May 26, 2013
BARN SWALLOWS BUILDING A NEST
Barn Swallows overwinter from southern Mexico south throughout Central and South America. They showed up here several weeks ago and this week a couple began flitting past my computering window many times a day, and buzzing my head when I stepped outside the door. You can see one flying past the door with wings blurred, upper parts a solid cobalt-blue, tail deeply forked, and with a rusty throat and pale breast at https://www.backyardnature.net/n/13/130526ns.jpg.
The swallows flew in and out from under the shed's eaves so it was easy to guess that they were building a nest there. I peeped up from below and saw what's shown at https://www.backyardnature.net/n/13/130526nt.jpg.
That nest is unfinished, the straw and plant roots forming the nest's interior not yet completely covered over with daubs of mud. My neighbor irrigates his big garden so during this time of extreme drought in our area mud was gathered where water pooled between the garden's planted ridges.
Roof eaves just as good as this one outside my door are available all through the valley, on vacant houses, on barns and sheds seldom visited by people, and even on my laundry shed's other side. However, this pair of swallows chose to build exactly where I enter and leave the cabin several times each day.
It was the same back during my hermit years in the forest near Natchez, Mississippi; animals who could have nested in so many places chose instead the very edge of my camp, and sometimes even beneath the roof where I made my campfires. I'm convinced that species such as the Barn Swallow often are attracted to spots with people moving about. Is it more because predators are less likely to come near my door, or because the birds are fascinated by human behavior? How much of their choice-making is like human thinking, and how much is mechanical?
Whatever the reasons, I'll be watching these swallows, and maybe have more stories and pictures later on.
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PLANARIAN IN A JAR
During the cold months when not much was flowering or fruiting I explored life in the little Dry Frio River's shallow waters behind the cabin, focusing especially on algae and protozoa. I placed jars of Dry Frio water on my window sills and through the months it's been fascinating watching how these little biosystems evolve, some species dying out, others proliferating, and each jar seems to have developed differently. One jar's water is murky green because of an alga population explosion, but water in the jar next is clear with a modest little sprig of some kind of flowering plant, and a third jar is in-between, but home to thousands of darting-about microbes who show up as specks when the morning sun shines through it.
This week in one jar, and only one, the walls became peppered with tiny freshwater snails and minute, brownish, worms that moved across the jar's walls. I fished one of the worms out, coaxed it onto a microscope slide, and you can see it at https://www.backyardnature.net/n/13/130526pl.jpg.
That picture is not taken through a microscope because he was too large -- about ¼ inch (7mm) when extended. The photograph shows him drawn up to maybe a quarter of that length. Still, the field marks telling us what this animal is are easy to see: He's a flat worm whose head bears two conspicuous eyespots, or ocelli, giving the impression that they're "crossed," and the head is "eared" like an arrow with a rounded point.
Most everyone who has taken a biology class can instantly recognize that this is a planarian, for biology classes the world over study planaria because they're so easy to keep alive and possess an interesting nervous system. A planarian split lengthwise or crosswise will regenerate into two separate individuals. In fact, very small cut-out pieces of certain planaria as little as 1/279th of the organism can regenerate back into a complete organism over the course of a few weeks. You may have seen pictures of a planarian with its head cut in half down its center, resulting in a planarian with two complete heads.
Many kinds of planaria exist, some terrestrial, many marine, some freshwater like ours. They move by beating cilia on their undersurfaces, enabling them to glide along on a film of mucus. Some species can move by undulating their bodies. I read that freshwater planaria eat protozoa. Ours appeared to be grazing the jar's inner walls along with the snails. However, planaria don't have the snail's raspy tongues with which to scrape algae off the glass. Instead, planaria have a single opening or mouth at the end of a muscular tube, the pharynx, which is extended when feeding. It's hard to see how such a snaky pharynx might be used on a class wall. Maybe ours were just out exploring among the snails. Other individual planaria were down in the detritus at the jar's bottom, which was rich in one-celled protozoa, and a flexible pharynx might easily come in handy there.
During my hermit days in Mississippi I ran into an invasive planarian species about half a foot long. You might enjoy reading about that one, seeing it, and comparing it to our little jar-wall traveler at https://www.backyardnature.net/n/a/planaria.htm.
