JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from the valley of the Dry Frio River on the
southern slope of the Edwards Plateau, northern
Uvalde County, southwestern Texas, USA

March 24, 2013

GOLDEN-CHEEKED WARBLER
About mid slope on the limestone hill to the east I heard the call of what seemed to be a migrating Black-throated Green Warbler, but the call was a variation I'd never heard before. I've heard lots of Black-throated Greens singing as they passed through the eastern US between their nesting grounds in North America's northern coniferous forests and their overwintering area in Mexico, Central America and northern South America. Often during migration they're the main bird you hear, the typical song sounding something like zoo-zee, zoo-zoo-zee, repeated again and again, and there might be so many of the calls coming from all different directions that it can be funny to hear.

But, this call was the most extreme variation on the Black-throated Green Warbler theme I'd ever heard. In fact, it was so unusual that I wanted to see this bird, just to be sure my mind wasn't playing tricks. And I did see him, just for an instant when he flew into an Ashe Juniper not far away, as witnessed at http://www.backyardnature.net/n/13/130324wb.jpg.

That bird certainly has the Black-throated's black throat, the yellow cheeks and white wingbars but, still, I decided to check to see if there were other closely related species in this area that might have a different call. And there was:

The Golden-cheeked Warbler, DENDROICA CHRYSOPARIA, is almost identical to the Black-throated Green Warbler, except that its back is black instead of olive green, the lines passing through its eyes are blacker, its song is similar but clearly different and... it's an officially endangered species, both in the US and on the IUCN Red List. Golden-cheeked Warblers nest only in central Texas's mixed Ashe Juniper and oak woodlands, in ravines and canyons -- in the whole world only in our little area -- where they feed on insects and spiders on tree leaves and bark.

The IUCN page for the species says that " ...the population was estimated to number 21,000 individuals in 2004... There was a 25% loss in available territories between 1962 and 1981 ..., and the population has clearly declined. It winters in southern Mexico (Chiapas), Guatemala, El Salvador, Nicaragua, and Honduras... " The IUCN Red List for the Golden-cheeked Warbler is at http://www.iucnredlist.org/details/106009107/0.

I sent our picture to my old birding buddy Jarvis, who has a PhD in Ornithology, and he thinks our bird probably is indeed the Golden-cheeked Warbler, not only because we're exactly where the bird should be right now, in the exact habitat, and because the song I heard was like the Black-throated Green's song but not quite, but also because the black line barely detectable in our bird's picture is about right for the Golden-cheeked, and too dark for the Black-throated. Also, now that I've compared our bird with many pictures, it seems to me that the blackness of our bird's throat extends over the front of the shoulder in a way it doesn't on the black-throated Green. I just wish I could have seen that black back!

*****

HARRIER HARRYING
All winter a certain long-tailed, low-flying hawk has patrolled the Dry Frio Valley's grassy fields occasionally swooping and pouncing on rodents espied hurrying down raceways between clumps of grass. I've tried many times to photograph the bird but he flies so low that he's upon you before you know it and by the time the camera is ready he's gone, or else nearby and moving so fast you can't focus on him. This week, however, I just happened to see him coming, so I got what's shown at http://www.backyardnature.net/n/13/130324ma.jpg.

The shot on the left shows the bird's owl-like face with eyes set forward in a way that provides binocular vision, thus enhancing depth perception. Good depth perception is needed for catching rodents scrambling through grass. That picture also shows an unusual feature of how this species flies: its wings held well above the horizontal. The image at the right shows the bird's exceptionally long tail. However, neither picture shows what may be the most vivid field mark of all, which is the white "rump" -- the rump being the lower back just above where tail feathers attach.

I grew up calling this the Marsh Hawk because that's how early bird field guides in the US identified them, but over the years most guides seem to have gravitated to the name Northern Harrier. "Harrier" and "Hen Harrier" are names used in Europe, where the species also occurs. In fact, our Northern Harrier enjoys an usually large distribution area, occurring all across North America and Eurasia. During the winter Eurasian birds migrate into southern Europe and southern temperate Asia while American breeders overwinter in the southern US, through Mexico and Central America, into northern South America.

Northern Harriers, CIRCUS CYANEUS, are unusual hawks. In field guides typically they're listed separately from slender-bodied, long-tailed, rounded-winged "accipiters" such as the Cooper's and Sharp-shinned Hawk, as well as apart from the "buteos" with their broad, rounded tails and thick bodies, such as the Red-tailed and Broad-winged hawks. When you see how consistently low-flying the bird is, and how owlishly he looks at you as he glides past, it's easy to believe he's something special, something different from the usual hawks we see. One other feature unusual for a hawk is that among Northern Harriers males and females are colored differently: Males are predominantly gray while females are brown. Our bird is clearly a male.

