JIM CONRAD'S
NATURALIST NEWSLETTER
Issued from Mayan Beach Garden Inn
20 kms north of Mahahual on the Yucatan Peninsula's eastern coast just north of the Belize border, in the state of
Quintana Roo, MÉXICO
(N18º53'17", W87º38'27" )

October 16,  2011

NEEDLEFISH
Along the beach beside Turtlegrass shallows with calm water, often less than ten feet out very slender, pale, foot-long fish with long, needlelike snouts swim alongside me as I walk. They accompany me too often for it to be coincidental; I'm convinced that they're curious about me, or at least somehow think it's a good idea to tag along next to me. Maybe, like Cattle Egrets hanging around livestock that stir up insects as they walk, these fish hope to catch smaller fish my passage scares into deeper water.

I'm figuring that these super-slender fish are Atlantic Needlefish, STRONGYLURA MARINA. Several needlefish species exist, but they mostly keep to deeper water near the reefs, plus, pictures of them on the Internet show slightly different fin shapes and dispositions. Atlantic Needlefish are fairly common in Western Atlantic coastal waters from Maine to southern Brazil, and that includes the Gulf of Mexico and Caribbean. A fish holding something dark in his mouth is at http://www.backyardnature.net/n/11/111016ne.jpg.

Apparently the foot-long individuals who swim beside me are small, immature ones, for adults can reach at least 44 inches (111cm). I read that the diet of juveniles is heavy on small crustaceans and other non- fish animals, but adults are exclusively fish-eaters. In turn, Atlantic Needlefish are eaten by fish larger than themselves, plus, since they are surface swimmers, certain birds prey on them.

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WINTER SWALLOWS
Tree Swallows visit Mexico and Central America only during the Northern cold season. Lately they've been showing up here, as shown at http://www.backyardnature.net/n/11/111016sw.jpg.

All-white underparts, including the throat, distinguish Tree Swallows from other Yucatán swallow species, except for Mangrove Swallows, who are stubbier and have white rumps -- rumps on a bird being the lower back. In the Yucatán we have eight swallow species, of which only three stay year round.

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YELLOW WARBLER
Yellow Warblers are fairly common and very variable. You're lucky if you spot an adult male in courtship plumage because the bird's rusty-red streaking on his yellow chest is distinctive. This April we had just that up at Hacienda Chichen, as shown at http://www.backyardnature.net/yucatan/yellwarb.htm.

The Yellow Warblers I'm seeing here now lack that streaking. They're just very nondescript, nervously flitting, yellowish little birds void of all striking field marks, like what you can see at http://www.backyardnature.net/n/11/111016wb.jpg.

Actually, if you look closely you can see slight remnants of streaking on that bird's chest. That bird was one of a pair of similar-looking ones met working along the edge of a mangrove swamp the other day.

This summer I've commonly seen (but couldn't photograph) spectacularly different-looking Mangrove Warblers, which look like typical Yellow Warblers except that the entire heads of adult males look as if they've been dipped in rust-colored paint. Depending on your expert, Mangrove Warblers constitute one of 35 different Yellow Warbler subspecies, or else they form a distinct species.

Typical Yellow Warblers are present in our area only during the Northern winter, but Mangrove Warblers are permanent residents here along the coast.

So, does the picture show an immature or female typical Yellow Warbler just arrived from up North, or an immature or female Mangrove Warbler? I'm not expert enough to know. Maybe someone out there can say.

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ARMY ANT NOTES
Often we've commented on army ants. Sometimes they travel in broad waves, other times in narrow lines a few ants wide. The other day on the white sand road I biked upon a battalion of them streaming across the road in three or four lines that merged and separated from one another like intersecting superhighways. You can see them, flowing from right to left, at http://www.backyardnature.net/n/11/111016aa.jpg.

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A COCONUT FLOATS ASHORE
The other day a coconut floated ashore. It's shown drifting amidst uprooted Shoalgrass and trash at http://www.backyardnature.net/n/11/111016cc.jpg.

It's possible that that coconut had been dropped into local water earlier that morning, but trash floating with the coconut bore labels identifying points of origin as Venezuela and Trinidad. I'm betting that our coconut fell into the water on the northern coast of South America, or an island of the Lesser Antilles.

Years ago I was taught that Coconut Palms, COCOS NUCIFERA, were native to tropical coastlines worldwide, and thus that they were among the few flowering plants that had no one particular homeland. Now genetic sequencing reveals a different evolutionary history. Most Coconut trees belong to one of two genetically distinct groups. One population arose along the Indian Ocean coastline, the other in the Pacific, from the Malay Peninsula to New Guinea. The species was domesticated in both places, and since then much crossbreeding of the two strains has taken place.

Coconut Palms in Middle America mostly derive from the Pacific domestication while Caribbean palms mostly come from the Indian group. In Mexico it's important to take into account the various genetic groupings because some are much more vulnerable than others to Lethal Yellowing Disease (LYD), which we discuss at http://www.backyardnature.net/yucatan/lethal.htm.

