JIM CONRAD'S
NATURALIST NEWSLETTER
Written at Mayan Beach Garden Inn 20 km north of Mahahual
on the Yucatán Peninsula's eastern coast just north of the
Belize border, in the state of
Quintana Roo, MÉXICO

December 15,  2008

TWO WADERS
At a spot down the beach a landowner has scalped the vegetation so far from the road that he's created open water with a shallowly sloping mudflat where once dense mangrove stood. Of course that's obliterated species-rich mangrove ecology there but it's also provided a nice place for small wading birds not interested in the sandy beaches right across the rise.

At http://www.backyardnature.net/n/08/081215x4.jpg you see part of a small flock encountered there about an hour after sunrise last Wednesday morning. Wind off the ocean was tremendous and the birds were just standing there basking in the sunlight and leaning into the wind.

The three larger birds with white necklaces are Semipalmated Plovers, CHARADRIUS SEMIPALMATUS, who nest along the northernmost coasts of Arctic North America, but overwinter from the coastal southeastern US south to Chile and Argentina. They're so commonly seen over this huge winter distribution that it's hard to imagine what their population density must be during their brief breeding period in the Arctic.

If you're an inlander North American you might notice the Semipalmated Plover's similarity to North America's Killdeer. They're in the same genus. You'll remember that Killdeer wear white necklaces, too.

The smaller bird up front looks a lot like one of the Sanderlings that that morning were busily foraging on the sandy beach just over the rise from the mudflat, but Sanderlings, as noted last week, generally occur in small flocks on the beach chasing waves in and out. Several small wader species in winter plumage have the Sanderling look and they can be awfully hard to separate in the field. I wouldn't be able to identify it myself, but my friend David Wingate, master of the birds of Bermuda, assures me that it's a Least Sandpiper. "You can distinguish it by its slightly down-turned bill and yellowish legs," he writes.

*****

"SEMIPALMATED"
So here were Semipalmated Plovers with a Semipalmated Sandpiper. That word "semipalmated" is a big one in the birding world. When referring to birds it describes the condition of having the front toes only partly joined with duck-foot-like webbing. It means "half-webbed."

*****

BLACK-BELLIED PLOVERS
At http://www.backyardnature.net/n/08/081215bp.jpg you see a medium-sized plover often seen here hanging out with Sanderling flocks on the beach and with Semipalmated Plovers at the water's edge in the mangrove pond. You know it's a plover because of the slight bulge right behind the short, thick bill's tip, and you know it's a Black-bellied Plover in winter plumage because of the combination of the heavy mottling and the white rump seen when it flies, shown in the inset. The "rump" is where the tail connects with the upper back.

Plovers typically feed in a stop-start manner -- standing still, then running and pecking, then standing awhile, etc. They feed on many kinds of invertebrates. Our bird's big eye also is typical of plovers.

The Black-bellied Plovers I'm seeing here are always the only one of their species staying loosely associated with flocks of smaller, faster-moving shorebirds. Howell says that sometimes you see flocks of over a hundred of them, though.

*****

GHOST CRABS
Just about anytime during the day as you're walking along the beach or the scrubby rise between the ocean and the mangroves, but especially at dawn and dusk, you see the white, black-eyed, fuzzy legged crab shown at http://www.backyardnature.net/n/08/081215cb.jpg.

About the size of a saucer, this is the Atlantic Ghost Crab, sometimes referred to as a sand crab, OCYPODE QUADRATA. You can see in the picture that one of this species' claws is larger than the other. This points to the fact that the genus Ocypode resides in the same family as fiddler crabs, the Ocypodidae, famed for having a single claw so large that it looks like the crab is playing a fiddle.

In the short time I've been here I've learned three things about our ghost crabs. First, they dig deep slanting tunnels into moist sand (four-feet deep, at a 45° angle, I read), and if a favorite ornamental plant stands above the tunnel the digging's disturbance may damage or kill the plant.

Second, ghost crabs eat an enormous variety of foods, such as the blackened, brittle, dried leaf the one in the picture is munching on, and; third:

If you're jogging down a road at dawn and come upon a ghost crab, if it figures it can't outrun you, it'll stand its ground and try to face you down, holding its white claws before it like a judo expert keeping his dangerous hands out front. In dim dawn or dusk light, the white claws are very conspicuous, almost seeming to glow. A good-sized dog wanting badly to sniff the critter, seeing the spectral white claws brandished before him, cedes his sniffing rights.