I'm glad I finally got this picture, for soon Northern Harriers will disappear from our grasslands and won't return until fall, after nesting is finished far to the north.

*****

TURKEY WING DRAG-MARKS
Last month we noted that Wild Turkeys are strutting here. They continue doing so, and one morning this week the little gravel road passing by the cabin was found to be marked with many scratchings such as those appearing at http://www.backyardnature.net/n/13/130324tk.jpg.

Especially on the picture's right side you can make out some toe marks left by a strutting turkey, but the main scratches are the wavy lines along both sides of the footprints. The wavy lines are called wing drag-marks because they're formed when the strutting tom droops his wings so that they scrape against the ground as he walks forward. I guess that dragging stiff wings across a gravel road's fairly hard surface makes considerable noise and maybe throws up some dust, which might impress attentive females. And of course the idea behind strutting is for the tom to display his strength, vigor and enthusiasm.

Turkey hunters know all about Wild Turkey wing drag marks and believe that when they're discovered the good hunter will return later in the hope that turkeys will be revisiting the same spot. However, until that one morning this week there'd been no such markings on our road earlier this season, and none since. But, that morning, there must have been twenty or so such scratchings.

*****

FLOWERING CATCLAW
In very thin, dry soil atop our rocky-topped, limestone hills you find plants not growing below on the slopes or in the valley. The plants are highly adapted to alkaline soil that's normally extremely dry, and to temperature extremes and abundant sunlight. Nowadays atop the limestone hill to our south there's a wiry, spiny bush or small tree a little over head high issuing its leaves and opening its flowers, as you can see at http://www.backyardnature.net/n/13/130324ac.jpg.

Notice at the picture's bottom the thick-based, backward projecting, low spines. Also, occupying the picture's lower, left quarter you can see the tree's twice-compound leaf -- a single leaf in which the primary divisions are themselves divided into small leaflets, or pinnae. A shot better displaying a leaf's basic structure and conveying its smallness is at http://www.backyardnature.net/n/13/130324ae.jpg.

The plant's spherical, white, fuzzy flowering heads consist of numerous closely packed flowers. A cross-section of a head is shown at http://www.backyardnature.net/n/13/130324ad.jpg.

In that picture the reddish things are the flowers' calyxes, each calyx bearing five red, sharp-pointed sepals. If you look closely you can see that each calyx surrounds the base of a cream-colored or very pale yellow corolla with five lobes. The white, fuzzy things issuing from inside each corolla are stamens tipped with tiny, yellowish, globose, pollen-producing anthers.

In the Yucatan we learned that spiny trees with such twice-pinnate leaves and flowering heads composed of closely packed flowers containing more than ten stamens... is an acacia. But there are many acacias, over 1300 according to some estimates, and their taxonomy is in much debate, so figuring out that you have an acacia still leaves you a long way from enlightenment.

Judging from lists of species collected in our area and pictures on the Internet -- for the Flora of North America's acacia section isn't finished yet -- our currently flowering acacia appears to be ACACIA ROEMERIANA, known by several English names, including Roundflower Catclaw, Roemer Acacia, Catclaw Acacia and just Catclaw. Many different species of bushes and small trees with backward pointing, broad-based spines are called catclaws.

Our Acacia roemeriana is semi-evergreen, with woody stems presently mostly leafless, but with a few of last year's dark-green leaves still attached to lower stems, even as new leaves unfold along with the opening flowers.

As with other acacias, this one's small flowers produce nectar much appreciated by a variety of bees and other pollinators.

Acacia roemeriana is described as living on dry soil of limestone hills in southern Texas, New Mexico, and arid northeastern Mexico.

*****

NETLEAF HACKBERRY FLOWERING
Last September we got to know the Netleaf Hackberry's sweet, red drupes, which you can see and read about at http://www.backyardnature.net/n/w/celtis-r.htm Now that species' branches are burgeoning with fast-expanding leafy stems and flowers, as shown at http://www.backyardnature.net/n/13/130324hc.jpg.

A close-up of a shoot freshly emerged from a twig's terminal bud is seen at http://www.backyardnature.net/n/13/130324hb.jpg.

