task was to clear periwinkle vines from flower beds next to the cabin. The periwinkles formed a pretty, green carpet on the ground but the vines climbed the cabin's walls, wedging themselves beneath loose-fitting boards and seeming to pry certain boards apart, and even snaking between boards into the porch, where they sprawled across the floor and climbed up screens. Though I cleaned every visible sprig from the beds, periwinkle stems can root and sprout at their nodes, so before long every stem segment left behind beneath a rock or the flower beds' timbers produced a robust new plant issuing welcome greenery all through the winter.
This week some of the sprouts flowered. Knowing the cabin owner would want all the periwinkle uprooted again, I broke off a piece with its purple blossom and held it against the blue sky, creating the image shown at https://www.backyardnature.net/n/13/130317vi.jpg.
In North America we have two common periwinkle species, Vinca minor and Vinca major. This is VINCA MAJOR, sometimes distinguished from the other species by the names Bigleaf Periwinkle, Greater Periwinkle, and the like. If the two periwinkle species are seen side-by-side it's easy to distinguish them, for leaves of Vinca minor are relatively narrower and only 0.8 to 1.8 inches long (2 to 4.5 cm), while leaves of our Vinca major are heart-shaped to triangular, and 1.5 to 2.5 inches long (4 to 6 cm). However, in the field you see lots of variation and overlapping of features, so it's not always easy to distinguish them. A little trick proving that you have our Bigleaf Periwinkle, Vinca major, is shown at https://www.backyardnature.net/n/13/130317vk.jpg.
Those are a Bigleaf Periwinkle flower's slender sepals -- the green, cuplike calyx divisions below the corolla -- and their margins are hairy. Sepal margins of Vinca minor are hairless.
Both common periwinkle species are invasive introductions from Eurasia. They're members of the big Dogbane Family, the Apocynaceae, a family famous for its species containing powerful chemicals with medicinal and toxic properties. Therefore it's no surprise that every part of the periwinkle contains low levels of alkaloids that, if eaten in large enough quantities, can be harmful to dogs, cats, horses and humans. Symptoms include abdominal cramps, vomiting, diarrhea, a drop in blood pressure, lethargy and/or tremors or seizures. Larger doses induce coma or even death.
But, this is a handsome species, and I'm grateful to it for its purple blossoms here so early in spring. I appreciate the greenness it has provided all winter and I even admire its lusty persistence. I'll pull it all out, though, because it seems intent on tearing the old cabin's walls apart, and in claiming all the flower-garden space for itself. Besides, it's clear that it'll reassert its claim to this land as soon as I leave. I suspect that someday long after the last human has disappeared from this community, the entire neighborhood may become carpeted in dark green periwinkle vine only here and there with a sprig of Big Bluestem rising above the carpet.
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A FLOWERING SEDGE
Hiking beside the little Dry Frio River, across a low cobblestone terrace sparsely inhabited with flash-flood-shattered Sycamores, I was about to give up on finding anything new flowering when I came upon a hat-size clump of wiry looking grass, or something that looked like grass, bearing flowers at the tips of some its stems. The unspectacular tuft is shown at https://www.backyardnature.net/n/13/130317cx.jpg.
A quick look at the flowers let me know that we weren't dealing with a grass, but rather a sedge in the Sedge Family, the Cyperaceae. You can see one of its very un-grasslike flower clusters at https://www.backyardnature.net/n/13/130317cy.jpg.
In that picture the vertical spike at the far left consists of only male flowers while the smaller, thicker spike sprouting from the male spike's base bears only female flowers. The long, slender thing parallel with the bottom of the picture is a bract arising at the spikes' base. It's included in the picture because often the length of the bract relative to the lengths of the spikes is important in identifying sedges to species level.
And sedge identification can be hard, mainly because there are so many species -- some 2000 species of the sedge genus Carex. The online Flora of North America treats 480 species. Knowing I had a real challenge on hand to identify this cobblestone-field sedge I got close-ups of the flowers, shown at https://www.backyardnature.net/n/13/130317cz.jpg.
In sedges, typically male and female spikes mature at different times, thus avoiding self-pollination. The male spike in the previous photo either is shown before or after its anthers released pollen. A spike with its anthers still attached and shedding pollen is shown at https://www.backyardnature.net/n/13/130317cw.jpg.