Many crab species are aquatic, but Ocypode quadrata is beautifully adapted for life on land, only occasionally returning to water to wet its gills. Ruppert & Fox in 1988 published a work describing how the species also can moisten its gills by extracting water from damp sand, using fine hairs near the base of its walking legs to wick ground water up onto the gills through capillary action! The species also must be close to water at mating time, for its females release their eggs at the water' edge.

*****

GOOSE BARNACLE ON AN OIL CAN
The other morning on the beach I picked up a black, plastic container previously containing a quart of oil, and attached to it was the item shown at http://www.backyardnature.net/n/08/081215gb.jpg.

In the picture the shell's left side is attached to the can. If you flip the picture 90? counterclockwise the shell looks like a white butterfly with an orange rim along its upper wing. I felt sure that its name would be something like "Butterfly Barnacle" but when I showed it to a visitor she exclaimed "Oh, you've found a Goose Barnacle."

In an instant I saw what was goosy about it. As it's shown in the picture, doesn't it look like a goose's head, the broad, bulging area at the lower left being the cheek?

After the barnacle had been out of the water awhile, the slit between the orange rims opened a bit and a dark, spidery thing appeared. Those feathery items were the crustacean's modified legs, which in water beat rhythmically to draw plankton and detritus into the shell for consumption.

The barnacle lifecycle is complex, involving two larval stages. You can read about it and see pictures at http://en.wikipedia.org/wiki/Barnacle.

Goose Barnacles are LEPAS ANSERIFERA and they enjoy a worldwide distribution. They're crustaceans.

*****

SEA FANS
Along the beach here often you find what's in my hand at http://www.backyardnature.net/n/08/081215sf.jpg.

That's a dead, stiff "skeleton" of a sea fan of the genus GORGONIA, possibly G. ventalina. Around 50 species are listed so it might be another species. You can see a living Gorgonia ventalina here.

Are Sea fans, or gorgonians, plants or animals? Well, they're known as "soft corals" and you probably know that corals are animals.

Moreover, coral masses consist of communities of many animals, and it's the same deal with sea fans. Sea fan "skeletons" are structures on which live multitudes of individual tiny animal "polyps." Each gorgonian polyp bears eight tentacles, making it look like a tiny octopus with its legs waving in the water. The tentacles catch plankton and particulate matter as the polyps filter feed. You can read much more about sea- fan anatomy and ecology, and see polyps extending their tentacles into the water, at http://en.wikipedia.org/wiki/Sea_fan.

*****

SEAGRAPES
One of the most common and conspicuous shrubs or small trees here on the dry sand rise between the sea and the mangroves -- thus in competition with real-estate- minded humans -- is the species shown at http://www.backyardnature.net/n/08/081215sg.jpg.

That's Seagrapes, COCCOLOBA UVIFERA, easy to recognize by its large, roundish, leathery leaves often ornamented with red veins and splotches, as shown at http://www.backyardnature.net/n/08/081215sh.jpg.

The last picture also shows a detail that helps us recognize which plant family Seagrapes belongs to. Notice the red, collar-like "sheath" surrounding the stem at the base of the leaf's petiole (See the little wolf spider hiding in the sheath?). This sheath is a special kind of stipule, which itself is a special kind of modified leaf.

In most plants with stipules there's an inconspicuous stipule on each side of the petiole's attachment to the stem. Stipules protect tender emerging shoots and flowers as they expand from their buds, and the stipules typically shrivel and fall away once the parts they're protecting are fully developed. In the Seagrapes' family, however, stipules extend all the way around the stem forming this cuplike sheath.

When you see stipular sheathes like this the first family to come to mind should be the Buckwheat Family, the Polygonaceae. In North America the most commonly encountered members of the Buckwheat Family are the smartweeds or knotweeds, often seen in weedy and/or wet places. If you're familiar with the way small smartweed flowers are arranged on spikes you won't be surprised to see what Seagrapes flowers look like at http://www.backyardnature.net/n/08/081215si.jpg.