The problem in the Yucatán is that for decades people have been planting just one genetic type known to quickly produce large, round nuts. Unfortunately, that type is very vulnerable to LYD.

So, that smallish, not perfectly round coconut that floated in the other day probably represented Nature's effort to undo the mess caused by people obsessively planting just one Coconut genotype here. Nature is trying to introduce healthy genetic diversity where humans have created a monoculture vulnerabile to diseases.

Not up the beach from here a certain coconut that's floated in from who-know-where has germinated in a pile of moist Turtleweed and trash washed up by the waves. You can see it issuing its first fronds at http://www.backyardnature.net/n/11/111016cd.jpg.

You can see smallish, narrow-type coconuts on a healthy, wild tree -- as opposed to large, spherical coconuts on nearby sick, planted trees -- at http://www.backyardnature.net/n/11/111016ce.jpg.

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MALE & FEMALE WILD PAPAYAS
Those big papayas we buy in markets grow on cultivated trees developed horticulturally from Wild Papa tress, CARICA PAPAYA, which are native to the American tropics. In fact, Wild Papaya trees are among the most eye-catching species along our white sand road because they are so unlike other trees with their big, umbrella-like leaves arising atop thick, succulent, mostly unbranched trunks. Two Papaya trees are shown at http://www.backyardnature.net/n/11/111016pp.jpg.

Notice that flowers on the tree at the left grow at the end of long, branched stems. That tree is male. Flowers on the tree at the right arise directly from the trunk, and that tree is female.

It happens that three types of Papaya trees are recognized based on flower type: male, female, and hermaphroditic, or bisexual. Female plants produce blossoms bearing stigma, style and ovary, but lack pollen-producing stamens. If no male or hermaphroditic plants are nearby to provide pollen, female plants may fail to set fruit, though unpollinated female plants sometimes set parthenocarpic fruits lacking seeds.

Male plants usually produce no fruit.

Hermaphroditic plants may produce both male and bisexual flowers, depending on environmental conditions and the time of year. Hot, dry weather can cause the ovary not to form, resulting in male flowers.

You can see on the female tree at the right in the picture that the fruits -- the papayas -- are about the size of golf balls. On wild trees that's about as large as they get. When they turn orange they'll be edible and the flesh will taste OK, but there won't be enough flesh for most people to bother with. Birds, though, especially woodpeckers, love eating them.

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WHITE TWINEVINE FLOWERING
Along mangrove edges there's a robust, high-climbing vine conspicuously flowering nowadays. You can see a tangled clump of it about 20 feet up a big snag at http://www.backyardnature.net/n/11/111016cl.jpg.

An umbel -- a flower cluster with blossoms on short stalks of equal length arising from a common point -- of its fragrant, white, pea-size flowers is shown at http://www.backyardnature.net/n/11/111016cm.jpg.

A close-up of the vine's very distinctive blossom is at http://www.backyardnature.net/n/11/111016cn.jpg.

If you're familiar with wildflowers you may recognize the blossom's general design as being that of the milkweeds. We have a page on milkweed flower structure at http://www.backyardnature.net/fl_milkw.htm.

The main English name for this vine seems to be White Twinevine. It's FUNASTRUM CLAUSUM, a member of the old Milkweed Family, which lately has been lumped into the big Dogbane Family we've met so frequently, in which oleander, frangipani, allamanda, periwinkle and others also are found.

Maybe you remember that most members of the Dogbane Family exude white latex if injured, and that that latex often contains poisonous chemicals. White Twinevine is especially milky-juiced. In Jamaican folk medicine the plant is used as a remedy for colds, while in Costa Rica and Guatemala poultices are made from the plant's crushed leaves and used to kill flesh-burrowing maggots of the Human Botfly, Dermatobia hominis.

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GOATWEED BOTANY
The other day Newsletter reader Harald here in the Yucatán sent me a plant picture to identify, a plant that showed up in his garden unannounced, a species that had just begun flowering along our road, too. I didn't know it so I had to "do the botany on it" to figure out its name. You can see the knee-high plant's white, pea-sized flowers and saw-toothed-edged leaves at http://www.backyardnature.net/n/11/111016gw.jpg.

A flower close-up with the nearest of five petals removed so we can better see the flower's five stamens and, at the bottom of the flower, a little green ovary topped with a long, slender style ending with a burry, egg-shaped stigma above the stamens' white anthers is at http://www.backyardnature.net/n/11/111016gx.jpg.

Certain field marks reveal this as a member of the Figwort or Snapdragon Family, the Scrophulariaceae. An important field mark is that the five-stamened flower is very slightly asymmetrical, with bilateral instead of radial symmetry. Also, the fruits are dry capsules that split to release many seeds, which is typical of the Figwort Family. Once I knew the family I checked the Flora of Quintana Roo, the Mexican state I'm in now, to see what species in that family are present here. The Flora of Quintana Roo is available online at http://www.ibiologia.unam.mx/BIBLIO68/fulltext/lfl2.html.

By doing an image-search on the Figwort Family species in Quintana Roo I didn't recognize, soon I came up with a match. Our plant is CAPRARIA BIFLORA, in English sometimes known as Goatweed. It occurs from southern Florida and southern Mexico through much of the Caribbean and Central America into South America.