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ROBBER FLY
While I photographed a wildflower an unusual fly-like critter a little less than an inch long (±2cm) landed on a stem next to me, as seen at https://www.backyardnature.net/n/13/130526rf.jpg.
This is a robber fly, genus EFFERIA, a male one. He's clearly a male because the black item stuck at the abdomen's tip is the genitalia. Females lack such an appendage, their abdomens ending with slender points.
Efferia is a big genus -- 22 species are listed just for Arizona -- and they're hard to distinguish. However, they're all known as robber flies. Robber flies eat many kinds of flying insects, from mosquitoes and June bugs to honeybees, whom they catch in flight. Upon capturing prey the flies land, inject their victims with digestive enzymes that liquefy the prey's innards, and finally suck out the victim's juices.
You might remember the robber fly we saw in the Yucatan, a male who landed on a leaf behind my hut, warming his body and oversized genetalia in the rising sun. You can compare our present one with the Yucatan one at https://www.backyardnature.net/yucatan/robber-f.htm.
Robber flies are members of the fly family Asilidae, of which about 7,000 species have been identified worldwide.
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WATER-WILLOW FLOWERING
The US Drought Monitor Page at http://droughtmonitor.unl.edu continues to say that here we are experiencing a D4-level "exceptional" drought, which they define as more extreme than the D3 "extreme" one. The little Dry Frio River behind the cabin has become a chain of isolated pools separated by gravel ridges. Still, here and there pools are large and frog-inhabited enough that visiting them you can almost forget the drought. A pretty picture showing one such pool is at https://www.backyardnature.net/n/13/130526ju.jpg.
Trees along the banks are mostly American Sycamores. However, here we're interested in the knee-high, leafy switches emerging from the water from bank to bank bearing willow-like leaves and white flowers, as shown at https://www.backyardnature.net/n/13/130526jv.jpg.
Mud on some of the plants' stems indicates how fast the water level has been dropping. The ¾-inch broad (2cm) flowers are worth bending over to look at, for they're almost like miniature orchid flowers, as shown at https://www.backyardnature.net/n/13/130526jw.jpg.
This herbaceous, aquatic perennial is one known by everyone in the eastern US and adjacent Canada who visits wetlands and pays attention: It's the American Water-willow, JUSTICIA AMERICANA, a member of the Acanthus Family, the Acanthaceae.
In Mexico we experienced the Acanthus Family as a big, commonly encountered one, but here in the Temperate Zone not many species in the family can survive our winter temperatures. So that's something special about water-willows: They're the most cold-tolerant members of their mostly tropical Acanthus Family. In southern Canada, where the American Water-willow is the only native representative of the Acanthus Family, it's so rare that it's officially regarded as threatened, and a program is in place to reintroduce the species.
Good field marks for the Acanthus Family, nicely displayed by our water-willows, include the fact that the flowers are bilaterally symmetrical -- they're "zygomorphic" like most mint and orchid flowers -- not radially. In other words, there's only one plane across which you can cut the blossom resulting in mirror images on both sides of the plane. Also, flowers bear either two or four stamens, not the more typical five or multiples thereof. Leaflike bracts beneath the individual flowers, and fruits shaped a bit like upside-down violins confirm the family.
In our flower picture you can see that our water-willow blossom has two stamens, each consisting of a white, slender filament curved at the top where it bears two dark brown, pollen-producing anthers facing away from one another. In our photo the nearest anther cell has been eaten off. The slender, white style emerges between the two stamens and rises above them. The style it tipped with a tiny, Y-shaped, white stigma. The style is the "neck" between the ovary at the flower's bottom, and the stigma at the top. Water-willow flowers are mostly bee pollinated.
In Uvalde County we have a second member of the genus Justicia, the purple-flowered Hairy Tubetongue, Justicia pilosella, which we met in the April 7th Newsletter. You might enjoy comparing the Water-willow's flower with that of the tubetongue's at https://www.backyardnature.net/n/h/tubetong.htm.
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GOLDENMANE
Biking across the Dry Frio's valley floor, thanks to our long-term drought, most of the grassland still is dun colored with few wildflowers. Pictures from past years at this season show a profoundly green and floriferous grassland between the hills. Still, around buildings where a little rain has run off roofs you get green patches, as well as alongside streams, or what usually are streams. One spectacular wildflower showing up as soon as you approach the immediate gravelly or cobblestone floodplain of certain streams is the one shown at https://www.backyardnature.net/n/13/130526cc.jpg.
