September 30, 2012

HUMMINGBIRD MIGRATION MYSTERIES
Among birders often it's said that the best place in the US to see a variety of hummingbird species is southeastern Arizona. Some would say that western Texas is just about as good. Here in southwestern Texas we can see the East's Ruby-throats, we're on the eastern border of several Western species, plus we're at the northern extreme of the distribution areas of some Mexican species. In western Texas 16 of the 18 hummingbird species that show up in Texas can be seen.

You should see the circus all day long at my host's hummingbird feeders. In southern Texas the peak of hummingbird fall migration occurs around the first day of autumn, and nowadays if you can identify most of the birds at a typical feeder here -- with all the similar-looking females and the juveniles in various intermediate plumage phases buzzing around too fast to notice much about them -- you're a better birder than I. In fact, except in the rare case of having a mature adult male in summer plumage, to identify nearly all of what I see here I must photograph them, get the picture onto my laptop screen, then do a lot of studying in field guides. For example, this week I shot the picture at https://www.backyardnature.net/n/12/120930hu.jpg.

Unlike most at the feeder, that bird at least has the beginning of a splotch of a red throat, so the possibilities are much reduced. The lack of rusty coloring on the chest and back also limit the possibilities. The other definitive field mark is the tail, which is somewhat forked.

For me the question is whether this is a Ruby-throated or Broad-tailed Hummingbird. I'm told that Broad-tails are the most common here, outnumbering Ruby-throats, which are only migrants, ten to one.

However, after comparing many pictures on the Internet with our image I'm thinking this is a migrating Ruby-throat, because Broad-tailed Hummingbird tails are rounded, not forked. I read that male Ruby-throats begin moving through Texas the first week in July, then females and juveniles follow in August and September. If anyone out there disagrees with the ID, let me know.

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A BLACK SWALLOWTAIL CATERPILLAR'S OSMETERIUM
My host gave me four large, healthy parsley plants, quipping that Black Swallowtail caterpillars really love to eat them. They'd defoliated the plants three times this year already, and now transplanted at the cabin for the fourth time they're losing their ferny leaves to about a dozen plump, zebra-striped Black Swallowtail caterpillars, one of which is shown at https://www.backyardnature.net/n/12/120930cu.jpg.

These are such handsome caterpillars, and the butterflies into which they metamorphose are so beloved and pretty, that we just let them have their way with the parsley. The parsley grows back; the butterflies' survival is more critical. And how could anyone kill a caterpillar with a face such as that shown at https://www.backyardnature.net/n/12/120930cv.jpg.

Swallowtail caterpillars are equipped with an orange, forked gland called the osmeterium which, normally hidden, emerges from the segment behind the head when the caterpillar feels endangered. The osmeterium releases a foul smell to repel predators. The chemicals exuded from the osmeterium varies from species to species.

The chemicals of our parsley-eating caterpillars smell somewhat of parsley. I know that because I just stepped outside, annoyed a Black Swallowtail caterpillar by tapping it on its side, causing his osmeterium to appear, and the caterpillar turned around and pressed the osmeterium onto my offending fingertip, which I then smelled of. You can see the upset caterpillar with orange osmeterium deployed at https://www.backyardnature.net/n/12/120930cw.jpg.

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SETWING DRAGONFLY
On a hot, dry, windy, sunny afternoon a dragonfly perched on a tomato-plant cage in the garden, looking a bit out of place in such a dusty spot, though the little Dry Frio River ran only two or three stone-throws away. You can see the little critter at https://www.backyardnature.net/n/12/120930df.jpg.

The unusual feature of this species was that he perched with his wings set forward, instead of straight out like a biplane's wings or a typical dragonfly's. I made sure to get the wings in sharp focus, for in dragonfly identification wing venation is very important.

Using the "Dragonflies through Binoculars" field guide for North American dragonflies I decided that my garden visitor must be the Swift Setwing, DYTHEMIS VELOX, distributed mostly in the US Southeast and the south-central states, but as far north as southern Missouri, and south into central Mexico. Species in the genus Dythemis are called setwings because of their curious manner of setting their wings forward.

However, when I count the number of cells in the front wing between the dark cell near the wingtip (the "stigma") and the little notch about midway in wing (the "nodus") there are more cells than other wing-pictures of the species show. I uploaded our picture to Bugguide.Net where another dragonfly enthusiast using a different book confirmed that, despite the extra cells, it could hardly be anything other than a Swift Setwing. So, it seems that my garden visitor is something of an anomaly. However, in Nature anomalies are permitted, if not outright encouraged.

