October 9,  2011

YELLOW-HEADED VULTURE
Most days this week, right before dawn, it began raining, then on and off during the rest of the day showers moved in off the Caribbean keeping things wet. However, for a couple of hours Wednesday morning the sun came out and not only I but also the birds emerged to enjoy drying out. Among birds perching in early-morning sunlight beside the white sand road was the one at https://www.backyardnature.net/n/11/111009yv.jpg.

Vulture, yes, but not like the ones usually seen here. In the Yucatán we have four vulture species. The most commonly seen is the Black Vulture, the stubby-winged one with white patches on his wing undersides. Also common are Turkey Vultures, with longer wings, all-black plumage, and fingerlike feathers spreading at the tips of narrower wings. Very rarely one sees mostly-white King Vultures. And then there's the fourth species, the one in our picture.

Vultures have featherless, or "naked," heads so gunk doesn't get stuck behind feathers as the heads withdraw from carrion. Skin on the head of adult Black vultures is black, while head skin of adult Turkey Vultures is red. We don't have a mostly-white King Vulture, so that leaves us noticing that the skin on our vulture's head is partly red like a Turkey Vulture's, but also there's a good bit of yellowish orange and some whiteness.

This is an immature Lesser Yellow-headed Vulture, sometimes called Savanna Vulture, CATHARTES BURROVIANUS. It's resident from southeastern Mexico south through Central America to northern Argentina in South America. The species' habitat preferences are listed as marshes, savannas, open grasslands and mangroves. They're shown as existing throughout the entire Yucatan Peninsula, but I've only seen them along the coasts, and nowhere commonly, though this week I've seen several here.

Mature Lesser Yellow-headed Vultures lack the white shown in our immature's face. They have the orange, but then also there's a broad bluish-purple band at the bill's base, a pale blue crown, and a blood-red nape band. Adults show little of the pinkishness seen on our immature. I'm going into detail here because in A Guide to The Birds of Mexico and Northern Central America Howell reports the juvenile plumage as undescribed, guessing that the head "probably has dusky eyes and bill, greyish head... "

Lesser Yellow-heads are very similar to Turkey Vultures, being in the same genus. You can see that the base head-skin color of our immature is like that of the Turkey Vulture perching a few trees away at https://www.backyardnature.net/n/11/111009yw.jpg

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BLACK BELLY/ WHITE BELLY
Black-bellied Plovers are fairly common along the beach nowadays, and most at this time of year have white or almost-white bellies, not black ones. Some of our white-bellied Black-bellied Plovers are seen at https://www.backyardnature.net/yucatan/bbplover.htm.

Field guides assure us that during summer nesting season in the high Arctic of northernmost Canada and Alaska, Black-bellied Plover bellies as well as chests and parts of their faces are indeed broadly and starkly black. The underparts of some of our currently arriving birds are in a state of transition. You can see such a bird with vanishing black underparts at https://www.backyardnature.net/n/11/111009pl.jpg.

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A MUD-TURTLE'S BARBELS
Several times we've run into Red-cheeked Mud Turtles, which I'm thinking must qualify as the Yucatán's second-most common turtle, after the Red-eared Turtle. Our main Red-cheeked Mud Turtle page is at https://www.backyardnature.net/yucatan/mud-turt.htm.

I don't pick up turtles, not wanting to upset them, but this week I was with some visitors who just had to see one at eye level, so they picked up a Red-cheeked Mud Turtle found crossing a road during a nature tour. You can see a nice close-up of the face at https://www.backyardnature.net/n/11/111009tu.jpg.

That picture very nicely shows four tiny, fingerlike, fleshy projections dangling from the turtle's throat area. Those are "barbels," which occur on many species of fish and turtles. A catfish's whiskers are barbels. When identifying fish and turtles, often the number and placement of barbels serve as good field marks.

You can imagine that barbels provide some kind of touch guidance as the turtle forages atop the mud in dark, muddy water, but it seems that they're capable of much more than that. Turtle barbels contain olfactory nerve endings, which means that the barbles are used for smelling. Turtles on dry land can smell odors as we do, but in water turtles with such barbels have this extra odor-sensing method. As the turtle scoots its chin atop submerged mud, through its barbels it's smelling what passes below it.

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APPLE SNAILS
The other day a visitor carried into the kitchen a cooler of snails he'd just gathered from nearby Lake Bacalar. He wanted them cooked. The snails are shown at https://www.backyardnature.net/n/11/111009sn.jpg.

That's Helado the Dog, the one I have to scratch each morning before I jog, nosing into the cooler. A close-up showing two 1-½-inch long snails (4cm) in my hand is at https://www.backyardnature.net/n/11/111009so.jpg

Some snails were white, some very dark, and some were white with splashy dark markings. With my fingers holding the "door," or operculum, of one snail open, its tiger-striped flesh could be seen, as shown at https://www.backyardnature.net/n/11/111009sp.jpg.