A close-up of one of those pretty flowering heads is at https://www.backyardnature.net/n/13/130526cd.jpg.
This 15-inch tall (40cm) wildflower is obviously a member of the huge Daisy or Composite Family, so the yellow, purple-based, petal-like things radiating from the flower head's dark center are ray flowers, while the dark "eye" is composed of numerous tightly crammed together, dark purple disc flowers.
Very often but not always when you see a daisy-type wildflower on which the yellow ray flowers are lobed at their tips as on this blossom, you have a member of the genus Coreopsis, and that's the case here. This is COREOPSIS BASALIS, often known as Goldenmane. Goldenmane is endemic to Texas and a bit of Oklahoma and Louisiana. It's so pretty that it's planted in gardens elsewhere, and has escaped into the wild in much of the US Southeast and southern California.
In our area there's another very similar and closely related coreopsis, Coreopsis tinctoria, sometimes called Goldenwave or Plains Coreopsis, and that species is much more widespread and more extensively escaped into the wild than our Goldenwave. The easiest way to distinguish the two species is that our Goldenmane's ray flowers are mostly deeply four-lobed at their outer ends, while the Goldenwave's are typically three-lobed -- though sometimes the middle lobe will be slightly cleft.
In fact, I thought I had a Goldenwave before I "did the botany," because back in Mississippi and Kentucky we had the more common Goldenwave. However, Coreopsis is a big genus with numerous endemics sprinkled here and there, so I knew I'd be "do the botany" before saying anything about this particular plant.
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TEXAS THISTLES
Last week we looked at the Nodding Thistle, an invasive from the Old World much despised by ranchers and farmers. There's another thistle common here in the grassy area around the cabin and along roads, and I've been looking forward to identifying it. For, most thistles you run into are weedy and people only want to get rid of them. However, in this area we have so many rare endemics that I thought the one around the cabin might be one of those native thistles of such limited distribution and finely tuned adaptations to local conditions that it can only be classified as a wildflower. You can see a knee-high one next to my laundry shed at https://www.backyardnature.net/n/13/130526cm.jpg.
A close-up of a head with the bottom green, spiny part -- the involucre -- a bit smaller and more spherical that the involucres of most thistle species, and with unusually short, fine spines sticking out at right angles is at https://www.backyardnature.net/n/13/130526cn.jpg.
That picture also shows a feature that's fairly uncommon among the thistles, and that is that the individual bracts of the involucre, the phyllaries, each bear a conspicuous silvery strip down their middles -- a "prominent glutinous ridge," as the Flora of North America calls it. As soon as I saw this, already I had a feeling that this species was something special, not a rank invasive weed.
Some of our most aggressive weed thistles have their leaf margins continuing down the stem as narrow "wings." However, this thistle's leaf bases bore spiny ears that wrapped around the hairy stems, as shown at https://www.backyardnature.net/n/13/130526co.jpg.
Also in that picture, note that leaf undersurfaces are white with wooly hairs.
So, when I "did the botany," this thistle species did indeed reveal itself as a wildflower and not a weed. It goes by such names as the Texas, Southern and Purple Thistle. It's CIRSIUM TEXANUM, native to northern Mexico's Chihuahuan Desert, extending into the US from New Mexico across the plains of Texas and southern Oklahoma to southwestern Arkansas and southwestern Louisiana. Its original habitat was deserty savannas but now it also finds what it needs along roadsides, in pastures and fields.
This is a fine species, one from which pollinators such as bees take plenty of nectar. Larvae of Painted-lady Butterflies feed on the leaves and finches of different kinds crave the thistle seed.
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TEXAS THISTLE'S FLYPAPER STRATEGY
Above we mentioned the "prominent glutinous ridge" running down the back of each scale-like bract, or phyllary, covering the green, cuplike involucres constituting the greenish, spiny bottom part of each Texas Thistle flower head.
Glutinous means sticky, but I didn't realize how sticky the phyllary ridges were until I got close enough to see what appeared to be reddish debris accumulated among the spines at the bottom of each flower head. You can see a close-up of that debris field at https://www.backyardnature.net/n/13/130526cq.jpg.