There you can see the hackberry's leaves nicely three-veined from the blade base the way a hackberry leaf should be. At the base of each leaf petiole arises a whitish, tongue-shaped, leaf-like stipule, which more or less embraces the embryonic leaf and flowers, protecting them from the elements during their most vulnerable time. Single flowers arise in angles formed where the petioles attach to the stem. Each flower consists of a shiny, pear-shaped, green ovary topped by two white, fuzzy, rabbit-ear-like styles. Pollen lands on the styles' fuzzy parts -- the "stigmatic" areas -- germinates, and the male sex germ migrates in a pollen tube from the pollen grain through the styles into the ovules inside the ovary. The ovary becomes the future fruit while ovules mature into seeds. In the flowers in the picture, below the green ovaries you can see the withered male parts -- yellow-brown anthers, which already have shed their pollen.

Curiously, flowers lower down the freshly emerged, elongating branch sprouts often are strictly male -- ovaries are missing and there are only stamens consisting of whitish, fingerlike filaments topped with greenish anthers. A picture showing a female flower with its white, rabbit-ear styles in the top, left corner, and a flower with only five stamens in the lower, right corner, is seen at http://www.backyardnature.net/n/13/130324hd.jpg.

Netleaf Hackberries are very similar to the southeast US's Sugarberry trees. In fact, earlier Netleaf Hackberries were regarded as mere varieties of the Sugarberry, and sometimes it can be hard to distinguish the two species. Both species are to be found in this area. However, Netleaf Hackberry's new stems, its flower pedicels and leaf petioles all bear a soft, white, wooly hairs, while the same newly emerged parts of the Sugarberry usually are not nearly so hairy. They may be somewhat hairy, but that hairiness soon disappears, and is not as conspicuous as shown in our pictures.

By the way, last September we were eating the Netleaf Hackberry's sweet, red drupes. Now in March many trees still bear numerous fruits, though now they are brown. However, they are still sweet, and I can't pass a tree without sampling a few. It's a mystery to me why the area's birds have not consumed them all.

*****

SACAHUISTA
Last September we profiled a plant sometimes known as Devil's Shoestring, growing in thin soil and limestone cracks atop a nearby hill. It looked like a bathtub-size clump of grass, except that its blades were stiff and edged with sharp, low spines. Also, arising from the clump's center was a long-stalked head bearing numerous inflated, three-cornered capsular fruits. You can see all this at http://www.backyardnature.net/n/w/nolina-l.htm.

This week, not far from the Devil's Shoestring and in the same habitat, a smaller but still substantial bunch of stiff, grasslike blades turned up with a flowering head of many small, white flowers issuing from the clump's center. Its leaves were not spiny edged and the flower head lacked a long stalk, but otherwise it seemed looked similar to Devil's Shoestring. You can see my Estonian lady-friend Malle providing scale for the plant at http://www.backyardnature.net/n/13/130324bg.jpg.

A shot of the plant with no human included is at http://www.backyardnature.net/n/13/130324bh.jpg.

A close-up of the short-stalked panicle of flowers is shown at http://www.backyardnature.net/n/13/130324bi.jpg.

And a close-up of an individual flower with conspicuous yellow anthers is at http://www.backyardnature.net/n/13/130324bj.jpg.

Devil's Shoestring was Nolina lindheimeriana, endemic to just a few counties in southwestern Texas. What we have here is NOLINA TEXANA, a member of the same genus, and known by such English names as Texas Sacahuista, Texas Beargrass, Basket Grass, Sacahuista and Bunchgrass. Despite "grass" being part of so many of its names, it's not a grass -- not a member of the Grass Family -- but rather is classified in the Lily, Agave, or other closely aligned family, depending on your expert.

So here's yet another pretty, drought-tolerant, native plant worthy of being planted in gardens and around homes. In fact, some garden supply stores do stock it. As one supplier says, "In-the-know professional landscapers use this tough-as-nails beauty like an evergreen grass."

Sacahuista is distributed from central Texas and New Mexico through arid Mexico into Guatemala.

*****

SOUTHERN DEWBERRY FLOWERING
During my Mississippi days I ate my share of dewberries produced by the trailing, spiny-stemmed Southern Dewberry, Rubus trivialis. You can see the plant and its luscious fruits at http://www.backyardnature.net/n/w/dewberry.htm.

Most of the landscape here is too dry for dewberries, but this week I was gratified to see along the little Dry Frio River's moist, weedy banks a few Southern Deweberries flowering, as shown at http://www.backyardnature.net/n/13/130324ru.jpg.

We're at the western extreme of Southern Dewberry's distribution, which occurs throughout the US Southeast. Around here it's the only dewberry species but in much of the Southeast there are other species. The Southern Dewberry differs from those by its stems bearing not only thick-based, slightly curved spines, which several other dewberry species also bear, but also shorter, thinner, straight spines tipped with tiny, spherical glands.

