February 7, 2016

THIRSTY KISKADEE
As the dry season starts to bear down the birdbath in front of the hut receives more and more daily visitors, mostly Melodious Blackbirds and Clay-colored Robins, but one Great Kiskadee Flycatcher regularly comes, shown at https://www.backyardnature.net/n/16/160207kk.jpg.

I don't know what's going on with this particular bird. Nowadays most of his kind go about calling the usual full-blown KISS-ka-DEE! calls and other raucous shrieks and general outbursts, but this one, sometimes hour after hour, for days, has been flying around calling Wahhh!, Wahhh!, and sometimes I wish he'd stop.

The birdbath is placed so I can see it from where I work at the computer in the hut, so probably as the season develops I'll have more shots like this.

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METAMORPHOSING CACTUS BUGS
Last November Cactus Bugs turned up mating on the edible, seven-ft-tall (2m) Nopal Cactus in front of the hut, and in January we documented subsequent crowded clusters of colorful Cactus Bug nymphs on the same cactus. Those goings-on are described and illustrated on our Cactus Bug page at https://www.backyardnature.net/mexnat/cact-bug.htm.

This week most of the nymphs metamorphosed into adults. You can see a whitish one with pink highlights almost finished emerging from its blackish husk at https://www.backyardnature.net/n/16/160207cb.jpg.

Another shot of one whose emergence is less advanced than the one's above reveals how during emergence the head is bent tightly against the abdomen's bottom, at https://www.backyardnature.net/n/16/160207cc.jpg.

The pictures are shown out of sequence because that last one can be hard to interpret if you don't know what you're looking for. When I first saw an emerging nymph in this stage I thought it was headless, and saw the head only once the picture was on the laptop screen.

Freshly minted adults remain whitish for several hours but by the next day they display the adults' typical colors, shown at https://www.backyardnature.net/n/16/160207cd.jpg.

In that photo recently emerged adults stand next to nymphs that are far from reaching the instar stage at which they also will become adults. We noted earlier that clusters on the hut cactus contained nymphs of various age groups.

Compared to now last week maybe three times the number of nymphs could be found on the cactus, in two or three groups, but something happened to most of them. I noticed this after a particularly chilly night with intermittent sprinkles, but don't know whether there was a connection.

Sometimes when I put my face up close to the cluster one or two larger nymphs raise their rear ends and squirt out drops of fluid. Maybe they do this all the time, or maybe they're doing it just for my benefit.

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CHAMISSOA VINE
Near the hut a wall of secondary forest rises beside the trail, its young trees tangled with morning glories and other vines. One vine is different from the others, so stiff and tough it's almost a clambering shrub, and its flowers are tiny, held in large, open clusters that cascade from the wall. You can see the whole thing silhouetted against the blue sky at https://www.backyardnature.net/n/16/160207ch.jpg.

Up close, the vine-bush's leaves are soft and plain looking, with long, slender petioles, and the tiny flowers are pale and chaffy, in small clusters widely dispersed along the inflorescence's stem, or rachis, as shown at https://www.backyardnature.net/n/16/160207ci.jpg.

Even at that distance, those familiar with common weeds and wildflowers will recognize from the clusters of chaffy, pale flowers that this is a member of the Amaranth Family, the Amaranthaceae. Sometimes in this family the flowers are so tiny, closely packed and generally closed up that it's hard to find an open blossom, but on this plant with its widely spaced clusters open flowers are easy to find, and they're unusual and worth studying, as shown at https://www.backyardnature.net/n/16/160207cj.jpg.

Here are some notable features about the blossoms.

This vine is so distinctive that it was easy to identify just by doing image searches on the Amaranth Family species listed for the Yucatan. It's CHAMISSOA ALTISSIMA, commonly occurring in secondary forests from southern Mexico and the Caribbean south to Peru and Brazil. Sometimes the English name False Chaff Flower is applied to it, but that sounds like an editor's name that real people don't use, and I don't like names that label plants "False," so I prefer thinking of it as Chamissoa Vine, probably best pronounced KAM-eh-SO-ah.

Small, seed-eating birds must feed on Chamissoa Vine's seeds. The vine's preference for secondary forests makes it part of "Nature's First Aid Crew," helping forests reestablish themselves after being destroyed or damaged.