Those are ants -- invasive, misery-causing, ground-nesting-bird-killing fire ants, and none of them appeared to be moving. I thought that maybe they were eating the scales' glutinous stuff, so I snipped off a thistle head and put it below the objectives of our dissecting scope. What I saw was appalling, even knowing that these were awful fire ants. It was like a battlefield with corpses frozen in grotesque, inexplicable poses, a mad frenzy of legs, antennae and thistle spines, but completely unmoving, everything dead. You can see a random view of the carnage, with fire ant legs and body parts lethally adhering to the phyllaries' glutinous ridges at https://www.backyardnature.net/n/13/130526cr.jpg.
So here's a defense against nectar robbers who approach the thistle's nectar-rich flowering heads from below. Spines further keep grazing herbivores from nibbling the heads from above. Probably chemicals in the leaves prevent certain insects from eating them, too.
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HAIRY WOOLLYGRASS
Along an isolated gravel road where the soil was so thin and hard-baked that only ankle-high vegetation could get a foothold, there was a house-size community of closely growing together short grasses. They caught my eye because their flower clusters, or inflorescences, were oversized for such a short grass, and this early in the season the inflorescences were already maturing to a pale dun color. The relatively large, straw-colored flowering heads atop green grass looked a little funny, like a young man with gray hair. You can see the effect at https://www.backyardnature.net/n/13/130526wg.jpg.
The inch-tall (3cm) flowering heads, which were spikelike panicles, also were a little odd looking, blousy at the top but compact below, as shown at https://www.backyardnature.net/n/13/130526wh.jpg.
If you look at that picture closely you see that the panicle expands at the top because the topmost spikelets have matured but those at the bottom are still green. Florets in spikelets at the top are enlarging and developing long hairs in preparation for breaking away from the spikelet.
This quirky little grass is known mostly by the redundant name of Hairy Woollygrass. It's ERIONEURON PILOSUM, found in the southwestern quarter of the US and in arid zones throughout most of Mexico, plus there's an isolated, or "disjunct," population in Argentina.
In Hairy Woollygrass, instead of the florets opening up to release their caryopsis-type fruits, or grains, the florets remain intact but come loose as a unit from the stem bearing the florets -- they disarticulate from the rachilla -- and then wind catches in the florets' fuzz and helps them disseminate. You can see some loose florets with their woolly parachute-hairs at https://www.backyardnature.net/n/13/130526wi.jpg.
Seed-eating birds such as our abundant Lark Sparrows feed on these grains but I think the main ecological service this tufted, perennial grass provides is to flourish in soil that's too thin and dry to support other species. If our current severe drought and hotter-than-average summer continues, Hairy Woollygrass may prove to be one of the most important organisms holding our dusty soil in place.
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COLLECTING MUSTARD SEEDS
You might remember how during the cold months often I rhapsodized on the glories of meals in which hot cornbread and mustard/turnip greens were the main or only features. Weeks ago my mustard greens turned bitter and bolted, producing big, pretty heads of yellow flowers that hosts of pollinators sought every day. Once the flowers were gone I pulled most of the plants but saved several at the end of one bed for seed. Nowadays that part of the bed looks scroungy enough, as shown at https://www.backyardnature.net/n/13/130526mg.jpg.
Most of the diffuse clutter in that picture consists of dried fruit capsules. A close-up of some bulging with tiny seeds is shown at https://www.backyardnature.net/n/13/130526mh.jpg.
The capsules are easy to dislodge from the plant stems by roughly raking them between the fingers. The capsules' sides easily break away to release the seeds when you roll the capsules between your hands. You can see some split-open capsules and seeds that have collected in a plastic tray held beneath the capsules as they were being maltreated at https://www.backyardnature.net/n/13/130526mi.jpg.
Mustard greens seed are cheap enough, but somehow I like the idea of collecting my own, not only for the tradition involved but also to keep in practice for when the infrastructure collapses. Someday I just might be thankful that in a tightly sealed jar in a cabinet someplace I have enough mustard seeds stored up for all the greens I can eat during the cold months.
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FEATURED ESSAYS FROM THE PAST:
"Four Points of Being a Maya Man," from the August 8, 2010 Newsletter, at https://www.backyardnature.net/n/p/100808.htm.
"Glutinous & Rugose," from the January 21, 2008 Newsletter, at https://www.backyardnature.net/n/p/080121.htm.
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Best wishes to all Newsletter readers,
Jim
Visit Jim's backyard nature site at https://www.backyardnature.net
