July 24, 2011
Earlier that morning on the white sand road paralleling the beach I'd come upon a seven-ft (2m) Boa Constrictor, so it was fitting that now the snake my bike almost had run over hardly was the length of my finger, and was slender as a matchstick, as seen at http://www.backyardnature.net/n/11/110724sn.jpg.
The snake was so slender that I couldn't pick him up without being so rough I might hurt him, so he wiggled away without my getting the head picture often needed for proper identification. However, maybe that wasn't such a great loss, because with the snake's distinctive tan collar and nose tip, surely it'd be easy to identify.
And it was: It's the Mayan Black-headed Centipede- eater, TANTILLA CUNICULATOR, endemic to the northeastern half or two thirds of the Yucatan Peninsula, northern Belize and northern Guatemala. In Amphibians and Reptiles of Northern Guatemala, the Yucatán, and Belize, Jonathan Campbell writes that the snake reaches 25cm, or ten inches, so apparently our little snake is a very young one.
Campbell also describes the species as secretive and inhabiting tropical moist and dry forests, where presumably it feeds on invertebrates. Actually, few details are supplied for the species, and there's not much more on the Internet. Maybe we're contributing something to science here just by reporting that sometimes in our part of the world Tantilla cuniculator can be found crossing a sand road in bright, mid-afternoon sunlight.
BIRDLESS BEACH, BIRDLESS FLATS
During the Northern winter the beach here in the southeastern Yucatán stays busy with Laughing, Herring and Ring-billed Gulls, and Royal, Caspian, Sandwich, Forster's and Gull-billed Gulls. Of plovers there are the Snowy, Wilson's, Semipalmated, and the Killdeer. There are Willets, Red Knots, Whimbrels, Sanderlings, and Ruddy Turnstones, and among the sandpipers are the Spotted, Western, Least, and also dowitchers and snipes, and other long-legged, beach and shallows- loving species passing through only during spring and fall migration.
Thing is, nearly all the above species are listed as winter visitors for this part of the world. Wilson's Plovers are permanent residents, but they seldom show up here. In fact, right now -- too late for spring migration and too early for fall migration -- there's blessed little for birders to see along our beaches and in shallows and flats.
You see Magnificent Frigatebirds, a few Brown Pelicans and an occasional Royal Tern. Sometimes pairs of fast- flying boobies with tapered tails and very long, slender, bent wings speed by but I can't see which species they are. A few weeks ago we found that dying Red-footed Booby at the rocky point just below us, so maybe they're Red-footeds.
In general, the absence of birds in seemingly biologically rich environments is astonishing. Horizon-to-horizon heaps of moldering seaweed wash up along shore work with those plump springtails we looked at awhile back, so why aren't sandpipers and plovers probing those heaps with their long bills, feeding on springtails? The Turtlegrass shallows at low tied are perfect hunting grounds for long-legged herons and egrets stalking small fish, but none are to be seen there. Why not?
Well, clearly species migrate away from this area during the sumer, but why didn't species evolve taking advantage of these rich feeding grounds available here right now?
One answer I can come up with, by guessing, is that it's a dangerous strategy for any species to nest in an area so vulnerable to hurricanes.
SAND COUCH GRASS
Where the narrow, white-sand road meets the beach, usually there's a certain ubiquitous, clump-forming grass producing runners that inch onto the road until they're pruned by car tires. A knee-high population issuing slender, pale flowering heads is shown at http://www.backyardnature.net/n/11/110724gr.jpg.
A close-up showing a runner rooting at its nodes and issuing short stems with short, stiff, congested, sharp-pointed leaves and dense, cylindrical, flowering heads (spike-like panicles) can be seen at http://www.backyardnature.net/n/11/110724gs.jpg.
This is SPOROBOLUS VIRGINICUS, native to the tropical and warm Americas from the US southern states south to Chile and Brazil. It's been naturalized in so many other countries in Africa, Asia and Australasia that it's known by many English names, including Marine Couch, Sand Couch, Coastal Rat-tail Grass, Salt Couch Grass, Saltwater Couch and Seashore Dropseed.
Mostly the grass grows on sandy, salty, mostly coastal soils. With those node-rooting runners shooting across the sand and the concentration of leaves close to the ground, it's clear why this grass is a very important member of the coastal strand community: It gathers windblown sand, slowing beach erosion. Sand Couch is an important species in worldwide beach restoration projects, where plants have to be highly salt tolerant, and able to impede wind-blown sand.
There's a similar species in some parts of the world occurring in the same habitat -- Distichlis spicata. One way to distinguish the two species is by the flowers. Distichlis spicata's florets bear conspicuous green lines, or "ribs," along their sides, while Sand Couch florets lack those ribs, as shown at http://www.backyardnature.net/n/11/110724gt.jpg.
It's interesting that several of the English names for this plant include the word "couch." A little digging into the word's etymology reveals that using "couch" for grasses goes way back, the first mention of "couch-grass" being made back in the 1570s. The word was corrupted from the Old English "cwice," which meant "living" or "alive," and arose, presumably, from Proto-Germanic "kwikwaz." Maybe in earlier times "Couch-Grass" seemed particularly "alive" because it could thrive in salty, severe beach habitats.