The book says that Swift Setwings are particularly common in Texas and that they are extending their ranges northward. They are described as feeding from twigs along forest edges. Males "...perch on twigs near the water's edge, sometimes high and in shade, on hot days obelisking vertically."

"Obelisking," I was gratified to learn, is merely sticking the rear end, or abdomen, skyward. This would reduce the amount of sunlight heating the abdomen.

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FISHING SPIDERS
Sprawled two inches (5cm) across an autumnal sycamore leaf floating atop the little Dry Frio River's clear surface, an unusually big, tan-colored spider with white racing strips on the cephalothorax and white spots on the abdomen basked in the afternoon sun, as shown at https://www.backyardnature.net/n/12/120930fi.jpg.

About two feet away similarly floating atop a shed Chinese Tallow Tree leaf a darker-brown spider also with racing stripes and white spots, but only about half the size and darker, squarely faced the big spider while seemingly being ignored by the larger spider. The smaller spider is at https://www.backyardnature.net/n/12/120930fj.jpg.

These were Six-spotted Fishing Spiders, DOLOMEDES TRITON, fairly common throughout the Western Hemisphere. They're also called raft spiders, dock spiders and wharf spiders. In the pictures, the big one is the female and the little one the male. Fishing spiders do sometimes catch and eat small fish and tadpoles, but the more normal fare is insects and other invertebrates. They're excellent divers, submerging and grabbing onto a plant when feeling threatened, plus they can dive over seven inches (18cm) to catch prey.

The little male has good reason for keeping his distance, despite his apparent interest in the big female. This is one of those species in which cannibalism occurs -- the female eating the male after mating, the male thus contributing the protein and nutrients in his body to the next generation.

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LITTLE WALNUT
Beside the little Dry Frio River running behind the cabin, at the edge of a low terrace of limestone cobbles deposited by floodwaters long ago, at first I thought a cluster of pale-barked, little trees about 15 feet tall (4.5m) were Pecan trees that had been much battered and splintered by fast-running water, as shown at https://www.backyardnature.net/n/12/120930jw.jpg.

Up close, the pinnately compound leaves with scythe-shaped leaflets brown and shriveling with autumn coming on might have been Pecan leaves, but the small, black, spherical fruits certainly were not Pecan fruits, which are elongated. You can see our tree's leaves and spherical fruits at https://www.backyardnature.net/n/12/120930ju.jpg.

Keep in mind that the picture's right side is dominated by just one compound leaf rising vertically, bearing several pairs of slender leaflets. The compound leaf arises from a thick twig entering the picture at the bottom, right. A fruit with its husk partially removed is shown at https://www.backyardnature.net/n/12/120930jv.jpg.

If the husk of this fruit were that of a Pecan or any other hickory fruit (genus Carya,) the husk would show cleavage lines or sutures running at least part of the way from the fruit's tip to its base, but this husk indicates no such line. That means that this is some kind of walnut, genus Juglans. North America's several hickory and walnut species are the only members we have of the Walnut Family, the Juglandaceae, and our fruit is a walnut because the nut's husk doesn't split partially or entirely at maturity. So here was a new walnut species I'd never seen before, at that was exciting!

In the online Flora of North America it was easy to "key out" the species because their fruits are exceptionally small to be a walnut -- only about 7/10ths of an inch across (1.8cm). Our tree is called the Little Walnut, JUGLANS MICROCARPA, the "microcarpa" referring to the small fruits. The species extends from arid northern Mexico up through Texas as far north as southern Kansas, and into New Mexico. Flora of North America says that it occurs along creeks and rivers, exactly as we find it here.

Apparently the profuse sprouting from the trunk from which previous large branches have broken off represents an adaptation to violent flash flooding of creeks and rivers in our arid area. It seems that if you're a tree in such an environment either you can be supple like a willow, or brittle and quick to resprout new branches, like our Little Walnut.

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NETLEAF HACKBERRY
On rocky limestone outcrops hemming in the little Dry Frio River nowadays you see medium-sized trees loaded with pea-sized, red fruits, as shown at https://www.backyardnature.net/n/12/120930ce.jpg.

The small fruits are drupes, which means that they are fleshy, one-seeded fruits that do not split open at maturity, and that the seeds are enclosed in a woody shell, the endocarp. Such hard-shelled seeds are often called stones. Cherries, plums and peaches are drupes with stone-type seeds. The red fruits in the picture are surprisingly sweet and tasty, though the flesh covering the seeds is so meager that most people wouldn't bother nibbling on them. Of course birds eat great quantities of them. You can see some fruits and their seeds at https://www.backyardnature.net/n/12/120930cf.jpg.