Actually, that spike has lost nearly all its flowers; it's a bit late in the season to see Seagrapes flowers here. However there's at least one tiny white blossom to be seen in the picture, against the cloud's base.

Up north, Seagrapes produce drooping, grapelike clusters in late summer, each fruit being about 2 cm in diameter (0.8 inch). The fruits contain pits and are enough like grapes for jam to be made of them or eaten straight from the tree. Seagrapes don't grow too far north, however, because they're not frost resistant. They are indeed tolerant of shade, however, are highly tolerant of salt, and ecologically are very important for stabilizing beaches.

*****

MANILA PALM
At http://www.backyardnature.net/n/08/081215pm.jpg you see the handsome, smallish, feather-leafed or pinnate-leafed palm at the entrance to Mayan Beach Garden. Palm fanciers may recognize it as a close relative to the famous, stately, much larger Royal Palm.

This is a much-planted species native to the Philippines, VEITCHIA MERRILLII. Since it's planted so extensively it goes by many names. In the US often it's called Christmas Palm because it produces olive-size red fruits but internationally it seems to be best known as Manila Palm, and of course some call it Dwarf Royal Palm.

At http://www.backyardnature.net/n/08/081215pn.jpg you see a honeybee lifting from one of its flowers. Veitchias are monoecious, which means that on one plant you get unisexual male and female flowers. In the picture you can make out an oval ovary amidst the cluster of pollen-producing stamens, so that ovary must be sterile, because the stamens seem to be doing a good job producing white pollen. Notice the pollen bag on the honeybee's back leg.

*****

TURBINARIA
A while back I showed you a whole beach heaped with washed-up, dead, blackening seaweed, which I identified as Turtle Grass. The day after that Newsletter went out the wind changed and then the next day most of the washed-up, dead, blackening seaweed was something other than Turtle Grass. That was my introduction to the fact that what washes up on this beach can change dramatically from day to day.

You can see the second kind of washed-up seaweed at http://www.backyardnature.net/n/08/081215tu.jpg.

It took awhile to figure out that this was a brown alga of the genus TURBINARIA. Turbinaria turbinata is listed as a common species off the Quintana Roo coast and it looks like that on the Internet. The genus Turbinaria resides in the same family as better-known Sargassum of Sargasso Sea fame. That makes sense because the two genera produce species of similar color and display the same living strategy of floating about in loose, chainlike clusters. The genera are members of the order Fucales, and are known as Brown Algae.

There's a good bit of info on the Internet about the use of Turbinaria species medicinally. A quick scan turns up papers using a species from the Yucatan coast against the Leishmania parasite, and there's another page describing its antioxidant activities.

From what I can read, Turbinaria species can reproduce either sexually or by fragmentation -- small pieces of it "rooting" on submerged rocks. And anything producing such huge amounts of biomass as I saw heaped on the beach that day, just hinting at what remained out in the ocean, is bound to have enormous importance to the oceanic ecosystem.

*****

SLEEPING ON THE BEACH
This week the ever-waxing gibbous Moon increasingly bleached the night sky but, still, one morning about 2 AM when I needed to exit the tent to pee, the tropical night sky was beautiful beyond description. Stars were so bright that it was hard to pick out constellations and each individual star twinkled almost violently. Usually the starry sky looks like a flat, black blanket overhead through which pinpricks of sunlight penetrate, but that night the sky drew me into its profound depth.

Kneeling in the sand at my tent's entrance I grew vividly aware of being a passenger on Spaceship Earth voyaging through space. I was on this little planet surrounded by an enormity of dead, cold emptiness and, beyond that, the innumerable stars of our own Milky-Way galaxy, maybe most of them possessing their own planetary systems, and beyond all those stars lay innumerable completely different galaxies, each galaxy itself engendering innumerable stars, and all those worlds both in our own galaxy and those beyond our galaxy potentially harbored life, or maybe something more wondrous than life.

Long I knelt amidst the voyaging, sparkling animation, the churning, spiraling enormity of possibilities, and I was glad, glad to be witness to what was going on, and humbled to be part of it.

*****

Best wishes to all Newsletter subscribers,

Jim

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

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