So, important field marks for this species include the before-mentioned fact that male flowers occur in the "terminal spike" while female ones occupy spikes arising below the male spike. About half of North America's 480 sedge species, instead of having oval female parts (perigynia) like ours, are shaped like convex lenses in magnifying glasses, so that disposes of quite a few potential species right there. Of those with oval perigynia, many produce hairy perigynia but others, like ours, are hairless. Only a small group of sedges with oval, hairless perigynia have perigynium necks as strongly bent to one side as ours. Finally, notice that the sides of the sharp-pointed scales subtending each perigynium are brownish.
Despite all these details, just by using the photos when I got them onto my laptop, I was unable to identify the sedge to species. It keyed out to Carex meadii, but that species doesn't form such thick tufts, and I'm told by someone familiar with that species that ours isn't it. Simply by matching pictures on the Internet and by looking at other people's lists of sedge species found in this area, my best bet is that we have the Cedar Sedge, CAREX PLANOSTACHYS, a species described as living in dry to mesic forests and scrub, on calcareous soils in Arkansas, Oklahoma and Texas, south through eastern Mexico into Guatemala.
So, this is a nice find, a surprising one, and a welcome one in a time and place where any spring-flowering plant would have been welcome.
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ORION
In the evening as soon as stars are shining brightly, if you step outside, you're away from light pollution and you're in the Northern Hemisphere you can't miss the constellation Orion. Along with the Big Dipper, or Ursa Major, Orion is one of the best known and easiest to identify of all constellations. It's worth taking a look at Orion nowadays because not only is it easy to see right in the center of the night sky a little after dusk, but also there are interesting things to know about. By placing my mid-range, off-the-Walmart-shelf camera on a tripod, using the lowest F-stop of 2.8, and keeping the shutter open for 15 seconds, this week I took the picture of Orion shown at https://www.backyardnature.net/n/13/130317or.jpg.
Orion is easy to recognize not only because of its large size and prominent position in the sky at this time of year but also because of the two sets of easy-to-see stars lined up three in a row. Orion is "The Hunter," so the three stars forming a horizontal line in the picture's center constitute Orion's belt, while the other three, smaller and closer-together below and to the left of the belt, represent the sword hanging from the belt.
The bright star at the picture's top, center -- that's the famous Betelgeuse -- represents one of Orion's shoulders, while the other bright star at 4 o'clock from Betelgeuse, known as Bellatrix, makes up the other shoulder. Orion's head is formed by the cluster of stars near the picture's top, right corner. Knowing where the head, shoulders, belt and sword are, you can figure out the two bright stars representing Orion's feet at the picture's bottom. Those stars are Saiph at the far left, and Rigel at bottom center.
Of the stars mentioned above, Rigel is famed as the sixth-brightest star in all the night sky. It's a "blue supergiant." Betelgeuse is a red supergiant.
In our picture you might notice that the middle star in Orion's dangling sword is fuzzy-looking. That's because it's not a star but rather the Orion Nebula, also known as M42, an enormous cloud of gas and dust, one of many in our Milky Way galaxy. It lies roughly 1,300 light-years from Earth. In this nebula it is thought that thousands of new stars are being born, formed of coalescing gas and dust.
There's plenty more to know about the stars, nebulae and deep-space objects occurring within the star field known as Orion. Wikipedia's Orion Page is at http://en.wikipedia.org/wiki/Orion_(constellation).
By the way, from the shoulder represented by Betelgeuse, at the picture's top, center, Orion raises a club-wielding arm above his head, presumably on account of Taurus the Bull, the constellation to Orion's right in the current night sky. The club is formed of weaker stars however, and our picture doesn't show them. Similarly, from the shoulder made by Bellatrix, Orion's arm extends westward bearing a curved shield, but these shield and arm stars also are too faint to feature in our picture. On a clear night, though, you can make out the club and shield, and the arms holding them.
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FEATURED ESSAYS FROM THE PAST:
"Howdying the Universal Creative Impulse," from the December 21, 2010 Newsletter, at https://www.backyardnature.net/n/p/101219.htm.
"If There Were An Einstein Tadpole," from the August 18, 2002 Newsletter, at https://www.backyardnature.net/n/p/020818.htm.
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Best wishes to all Newsletter readers,
Jim
Visit Jim's backyard nature site at https://www.backyardnature.net