The tree's very warty bark is shown at https://www.backyardnature.net/n/12/120930cg.jpg.

If you know your trees you probably recognize that this is some kind of hackberry or sugarberry, but which one? North America is home to six hackberry/sugarberry species -- members of the genus Celtis -- and sometimes distinguishing them can be hard. Also, several Celtis species hybridize, and in general Celtis taxonomy is in a mess.

However, the red fruits and the 1¾-inch long leaves (4.5cm) -- unusually small for a hackberry/sugarberry -- with their smooth margins lacking serrations, and with the blades' pronounced netlike venation, all are good field marks helping us identify this as the Netleaf Hackberry, sometimes called the Western Hackberry, Canyon Hackberry and Palo Blanco. It's CELTIS RETICULATA, mostly distributed in the arid southwestern US, though in the mountains it extends as far north as southeastern Washington state.

Birds, squirrels, foxes, coyotes, and other mammals eat the sweet fruits, and White-tailed Deer and cattle out on the range browse the leaves and young stems. The USDA rates Netleaf Hackberry browse as a good source of protein.

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FROSTWEED
You can see one of the most common and conspicuous wildflowers blossoming nowadays along roadsides and trails and at woods edges at https://www.backyardnature.net/n/12/120930vb.jpg.

Around here that's called Frostweed because, I'm told, during winter's first good freeze conspicuous white "wings" of ice emerge from the stem, something very pretty to see. The plant also is known at White Crownbeard, Indian Tobacco, Iceplant and Wingstem. It's VERBESINA VIRGINICA, found throughout the US Southeast and adjacent states. You can see that Frostweed is a member of the Composite or Sunflower Family at https://www.backyardnature.net/n/12/120930vc.jpg.

That picture shows five flower heads, each head bearing two to four flat, petal-like "ray flowers" surrounding a dozen or so tubular, five-lobed "disk flowers." Each brown item arising from a disk flower is composed of five anthers fused by their margins into cylinders surrounding the flowers' styles, or ovary "necks." The styles fork at their tips into two curved-back stigmatic areas -- where pollen germinates. These are all features of members of the enormous Composite Family.

One good field mark for Frostweed is that in its flower heads the ray flowers are not at all evenly spaced on the perimeter. In the last picture on the bottom flower head notice how three ray flowers crowd the left side but only one arises on the right. The combination of such asymmetrical flower heads with the brown anthers giving the clusters a salt-and-pepper look is distinctive of the species.

A shot showing the clusters' involucral bracts, which are especially long, hairy, and not much overlapping one another, is at https://www.backyardnature.net/n/12/120930vd.jpg.

Another very distinctive feature of the species, as well as several other species in the genus, is that the stems are provided with green "wings" of leafy material, as shown at https://www.backyardnature.net/n/12/120930ve.jpg.

Probably those leafy wings have something to do with the "ice wings" developing during the first hard freeze. They're certainly responsible for one of the plant's more popular names, Wingstem.

Several traditional medicinal uses of Frostweed, or Wingstem, have been documented among Native Americans. Depending on the culture, the plant has been used as a gastrointestinal aid, a urinary aid, a laxative, an eye medicine, externally against joint pain, as an emetic, and for ceremonial uses.

Ecologically Frostweed is an important nectar provider. As I photographed the plant several butterflies of various species visited the flowers. In early morning if you find a place where lots of Frostweeds are flowering in the sunlight, the place will be alive with butterflies.

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MEALY SAGE
When I arrived here a pretty, purple-flowered mint grew in several places along my garden deer-fence so I assumed it had been planted by the previous tenant. You can see a flowering sprig of it at https://www.backyardnature.net/n/12/120930sg.jpg.

As soon as I began wandering around, however, it turned up on limestone slopes along the river and elsewhere, so maybe it was native. Now I've figured it out. Take a look at a flower and see if you can guess what famous group of Mint Family plants it belongs to, at https://www.backyardnature.net/n/12/120930sh.jpg.

It's a sage! It's the Mealy Sage, or Mealycup Sage, SALVIA FARINACEA, the Mealy part of its name referring to the white, clumpy fuzz on the flower's calyx and upper stem. Another unusual feature of the flower is the covering of long, blue hairs on the corolla's upper lip, and the white spots on the broad lower lip.

It turns out that Mealy Sage is a native wildflower pretty enough for horticulturalists to have bred several cultivars from it, such as the 'Blue Bedder,' which only grows to about 1 ft (0.3 m) high, and the most popular one, 'Victoria', which becomes a bushy mound about 2.5 ft high (0.8 m).

In the wild Mealy Sage is distributed through northern Mexico and the arid south-central US states.