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SMALL MATWEED
Last November at the rainy season's end I was surprised to find Mudplantain in a pool of water on an isolated trail. This week I returned to that spot interested in seeing what remained of that population. Nothing that I could find remained, just hard, thin, dry dirt atop limestone, some dried-up and dead herbaceous plants, and few green plants on the verge of drying up.

However, there was one small, ground-hugging plant doing better than the rest, drawing attention to itself with its pale, light-gathering flowering heads, as shown at https://www.backyardnature.net/n/16/160207gl.jpg.

Up close the heads were seen to consist of clusters of white, papery, scale-like items typical of the Amaranth Family, as shown at https://www.backyardnature.net/n/16/160207gm.jpg.

So here's another "variation on the amaranth theme," a little plant whose stems and leaves are profoundly different from the above Chamissoa Vine's, while the chaffy flower clusters are very similar.

In the above picture several fruits with their papery scales attached lie on the ground, maybe dropped there by rabbits nibbling on the heads -- rabbits because rabbit poop lay nearby and nibbling such heads is just something rabbits might do. Also, the pale clusters show up in the deep shade and, presumably the night, so I can visualize rabbits attracted to the heads glowing in moonlight, nibbling the heads. The plant might "want" the rabbits to nibble its heads, counting on some seeds getting dropped and thus disseminated. Whatever knocked those fruiting units onto the ground, a close-up of one of them appears on the tip of my finger at https://www.backyardnature.net/n/16/160207gn.jpg.

Our little plant is GUILLEMINEA DENSA, widely distributed but usually little reported from the US states south through Mexico, plus from Colombia to Argentina in South America. It's scattered in the US, where it's considered an invasive, plus it's "gone wild in southern Africa and eastern Australia. In Mexico it's found mostly in the north-central states, at the same latitude as the Yucatan, and in similar environments. It's described as most frequent on trails and in sidewalk cracks, so our plant was just where it belonged.

By the way, the full binomial name of Guilleminea densa  is Guilleminea densa (Humboldt & Bonpland ex Schultes) Moquin-Tandon, indicating that Alexander von Humboldt and Aimé Jacques Bonpland encountered it during their amazing expedition of discovery in tropical America from 1799 to 1804. Humboldt's account of that trip is fascinating reading, and can be downloaded for free at the Project Gutenberg site. I always have a little empathetic rush when I see the authorities "Humboldt & Bonpland" appended to the name of a plant turning up in my own life.

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TROPICAL ALMOND'S REDDENING LEAVES
Here during the early dry season many of our native trees as well as some introduced ones are losing their leaves, or are already completely leafless. The leaf drop is to conserve water during the upcoming rainless months, for leaves transpire water, even leathery, waxy-surfaced ones adapted for arid environments.

The Hacienda's Tropical Almond trees haven't lost their leaves yet, but their big, club-shaped leaves are turning red in preparation for it. The red leaves add a touch of fallishness to the landscape, even as other dry-season-leafless trees look wintry, and other dark, green, broadleaf-evergreen trees look summery. You can see what a gathering of red-turning Tropical Almond tree leaves looks like on a sunny day with a blue-sky background at https://www.backyardnature.net/n/16/160207tm.jpg.

Even among our introduced ornamental trees, such spectacular outbreaks of bright red leaves are rare around here. Their brilliance got me to wondering if there might be something special going on.

I learned that Tropical Almond leaves are describe as "chemically rich," and that they're used in many different herbal medicines for various purposes. The most frequently mentioned medicinal use is against dysentery and diarrhea in humans, and among tropical fish breeders in tropical countries often leaves are placed in the water to deal with fish parasites and bacterial pathogens. For a healthy aquarium, for each 100 liters of water, add three or four leaves in the water for four or five days. The online Agroforestry Database 4.0 mentions the red leaves can serve as a vermifuge -- against intestinal worms.

Though the leaves contain many compounds -- flavonoids, saponines, phytosterols and many tannins, I suspect that the bitter tannins provide most medicinal benefit, for they're astringent and cause tissue to pucker, which can seem useful during bouts of diarrhea. Tropical Almond's bark is especially high in tannins. The Agroforestry Database reports bark containing 9-23% tannin, which is pretty high.