I'm assured that these are small ones, and read that they grow to about 2.3 inches across (6cm). A friend living in the town of Bacalar on the mostly-freshwater lake of Bacalar tells me that as a child she loved picking up buckets of such big, white snails and eating them raw along the banks, with lime juice. For the guests here the snails were cooked and served in ceviche, a dish typically made from fresh raw fish marinated in citrus juices such as lemon or lime and spiced with chili peppers and seasonings like onion, salt, cilantro, and pepper.

One name for these snails is the Mexican Apple Snail. In Spanish they're sometimes called Caracol Manzana Maya, or Mayan Apple Snail. They're POMACEA FLAGELLATA, found from Southern Mexico through Central America to northern Colombia. Several species of apple snail -- of the genus Pomacea -- are recognized.

Among conchologists, or mollusk experts, apple snails are thought of as tropical and subtropical, freshwater snails highly adapted for regions with well defined dry and wet seasons. One adaptation is the hard, smooth, close-fitting operculum that closes the shell's hole against drying when the snail withdraws into its shell. Apple snails also have a lung/gill combination for breathing, one for air, the other for water. They stay submerged during the day, hiding in vegetation near the bank and the surface or buried in the mud. During the night they may leave the water looking for fresh vegetation.

Apple snails are known for their edibility and some species are sold to aquarists, who say that more than anything they love to eat zucchini and leafy vegetables such as spinach and lettuce. There's a whole website dedicated just to apple snails at http://www.applesnail.net/.

A 1978 paper by Moholy-Nagy in the journal American Antiquity documents the management of apple snails as a significant food source by the ancient Maya in northern Guatemala.

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ORCHID AT THE MANGROVE'S EDGE
Along a levee's weedy sides right where the paved road entered the mangrove a small colony of terrestrial, pink-flowered orchids showed up. You can see one knee-high clump with stiff, tough, palm-like leaves at https://www.backyardnature.net/n/11/111009or.jpg.

Up close the flowers' main field marks included three rosy sepals spreading widely from the flowers' bases, like a trillium. In the flower's center, notice how the petals form a "hood" over the "column," or "gynostemium" (fused male and female sexual organ found atop the "lip"), and how that three-lobed lip's upper surface is so deeply ridged and frilly, as shown at https://www.backyardnature.net/n/11/111009os.jpg.

A lateral view of a flower with side petals removed showing the above details from a different view is at https://www.backyardnature.net/n/11/111009ou.jpg.

Fruit pods already dangled from some stalks, as shown at https://www.backyardnature.net/n/11/111009ot.jpg.

Among the English names for this species are Purple Bletia, Pine Pink, and Sharp-petaled Bletia. It's BLETIA PURPUREA.

Though all our flowers displayed the same rosy color shown the photograph I read that flower color ranges from pink to deep purple, to almost white. The plants are thought of as terrestrial or semi-epiphytic.

Purple Bletia is a fairly widely occurring species, found from southern Florida -- where it's listed as Threatened -- south through Mexico, Central America to Brazil in South America. It specializes in living in pinelands, hammocks, humus atop limestone, and in swamps like our mangroves, where often it's found on logs, stumps, and tree bases well above the high water mark. It flowers sporadically all year.

A vegetative peculiarity of the species is that it produces pseudobulbs at the base of their leaves, but they're subterranean. Pseudobulbs are succulent water-storage growths some orchid species produce while others don't.

Interestingly, Purple Bletia is known to sometimes produce flowers that don't open, resulting in self-pollination instead of insect-facilitated cross pollination. A writer in Florida says that "many, many" Purple Bletias found in a field there were closed, or "cleistogomous" and thus self-pollinating.

The suggested cause of this high rate of cleistogamy was that southern Florida lies at the extreme northern point of Purple Beltia's distribution and as such may lack enough appropriate pollinators for effective pollination. Through normal evolutionary processes the species may have adapted to the situation by trending toward a high rate of cleistogamy, despite the fact that such a strategy results in clone-like populations with reduced genetic diversity.

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SEA SPURGE
Regularly, usually in weedy spots, we run into smallish, ground-hugging herb species that "bleed milk," or white latex, when injured, and whose flowers display a weird and distinctive anatomy. If you know your wildflowers and weeds you can guess that we're talking about the euphorbias, the most famous of which is the Christmas Poinsettia.

The strange thing euphorbia flowers do is to banish their ovaries -- the future fruits -- to the tip of a stalk projecting clear outside the cup formed by the flower's calyx and corolla, the "cyathium." In a "Wild Poinsettia" found in Chiapas we got a good picture of that. The outcast ovary -- the part labeled "pistillate flower" in the picture -- is shown at https://www.backyardnature.net/chiapas/poinsett.htm.

Recently we looked at a softly herbaceous euphorbia with lush, emerald-green leaves, flowering near the downspout of the employee dorm here. It's still seen at https://www.backyardnature.net/yucatan/euphorb.htm.

Nowadays along our white-sand beach, where salt-spray makes it especially hard for other plants to survive, there's an ankle-high, much-branched, semi-woody, spreading, ground-hugging euphorbia flowering, as seen at https://www.backyardnature.net/n/11/111009ed.jpg.