*****

EATING SOW THISTLE
All winter little rosettes of Prickly Sow Thistle leaves speckled the ground next to the cabin. With warmer weather the leaves expanded rapidly and now some of the plants are about knee high, producing yellow, dandelion-like flowers and white, puffball heads of parachuted, achene-type fruits. We profiled Prickly Sow Thistle in December, before freezes and the neighbor's cow removed the taller ones. You can see what they looked like then as well as now at http://www.backyardnature.net/n/h/sonchus.htm.

Nowadays only the plants growing right against the sunlight-reflecting wall are as mature as the ones in those pictures. Most plants are only about a foot tall or smaller, without flowers or fruits. Thing is, such foot-tall plants are perfect for harvesting to eat. One of them is shown at http://www.backyardnature.net/n/13/130324so.jpg.

A salad bowl heaped with freshly cut sow thistles is shown at http://www.backyardnature.net/n/13/130324sp.jpg.

And an afternoon snack of sow thistle greens accompanied by mashed potatoes and salad made from garden pickings and sprouted lentils is on display at http://www.backyardnature.net/n/13/130324sq.jpg.

Picking Prickly Sow Thistle is ticklish because the leaves' spines are just hard enough to cause discomfort, but not hard enough to stick you. With cooking they become so tender that in the mouth you hardly notice them. Cooked sow thistle is very much like cooked kale, and I prepare it the same way:

Pour about a finger's-width of water in a pot, cram it with leaves and put a top on it, and after the water has boiled about ten minutes and you feel the leaves are soft enough to eat, add some salt and paper, pull them out, pile them on a plate, top it with some margarine while it's still hot, and eat.

You can just feel vivacious nutrients streaming into the body, and the stomach saying "thank you."

*****

DINOBRYON: A WHOLE OTHER KIND OF ALGA
During this week's safari into a drop of water from the little Dry Frio River behind the cabin, I came upon a speck of debris suspended in the water. A treelike structure of a kind I'd never seen before arose from the debris, slowly undulating in microscopic currents like a large elm tree in a lazy summer breeze, as shown at http://www.backyardnature.net/n/13/130324db.jpg.

The entire branched structure was about 250 microns long, or 0.25mm, or 1/100th of an inch. I had no idea where to begin with the identification process, but by using a search engine image-search feature and the keywords "freshwater microscopic branched," after only three or four pages of thumbnail images I saw our unknown. To my vast surprise it turned out to be an alga, very unlike the filamentous or one-celled, freely floating algae species we've seen until now. Judging from pictures and lists of algae found in our area, I'm thinking our branched alga is a member of the genus DINOBRYON, though I wouldn't say which species. Dinobryon divergens appears to be especially common in our area, and looks like ours, so that name would be a good educated bet.

The genus Dinobryon is described as comprising species of freshwater algae forming colonies. In Dinobryon, each vaselike section of the branching colony is known as a "lorica," which is defined as a tubular, conical, or vaselike structure secreted by some protozoans and many rotifers. Each lorica contains a flattened, yellow-brown, photosynthesizing chloroplast, clearly visible in our image. When the alga cell inside its lorica divides, it rises to the rim of its lorica, grows a new lorica, and this is how the colony grows. If a lorica or group of loricae become detached from the colony, it can start a new colony.

Dinobryon photosynthesizes its own food, but under low light conditions can feed on bacteria and diatoms. Watching our Dry Frio colony sway back and forth, it seemed that its loricae were filtering the water in search of such food.

Dinobryon is one genus of about 33 genera included in the Golden Algae Family, the Chrysophyceae. Golden algae are capable of releasing toxins that affect gill-breathing aquatic organisms such as fish and clams. Golden algae grow rapidly and can out-compete other algae for nutrients, causing "blooms" during which enough toxins are released to kill fish and other gill breathers. The toxins cause fish gills to bleed and lose their ability to absorb oxygen, so the fish die of asphyxiation.

A 2011 report out of Baylor University states that along the Brazos River in north and central Texas, at least seven million fish have been killed since 1988 due to high golden algae levels. In 2005 more than a million fish died in Lake Whitney over a three-month period.

*****

FEATURED ESSAYS FROM THE PAST:

"Tadpole-Inspired Thoughts About Life," from the August 11, 2002 Newsletter, at http://www.backyardnature.net/n/p/020811.htm

"Tadpoles Over the Edge," from the September 1, 2002 Newsletter, at http://www.backyardnature.net/n/p/020901.htm

*****

Best wishes to all Newsletter readers,

Jim

All previous Newsletters are archived at http://www.backyardnature.net/n/.

Visit Jim's backyard nature site at http://www.backyardnature.net