Tropical Almond trees, probably native to tropical Asia, are planted in the tropics worldwide because they're handsome, thrive when neglected, and are useful if you know what to do with them. Our Tropical Almond Page is at https://www.backyardnature.net/yucatan/almond-t.htm.

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ELEPHANT EAR RHIZOMES
Back in 2010 when I planted Elephant Ears, Xanthosoma sagittifolium, in front of the hut, I never thought they'd grow so large and develop into a small forest. You can see how tall they grow on our Elephant Ears page at https://www.backyardnature.net/yucatan/elephant.htm.

Those pictures were taken in 2011, and nowadays the plants are just as large, and there's more of them.

I hadn't thought about them spreading so easily. It's not because their spectacular flower structures -- shown on the above page -- produce fruits with viable seeds, because so far all the flowering I've seen has resulted in aborted fruits. It's because the plants produce strong, wide-ranging rhizomes. The other day I pulled a young one from a spot where I wanted to plant something else and just had to admire the plant's thick roots and rhizome, shown at https://www.backyardnature.net/n/16/160207rh.jpg.

The rhizome is the thick, scaly item with a white tip, running horizontally across the picture.

Rhizomes are defined as modified subterranean stems that often issue roots and shoots from their nodes. In botany, the term node designates a stem joint where a leaf appears, or may appear at one time or another. A close-up of our Elephant Ears' rhizome shows a couple of nodes, at https://www.backyardnature.net/n/16/160207ri.jpg.

In that picture the lower node is sprouting a white bud from which later probably a shoot will arise, developing into a new plant. On each side of the bud arise brown, veiny, triangular scales. I think that they must be analogous to stipules on above-ground stems, stipules being modified leaves often occurring at petiole bases.

It's good to understand the rhizome and node concepts because when a rhizome is broken up each node may be able to sprout a new plant. That's good if you want to grow many plants from the rhizome of a particularly desirable mother plant, but bad if your plant is a weed you're trying to get rid of.

An interesting word applied to rhizomes is "diageotropic," which describes something that grows perpendicularly to the force of gravity.

Stolons are different from rhizomes because usually stolons run atop the ground. Also, rhizome nodes are close together, like ours, while stolon nodes are widely separated, like those on a strawberry plant.

Older Elephant Ears often develop pale, reclining trunks as thick as an arm, which lie atop the ground and, in very old plants, may stand up to seven or so feet high (2m). But those are regular stems, or trunks, not the rhizomes we're talking about.

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THE BANANA TREE'S STEM
At https://www.backyardnature.net/mexnat/banana.htm, on our Banana Page, so many things are said about banana plants that I figured we'd covered the subject. However, this week I was exploring a part of the woods where the gardeners had dumped an old banana tree they'd thinned from the plantation, and when I saw the tree's cut-through, foot-thick trunk, I just had to sit and study the matter. You can see what I saw at https://www.backyardnature.net/n/16/160207bn.jpg.

First of all, we need to be clear that what normally is called a banana tree is actually a short-lived, herbaceous shoot off a perennial rhizome that lives for years underground. The subterranean rhizome issues shoots that grow tall fast, flower and fruit, and then die, while the rhizome lives on. Maybe the best way to describe the "banana tree" is as a tree-like perennial herb. The trunk or stem of the tree-like perennial banana shoot is a false stem technically known as a "pseudostem."

So, in our picture you can see that a banana plant's pseudostem mostly consists of overlapping sections that in cross-section appear slenderly crescent-shaped. These are the banana leaf's tightly packed, overlapping leaf stems, or petioles, flattened at their edges into sheaths that partly wrap around other petioles. These leaf bases nest within one another in a spiraling manner. The solid part in the cross-section's center is the flower stalk extending up through the pseudostem, terminating at its top with a cluster of flowers and/or banana fruits.

Our picture shows that each overlapping leaf sheath displays interesting structural features, shown in more detail at https://www.backyardnature.net/n/16/160207bo.jpg.

Besides the sheaths conspicuous cross-walls and cells between the cross-walls, notice the fibrous nature of the sheaths' skins. On our banana page we show that these fibers are quite strong.