In that picture those are washed-up coconuts, for scale. Also, notice that this euphorbia's leaves are silvery green, not deep green like the downspout one. A closer shot, showing little leaves neatly aligned along each side of a semi-succulent stem is shown at https://www.backyardnature.net/n/11/111009ee.jpg.

The obligatory showing those crazy ovaries on their stalks hanging outside their cyathia is seen at https://www.backyardnature.net/n/11/111009ef.jpg.

One reason I keep returning to these euphorbias is that I really like the "variations on a theme" thing. The euphorbias came up with something unique that worked for them, and then they went wild with their concept. Wikipedia's euphorbia page says that there's 2008 species of them. There are so many variations, but they all display the same fundamental euphorbia- flower strangeness...

Euphorbias in general often are referred to as spurges. Our beach species sometimes is called the Caribbean Sea Spurge, but the USDA names it Coastal Beach Sandmat. It's EUPHORBIA MESEMBRIANTHEMIFOLIA, mesembrianthemifolia meaning "having leaves like Mesembryanthemum, which is a South African wildflower with leaves like our plant, but large, gaudy flowers as well. Caribbean Sea Spurge is native to southern Florida, the Caribbean, coastal Central America and northern South America.

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MANGROVE MUD
In the mangroves I sat watching for crocodiles as rain moved in off the Caribbean. Below me, splashing raindrops prettily scored orange water, as shown at https://www.backyardnature.net/n/11/111009mg.jpg.

Water in the mangroves often is brightly orange because of tannic acid from mangrove trees. Tannic acid protects the trees from wildfire, decomposition and insect infestation. For humans tannin is an important dye or stain, for wood, leather and other things. Mangroves often grow along the coast next to coral reefs, where darkened mangrove water escaping to sea serves as a sunscreen, protecting the reef's creatures from too much ultraviolet radiation. You can read more about the mangroves' importance to coral here.

But, that day, as I sat in the rain, the mangrove water's bright orange color wasn't the main thing catching my attention. It was the odor of gases escaping from mangrove mud, the heavy, heavy odor of rotting eggs.

Mangrove mud is rich in nutrients but low in Oxygen. Only the first few centimeters of surface mud are oxygenated by burrowing animals. Decomposition of fallen leaves, stems and animal bodies, then, mostly is anaerobic, which means that sulfur is reduced to hydrogen sulfide, better known as rotten egg gas, instead of oxygen being reduced to hydrogen oxide, which is water. Methane also is produced, but that's odorless, and mangrove ecosystem has ways of trapping and holding methane, until someone disrupts or destroys the mangroves, which releases enormous quantities of it.

The combination of hydrogen sulphide with iron compounds give the mud its characteristically black color.

What a stink, but how beautiful it was to sit in the rain deep inside the mangroves, waiting, waiting, waiting for crocodiles.

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UNCLE BEAR'S GOLDEN 300
This week I awarded Gary in North Carolina, aka Uncle Bear, a "Golden 300" award for having identified 300 species in his own neighborhood. If you don't know about my Golden Leaf Awards, which anyone can try for, check out https://www.backyardnature.net/awards/.

For Uncle Bear this started out as just something interesting to do, but my impression is that identifying so many species around his own home has enriched and maybe even changed him. He certainly seems to have enjoyed the process. Of course this was the idea for setting up the awards. When you start paying attention to Nature, Nature speaks to you, and changes you for the better.

Uncle Bear's list of 300 neighborhood species is at https://www.backyardnature.net/awards/g-nc-001.htm.

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LOOKING AT THE OCEAN
When I'm at the beach looking into the ocean, often the same train of thought comes to me. It begins with the usual person-alone-on-the-beach questions, namely, "Why am I here?" and "What should I be doing with my life?" Then always in the same order the following insights occur, like Catholic meditations at Stations of The Cross. They are:

Moreover, at the ocean's edge, there's this:

Once, as I stood in inch-deep water gazing into the ocean, all around my feet the water suddenly exploded into silvery, sparkling sun-splatter as hundreds of minnow-size fish shot from the water and seemed to stand on their tails dancing. In about five seconds that mysterious, voluptuous outbreak of life ended as fast as it had begun and all the fish simply vanished, leaving me dumbly agog.

Another time, exactly where I was gazing, in shallows maybe a hundred feet out, another school of silvery fish started jumping from the water, but this time the fish were about a foot long, and it was clear why they were jumping: Something big swam very fast in a tight circle below them, throwing up very large waves. Barracuda, shark... ? Then all was quiet, so deathly quiet, as the circle of waves spread, dissipating, eventually lapping onto the sand at my feet.

So, it seems to me that the ocean draws us into a clean, methodical, rational thought process, and then Nature fine-tunes our experience until we're pretty sure we're seeing things clearly, seeing things exactly as they are, tail-dancing fish and barracudas included.

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Best wishes to all Newsletter readers,

Jim