Capulín is a name used for a number of cherry-like trees. One of those Capulines is a common, almost weedy tree commonly seen along roadsides here. In the Hackberry Family, it's TREMA MICRANTHA. Nowadays they're loaded with pea-sized fruits, as shown at http://www.backyardnature.net/n/11/110724tr.jpg.
In the genus Trema, flowers are mostly unisexual, with male and female flowers usually on the same plants, plus sometimes there are bisexual blossoms -- flowers with both male and female parts. You can see a male one at http://www.backyardnature.net/n/11/110724ts.jpg.
In the Hackberry Family flowers lack corollas and petals, so in the picture the five scoop-shaped, green things are the calyx's hairy-backed sepals. Each sepal subtends a greenish, pollen-producing stamen.
The fruits are fleshy drupes containing large, hard pits, and are much appreciated by certain fruit-eating birds, such as our most common one here, the Tropical Mockingbird.
MANGROVES SLOWLY FILLING WITH WATER
With the rainy season's gradual arrival, slowly large parts of mangrove swamps that until now have been dry are slowly filling with water. You can see a tangle of head-high Red Mangrove, Rhizophora mangle, that a month ago stood upon dry, caked mud at http://www.backyardnature.net/n/11/110724hy.jpg.
After a good rain the water rises higher, as you'd expect. However, if you really pay attention over a period of time, gradually the feeling grows that sometimes the water's average depth increases faster than the rains would seem responsible for. Also, if several dry days come along, the water may stand longer than seems reasonable. The impression is that something in addition to local rains is contributing to the mangroves' water-level rise.
Many studies show that that's the case. Remember that the Yucatan Peninsula is a vast slab of limestone eaten through and through with caves which, if occurring below the water level, carry underground rivers. In the northern and central peninsula, there are no surface rivers or streams. During the rainy season, rainwater quickly seeps underground along fractures in the limestone, into sinkholes and caverns, and merges with the water table.
The Yucatán's subterranean streams flow outward toward the nearest sea. Since the peninsula pokes northward into the zone of aridness at ±30°N we've considered at here, in the Yucatán it's much rainier in the south than in the north. Thus the general flow of freshwater in the Yucatán's underground rivers is both from south to north, as well as outward toward the coasts.
In short, those big storms I've been mentioning that most afternoons form inland but usually stay away from us on the coast, plus the even larger, more intense storms forming farther south, especially in Guatemala, are contributing to the increasing water level in our mangroves. In our mangrove picture you can see that the water is reddish. I'm guessing that the redness is tannic acid leached from Red Mangrove leaves decomposing in the mud, through which much of the standing water has filtered upwardly after its long subterranean journey up from Guatemala.
By the way, the freshwater seeping into the mangroves nowadays creates a thin lens floating atop deeper saltwater. When the rainy season ends, not only will the mangroves' water level drop, but also saltwater will intrude into places where previously there was freshwater -- as in certain wells of homes here along the coast.
The freshwater/saltwater interaction is complex and sometimes unpredictable. You might enjoy looking over the paper "Freshwater Resources in the Yucatan Peninsula" freely available online, at http://www.nap.edu/openbook.php?record_id=11875&page=6.
ENCHANTMENT OF PALMS
Enchantment is magical resonance between what's outside a person, and what's inside. As a teenager I was enchanted by a swampy woods near our family's farm in Kentucky. I sat on a log speechless as the forest's colors, odors, sounds, structure and processes meshed with and nourished similar but less developed features and impulses already within me. The forest shared its strength and beauty, some of which I still carry within me.
As it should be, enchantments are more frequent and more powerful for the young than the old. Still, anyone can be enchanted at any age. In fact, this week I experienced a modest one that even still has me glowing.
It was an enchantment with palm trees. That's odd, because I've been around palms most of my life, so why become enchanted now? Maybe I just needed the right catalyst. This week the catalyst was an inflorescence of palm flowers opening at eye level 15 feet up a Coconut Palm beside my second-story porch. It was dusk and the sun was setting behind me, warmly illuminating the palm. You can see that very inflorescence at http://www.backyardnature.net/n/11/110724pm.jpg.
That picture doesn't convey the effect of the tree's rustling and clacking fronds quivering and twisting in the wind, doesn't show how the silhouetted fronds' surface-gleams shifted here and there as big petioles flexed and swayed, and narrow pinnae on different fronds overlapped one another, etching in my mind dynamic crosshatchings of light and shadow.
Downstairs, another palm inflorescence opened closer to the ground so I went there. Honeybees hustled up and down the flower cluster's branches seeking nectar in half-open blossoms, as shown at http://www.backyardnature.net/n/11/110724pn.jpg.
Beneath the palms and inside their whispery rustles and woody crepitations, watching the bees, seeing and hearing so many palmy things, I found myself effervescing wood-toned feelings and thoughts, enchanted.
A gift: From my second-story perch expressive palm fronds frame all my views. Here's a picture of the microwave tower beaming this Newsletter on its first leg to you, from here to Mahahual 20kms to the south. Does the enchantment carry, even at this distance? http://www.backyardnature.net/n/11/110724__.jpg.
Best wishes to all Newsletter readers,