The remarkable thing is that even though the banana plant's pseudostem is fleshy and consists mostly of water, it's strong enough to support a bunch of banana fruits weighing well over a hundred pounds (50 kg). Also, banana plants are famously able to withstand strong winds. During hurricanes, their leaves and stems flap and gyrate, but usually don't break or get flattened. Seeing our pesudosem's inner architecture, I figured that I was witnessing some sophisticated engineering, so I looked into the matter.

At http://jxb.oxfordjournals.org/content/51/353/2085.full I freely downloaded a research paper published in 2000 in the Journal of Experimental Botany entitled "The functional morphology of the petioles of the banana, Musa textilis," by AR Ennos and others.

That paper makes the point that a general rule in engineering is that when rigid supports are slender, under heavy weights they tend to buckle, but when features are added to deal with the buckling, rigidity is lost and not much weight can be supported. Banana pseudostems are slender, rigid and resist buckling, so the authors thought it was worth trying to figure out how they did it.

The researchers, after extensive consideration of the banana plant's structural curiosities, ended their paper with, "In conclusion, it is the combination of the many distinctive features of the banana petiole into a clever integrated design that seem to confer its ability to be both rigid and deform reversibly downwind in gales."

In other words, if you want to build a slender support that's rigid enough to bear heavy weight yet also can withstand a great deal of wind stress and flapping around, go look at a banana pseudostem such as the one lying moldering on the ground near the hut.

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AN OPTIMISM OF BIRD MIGRATION
Friend Eric in Mérida sent a link to a New York Times article from last month bearing the title "Bird Watchers Help Science Fill Gaps in the Migratory Story." The heart of the article is an animated map created at Cornell University. On the map, each moving dot represents the flight of a different bird group during spring migration, mostly from the American tropics to summer breeding grounds in North America.

To create the map, researchers used data from more than a million observations made by amateur bird watchers and uploaded to the eBird website, an online, citizen science project. You can read the story and see the flow of birds northward -- many passing through the Yucatan before launching across the Gulf of Mexico onto US shores -- here. 

When you visualize birds actually making the heroic journey -- remember their nervous excitement building during the days before leaving, recall the old and infirm ones left behind looking so disconsolate, and the utterly exhausted ones dropping onto the beach after crossing the Gulf -- you think that the fluid motion of those dots moving northward is graceful as a ballet dancer portraying a swan, as beautiful as a newborn child awakening and looking around.

The map is even more significant when it really sinks in that each moment of each dot on the map represents data points that were achieved artfully, and by people with clear minds and generous intent.

For, each of the millions of observations was made by people who had practiced birding enough to recognize a species when they saw it; each observer at the moment of identification -- in the field and often under difficult circumstances -- was focusing through life's usual distractions and fog of clutter to the point that a moment in the field could be transformed into information online at the eBird site, and; each birder was generous enough in spirit to do all this without thought of payment, in fact usually at some expense to themselves. They did it just for the pleasure of sharing a moment, an insight, a new piece of information with others. A million times real facts such as a little brown sparrow among cattails on an obscure, mosquito-infested mud bank were crystallized into moments of a dot stuttering northward on that map.

Beyond the obvious prettiness of all this done exceedingly well, the map with its moving dots encourages a kind of transcendent optimism.

For, if something good and inspiring has crystallized in the context of so many of the bird groups represented on the map suffering drastic population decline, and in the face of other news from all over the globe of things and events that are anything but artful, clear minded, and generous in intent, then we have something encouraging.

In fact, maybe there's a Universal Law of Nature that when a kind or class or species of sentient being reaches an evolutionary threshold at which all members of that kind, class or species can share diverse thoughts -- as humans now can via cell phones and the Internet -- maybe something good happens. Maybe at first there's clutter and confusion, such as we see in the Internet's content now, but then comes consensus of insight as manifested by this map, and then, one hopes, enlightened action.

It seems to me, though, that just as likely is that there may be another Universal Law of Nature assuring that whenever some kind of sentient being reaches such an evolutionary threshold, it's unable to overcome the primal aggressions and insensitivities to other living things that enabled it to gain dominance over them... and extinguishes itself -- through war, inaction, or the workings out of mass psychoses.

For my part, whether or not such Universal Laws exist, I'm proceeding as if I believed that the bird map with its elegantly flowing data points is itself a tiny data-point on the Middle Path to universal enlightenment.

*****

Best wishes to all Newsletter readers,

Jim

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