Harald was tickled with the name because when he looked it up on the Internet he found that the plant often is considered medicinal, and Harald likes medicinal plants. A website on the island of Saint Lucia says that there a tea of Goatweed -- called Dité Peyi there -- is believed to help people adapt to severe changes of weather. A tea made of a small branch is drunk three times a day for gas. Another website, in Mexico, which calls it by its Maya name Chokuilxim, says that it's good for "matrix bleeding and white refluxes," whatever they are, and acne.

It's very unusual to find detailed taxonomical works on the plants of this area, but an illustrated treatment of the genus Capraria in the Yucatan Peninsula can be downloaded for free, in PDF format, at http://redalyc.uaemex.mx/pdf/577/57707906.pdf.  

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LEATHER FERNS
At high elevations we've run into tree ferns, so we're familiar with big ferns. However, the big fern found at the edge of a mangrove swamp the other day was notable for its large size because it wasn't a tree fern. It was just a really big fern growing on the ground the regular way. You can see part of a frond at http://www.backyardnature.net/n/11/111016lf.jpg.

The fern grew in dense brush so I couldn't step back for a picture of the whole eight-ft-tall plant. Some frond sections, or pinnae, were producing heavy crops of brown spores on their lower surfaces, as shown at http://www.backyardnature.net/n/11/111016lg.jpg.

This is a Leather Fern, genus Acrostichum, a genus distinguished by the large size of its species, by the species' swampy, marshy habitat preferences, and by the way abundant spores are produced across the whole lower surface of pinnae instead of in neat little "fruit dots" like those we've seen on most ferns we've encountered.

Two species of Leather Fern are found in our area: Acrostichum aureum and A. danaeifolium, and they're fairly similar. Spore-bearing pinnae of A. aureum are limited to the fronds' topmost pinnae, while on A. danaeifolium spore-bearing pinnae occur throughout most of the frond. The latter seemed to be the case with our plant, so I'm thinking that our photo shows Acrostichum danaeifolium. More distinctions are given on the Flora of North America Acrostichum page here.  

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COASTAL LAGOONS
If on Google Earth you search for "Mayan Beach Garden" you'll see that just inland here all along the coast there are fair-sized lakes. Some are practically inaccessible but others are near the road and trails have been cut to them. The other day I visited the one at http://www.backyardnature.net/n/11/111016lk.jpg.

At the left, those are Red Mangrove "stilt roots." Notice the little island a bit behind the roots. Mexican fishermen I met there told me that recently they'd seen a big flock of Flamingos on the island but the only birds I saw that day were a kingfisher and a Green Heron.

These lakes are more specifically referred to as coastal lagoons. The Google Earth view from space makes it easy to imagine how such lagoons form. You start out with an irregular shoreline, then the ocean's currents always flowing in the same direction deposit sediment across any bay's mouth, closing it off, forming a lagoon. The sand ridge we occupy at Mayan Beach Garden is such a deposition, and there are lagoons not far inland.

Coastal lagoons typically fill with brackish or saline water. Salinity of water in our lagoons tends to be low, however, since freshwater enters the lakes from subterranean rivers carrying water from inland. Still, at a certain level you get saline water and saline water intrudes during the dry season, so salinity in our lakes varies. Here at the peak of the rainy season our lagoons aren't very salty at all.

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WELCOME MIGRANTS
It was good seeing this week's bird migrants recently arrived from North America. Back in the early 60s as I was becoming sensitized to Nature, experiencing spring and fall migration in western Kentucky on the Mississippi Flyway was gloriously transformative. Colors, sounds and feelings washed around me as if Nature Herself were speaking to me face-to-face.

But, in my lifetime the sheer numbers of most but not all neotropical migrant species has diminished and I wonder if anyone nowadays can experience what I did back then. A summary of the situation in PDF format is provided for free by the US Fish & Wildlife Service here

I try not to dwell on charts in that publication showing drops in migrant numbers. When destruction and ignorance around us become too great to bear, just to save your sanity sometimes instead you need to focus on and identify with the eternal Universal Creative Inspiration out of which birds, their migrations and everything else arose in the first place.

If you identify with the Universal Creative Inspiration you can even find some comfort in the fact that 286-248 million years ago, at the end of the Permian Period, a mass extinction of life on Earth occurred in which between 75 and 95 percent of the Earth's species, including nearly all animals, disappeared. Several other extinctions nearly as bad also have occurred. Yet, today, despite what the current trends are, there's much more biological diversity than just before the Permian Extinction, and more natural beauty and mystery than human minds can handle.

So, maybe the numbers of migrating warblers will continue to plummet, and maybe most warbler species will go extinct, but nothing will change with the Universal Creative Inspiration. Evolution will continue, even if it has to start over. And someday, once again, evolving colors, sounds and feelings will wash around thinking, sensitized life forms -- whether human or not -- with even more gorgeous vitality than bird migration visited upon me on the Mississippi Flyway back in the early 1960s.

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Best wishes to all Newsletter readers,

Jim