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TEXAS'S STATE GRASS
In a variety of habitats, but especially on limestone outcrops along the little Dry Frio River behind the cabin, there's a certain knee-high clumpgrass fruiting in a very conspicuous and unusual manner nowadays. You can see a clump with the Dry Frio's shallow waters in the background at https://www.backyardnature.net/n/12/120930bt.jpg.

The "slender pagoda" effect, with the clusters of spikelets hanging downward -- "pendent," as botanists say -- is a fine field mark. And this is a grass worth knowing since it's one of the main native short-grass prairie species throughout the Americas, from Canada to Argentina. It's so important for grazing cattle that it's the State Grass of Texas. Usually called Sideoats Grama, it's BOUTELOUA CURTIPENDULA.

In Texas Senate Concurrent Resolution #31, among several "whereases" explaining why Sideoats Grama should be the state grass, there's the following:

You can read Resolution #31 in its entirety at http://www.netstate.com/states/symb/grasses/tx_sideoats_grama.htm.

If you're familiar with grass-flower structure you'll recognize that Sideoats Grama's flowering and fruiting heads are a bit unusual. You can see some up close at https://www.backyardnature.net/n/12/120930bu.jpg.

You can review glass-flower anatomy on our grass page at https://www.backyardnature.net/fl_grass.htm.

The tricky thing with Sideoats Grama flowers is that each compact, pendent item in the picture is not a spikelet but rather a cluster of spikelets. In grass-talk, a spikelet is a unit holding one or more florets (flowers). For most grasses such clusters are spikelets, but Sideoats Grama crams one to eight spikelets into a cluster, and then each spikelet contains one or two florets. Also, in most grasses once the achene-type fruits are ready to fall, either a floret falls from its spikelet, or a spikelet falls from the stem, but with Sideoats Grama the whole group of spikelets falls as a unit.

So, this is one of the most important flowering native plants in the Americas, yet few people have heard of it. It occurs throughout the US and much of Canada, though in Kentucky and Mississippi I saw it only rarely, normally in especially dry natural areas. Really, Sideoats Grama prefers drier habitats than normally found there.

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COMPOST BIN MADE OF SHIPPING PALLETS
At this new location I'm favored with having neighbors who have lots of straw they're eager to have removed from their freshly mowed properties, and other neighbors glad to rid themselves of horse and chicken manure, and yet another neighbor with an excess of unneeded shipping pallets. To me this situation means one thing: Good composting potential. You can see my newly wired-together compost bin made of shipping pallets at https://www.backyardnature.net/n/12/120930cm.jpg.

On the left I've forked in seven double layers of alternating hay and manure. After depositing each double layer I soaked it with water. The picture was taken a couple of weeks ago and I water the heap from time to time, keeping in mind that when the compost turns black and smells like a sewer it's too wet, and when the straw turns white, it's too dry. Occasionally I dig into it to see how things are going and I'm always impressed by the heat, in some places so intense I can't hold my hand there for long. The heat is caused by microbes doing their jobs of decomposing the heap. During two weeks the heap has diminished by about a quarter of its size in the picture, as hay and manure gradually becomes compost.

The bin has three compartments because once the decomposition slows down and there's less heat produced in Bin #1 I'll pitchfork the whole heap into the middle bin, placing straw that's been on the heap's outside -- and thus not getting "cooked" like straw inside the heap -- inside. Redoing the heap also aerates the whole thing. This will cause the "cooking" process to start all over.

The aeration is important. You can think of composting as following a recipe in which you have to balance just right the ratio of carbon (carbohydrates in the hay) with nitrogen (urea and other nitrogenous compounds in the manure), plus water and air. If any of these four major ingredients is missing or not of the right amount, good composting won't take place. Once the heap is reconstituted and its decomposition is begun again in the second bin, a new heap of fresh straw and manure will be piled into the first bin. Eventually the entire forking and reconstitution routine will be repeated, moving both heaps to the right. At the end of that cycle, what comes out of Bin #3 will be high-quality, spongy, nutrient-rich, sweet-smell compost.

In those black bags at the right in the picture is chicken manure. That's such powerful stuff that I keep it aside for side-dressing leafy crops needing nitrogen.

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FEATURED ESSAYS FROM THE PAST:

"Why I'm Against Nuclear Power," from the December 22, 2008 Newsletter, at https://www.backyardnature.net/n/p/081222.htm.

"Why Bother with Preserving Species?" from the November 21, 2010 Newsletter, at https://www.backyardnature.net/n/p/101121.htm.

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Best wishes to all Newsletter readers,

Jim